XML Fundamentals

Elliotte Rusty Harold

XMLOne Austin

March 5, 2001

elharo@metalab.unc.edu

http://www.ibiblio.org/xml/

Outline

Part I: XML Overview
Part II: What is XML Good For?
Part III: A Practical Example
Part IV: Well-formedness
Part V: DTDs and Validity
Part VI: Namespaces

Part I: XML Overview

What is XML?

Extensible Markup Language
A syntax for documents
A Meta-Markup Language
A Structural and Semantic language, not a formatting language
Not just for Web pages

XML is a Meta Markup Language

Not like HTML, troff, LaTeX
Make up the tags you need as you need them
The tags you create can be documented in a Document Type Definition (DTD)
A meta syntax for domain-specific markup languages like MusicML, MathML, and CML

XML describes structure and semantics, not formatting

XML documents form a tree
Element and attribute names reflect the kind of the element
Formatting can be added with a style sheet

A Song Description in HTML

<dt>Hot Cop
<dd> by Jacques Morali, Henri Belolo, and Victor Willis
<ul>
<li>Producer: Jacques Morali
<li>Publisher: PolyGram Records
<li>Length: 6:20
<li>Written: 1978
<li>Artist: Village People
</ul>

View Document in Browser

A Song Description in XML

<?xml version="1.0" encoding="ISO-8859-1" standalone="yes"?>
<SONG>
  <TITLE>Hot Cop</TITLE>
  <COMPOSER>Jacques Morali</COMPOSER>
  <COMPOSER>Henri Belolo</COMPOSER>
  <COMPOSER>Victor Willis</COMPOSER>
  <PRODUCER>Jacques Morali</PRODUCER>
  <PUBLISHER>PolyGram Records</PUBLISHER>
  <LENGTH>6:20</LENGTH>
  <YEAR>1978</YEAR>
  <ARTIST>Village People</ARTIST>
</SONG>

View Document in Browser

The XML Declaration

At the top of the document, you normally find an XML decalration:
<?xml version="1.0" encoding="ISO-8859-1" standalone="yes"?>
version attribute
- required
- always has the value 1.0
standalone attribute
- yes
- no
encoding attribute
- UTF-8
- ISO-8859-1
- etc.

Elements

Document are composed of elements
An element is delimited by a start tag and a matching end tag:
<COMPOSER>Jacques Morali</COMPOSER>
- Start tag <COMPOSER>
- Contents "Jacques Morali"
- End tag </COMPOSER>

Elements can contain other elements:

<SONG>
  <TITLE>Hot Cop</TITLE>
  <COMPOSER>Jacques Morali</COMPOSER>
  <COMPOSER>Henri Belolo</COMPOSER>
  <COMPOSER>Victor Willis</COMPOSER>
  <PRODUCER>Jacques Morali</PRODUCER>
  <PUBLISHER>PolyGram Records</PUBLISHER>
  <LENGTH>6:20</LENGTH>
  <YEAR>1978</YEAR>
  <ARTIST>Village People</ARTIST>
</SONG>

Style Sheets provide formatting

SONG     {display: block}
TITLE    {display: block; font-family: Helvetica, serif;
          font-size: 20pt; font-weight: bold}
COMPOSER {display: block; 
          font-family: Times, Times New Roman, serif;
          font-size: 14pt;
          font-style: italic}
ARTIST   {display: block; 
          font-family: Times, Times New Roman, serif;
          font-size: 14pt; font-weight: bold;
          font-style: italic}
PUBLISHER {display: block; 
           font-family: Times, Times New Roman, serif;
           font-size: 14pt}
LENGTH    {display: block; 
           font-family: Times, Times New Roman, serif;
           font-size: 14pt}
YEAR      {display: block; 
           font-family: Times, Times New Roman, serif;
           font-size: 14pt}

Attaching style sheets to documents

<?xml-stylesheet type="text/css" href="song1.css"?>

<?xml version="1.0"?>
<?xml-stylesheet type="text/css" href="song1.css"?>
<SONG>
  <TITLE>Hot Cop</TITLE>
  <COMPOSER>Jacques Morali</COMPOSER>
  <COMPOSER>Henri Belolo</COMPOSER>
  <COMPOSER>Victor Willis</COMPOSER>
  <PRODUCER>Jacques Morali</PRODUCER>
  <PUBLISHER>PolyGram Records</PUBLISHER>
  <LENGTH>6:20</LENGTH>
  <YEAR>1978</YEAR>
  <ARTIST>Village People</ARTIST>
</SONG>

View Document in Browser

song.xsl

<?xml version="1.0"?>
<xsl:stylesheet version="1.0"
                xmlns:xsl="http://www.w3.org/1999/XSL/Transform">

  <xsl:template match="SONG">
    <html>
      <body>
       <h1>
        <xsl:value-of select="TITLE"/> 
        by the 
        <xsl:value-of select="ARTIST"/> 
       </h1>
       <ul>
         <xsl:apply-templates select="COMPOSER"/>
         <li>Publisher: <xsl:value-of select="PUBLISHER"/></li>
         <li>Year: <xsl:value-of select="YEAR"/></li>
         <li>Producer: <xsl:value-of select="PRODUCER"/></li>
       </ul>
      </body>
    </html>
  </xsl:template>

  <xsl:template match="COMPOSER">
    <li>Composer: <xsl:value-of select="."/></li>
  </xsl:template>

</xsl:stylesheet>

Applying an XSLT Style Sheet

Browser support is weak to non-existent.
Can use third party tools like Xalan, Saxon, and XT
Let's use Saxon to apply this stylesheet to compositions.xml.
- Windows executable:
  C:\> saxon hotcop.xml song.xsl>hotcop.html
- Java executable:
  C:\> java com.icl.saxon.StyleSheet hotcop.xml song.xsl>hotcop.html

Output

<html>
   <body>
      <h1>Hot Cop 
         by the 
         Village People
      </h1>
      <ul>
         <li>Composer: Jacques Morali</li>
         <li>Composer: Henri Belolo</li>
         <li>Composer: Victor Willis</li>
         <li>Publisher: PolyGram Records</li>
         <li>Year: 1978</li>
         <li>Producer: Jacques Morali</li>
      </ul>
   </body>
</html>

View in browser

Editing and Saving XML Documents

Plain ASCII or UTF-8 text
.xml is standard file extension
Any standard text editor will work

Part II: What is XML Good For?

What is XML used for?

Domain-Specific (Vertical) Markup Languages
Self-Describing Data
Interchange of Data Among Applications
Structured and Integrated Data

Domain-Specific Markup Languages

Markup language for a vertical market
Non-proprietary format
Don't pay for what you don't use

Self-Describing Data

Much data is lost due to format problems
XML is very simple
XML is self-describing
XML is well documented

An XML Fragment

<PERSON ID="p1100" SEX="M">
  <NAME>
    <GIVEN>Judson</GIVEN>
    <SURNAME>McDaniel</SURNAME>
  </NAME>
  <BIRTH>
    <DATE>21 Feb 1834</DATE>
  </BIRTH>
  <DEATH>
    <DATE>9 Dec 1905</DATE>
  </DEATH>
</PERSON>

Interchange of Data Among Applications

E-commerce
Syndication
EAI and EDI

Can assemble data from multiple sources

A document can be assembled from multiple physical storage entities
These may be files, database queries, or anything that can be referred to by a URI
Can even include non-XML content

XML Applications

A specific markup language that uses the XML meta-syntax is called an XML application
Different XML applications have their own more constricted syntaxes and vocabularies within the broader XML syntax
Further syntax can be layered on top of this; e.g. data typing through schemas

Example XML Applications

Web Pages
Mathematical Equations
Music Notation
Vector Graphics
Metadata
and more...

Mathematical Markup Language

<?xml version="1.0"?>
<html xmlns="http://www.w3.org/TR/REC-html40"
      xmlns:m="http://www.w3.org/TR/REC-MathML/"
>
<head>
<title>Fiat Lux</title>
<meta name="GENERATOR" content="amaya V1.3b" />
</head>
<body>

<P>
And God said,
</P>

<math>
  <m:mrow>
    <m:msub>
      <m:mi>&delta;</m:mi>
      <m:mi>&alpha;</m:mi>
    </m:msub>
    <m:msup>
      <m:mi>F</m:mi>
      <m:mi>&alpha;&beta;</m:mi>
    </m:msup>
    <m:mi></m:mi>
    <m:mo>=</m:mo>
    <m:mi></m:mi>
    <m:mfrac>
      <m:mrow>
        <m:mn>4</m:mn>
        <m:mi>&pi;</m:mi>
      </m:mrow>
      <m:mi>c</m:mi>
    </m:mfrac>
    <m:mi></m:mi>
    <m:msup>
      <m:mi>J</m:mi>
      <m:mrow>
        <m:mi>&beta;</m:mi>
        <m:mo></m:mo>
      </m:mrow>
    </m:msup>
  </m:mrow>
</math>

<P>
and there was light
</P>
</body>
</html>

Channel Definition Format

<?xml version="1.0"?>
<CHANNEL HREF="http://www.ibiblio.org/xml/index.html">
  <TITLE>Cafe con Leche</TITLE>
  <ITEM HREF="http://www.ibiblio.org/xml/books.html">
    <TITLE>Books about XML</TITLE>
  </ITEM>
  <ITEM HREF="http://www.ibiblio.org/xml/tradeshows.html">
    <TITLE>Trade shows and conferences about XML</TITLE>
  </ITEM>
  <ITEM HREF="http://www.ibiblio.org/xml/lists.htm">
    <TITLE>Mailing Lists dedicated to XML</TITLE>
  </ITEM>
</CHANNEL>

Classic Literature

Vector Graphics

Vector Markup Language (VML)

Internet Explorer 5.0, 5.5
Microsoft Office 2000

Scalable Vector Graphics (SVG)

A VML document

The Resource Description Framework (RDF)

Meta-data
Dublin Core
Better Web searching

An Example of RDF

<rdf:RDF 
 xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
  xmlns:dc="http://purl.org/DC/>
  <rdf:Description about="http://www.ibiblio.org/xml/>
    <dc:CREATOR>Elliotte Rusty Harold</dc:CREATOR>
    <dc:TITLE>Cafe con Leche</dc:TITLE>
  </rdf:Description>
</rdf:RDF>

XML for XML

XSL: The Extensible Stylesheet Language
The W3C XML Schema Language
XLink: The Extensible Linking Language

XSL: The Extensible Stylesheet Language

Schemas

Data typing in XML is weak
DTDs use a strange non-XML syntax
Limited compatiblity with namespaces
Limited extensibility
Schemas fix all these problems
There are multiple schema languages including:
- Rick Jelliffe's Schematron
- Murato Makoto's RELAX
- James Clark's TreX
- The W3C XML Schema Language

W3C XML Schema Language Example

<?xml version="1.0"?>
<xsd:schema xmlns:xsd="http://www.w3.org/2000/10/XMLSchema">
 
  <xsd:element name="SONG" type="SongType"/>

  <xsd:complexType name="SongType">
    <xsd:seq>
      <xsd:element name="TITLE" type="xsd:string" 
                   minOccurs="1" maxOccurs="1"/>
      <xsd:element name="COMPOSER"  type="xsd:string" 
                   minOccurs="1" maxOccurs="unbounded"/>
      <xsd:element name="PRODUCER"  type="xsd:string" 
                   minOccurs="0" maxOccurs="unbounded"/>
      <xsd:element name="PUBLISHER" type="xsd:string" 
                   minOccurs="0" maxOccurs="1"/>
  
      <xsd:element name="LENGTH" type="xsd:timeDuration" 
                   minOccurs="0" maxOccurs="1"/>
      <xsd:element name="YEAR"   type="xsd:year" 
                   minOccurs="1" maxOccurs="1"/>

      <xsd:element name="ARTIST" type="xsd:string" 
                   minOccurs="1" maxOccurs="unbounded"/>
    </xsd:seq>
  </xsd:complexType>

</xsd:schema>

XLinks

Any element can be a link
Links can be bi-directional
Links can be separated from the documents they connect

<footnote xlink:type="simple" xlink:href="footnote7.xml">7</footnote>

File Formats, in-house applications, and other behind the scenes uses

Microsoft Office 2000
Netscape What's Related

Part III: A Practical Example

A larger example: Music Catalog

Examine the data
Design a vocabulary for the data
Write a style sheet

Sample Catalog

http://www.ibiblio.org/nywc/
Offline version/

Organizing the Data

XML documents are trees.
XML elements contain other elements as well as text
Within these limits there's more than one way to organize the data
- Hierarchically
- Relationally
- Objects

What is the Root Element

The catalog?
A custom Document element?

The Root Element

Choose catalog for the root element
Everything else will be a descendant of catalog
This is not the only possible choice

<?xml version="1.0" encoding="ISO-8859-1"?>
<catalog>
  Everything else will go here...
</catalog>

View in Browser

What are the Immediate Children of the Root?

Composers?
Songs/Compositions?
Categories?
All of the Above?

Child Elements

<?xml version="1.0" encoding="ISO-8859-1"?>
<catalog>

  <category>
    Small chamber ensembles - 2-4 Players by New York Women Composers
  </category>

</catalog>

View in Browser

White space in XML is not especially significant

<?xml version="1.0" encoding="ISO-8859-1"?>
<catalog><category>Small chamber ensembles 
- 2-4 Players by New York Women Composers</category></catalog>

View in Browser

Composers

Each composer has a name

<?xml version="1.0" encoding="ISO-8859-1"?>
<catalog>

  <category>
    Small chamber ensembles - 2-4 Players by New York Women Composers
  </category>

  <composer>
    <name>Julie Mandel</name>
  </composer>

  <composer>
    <name>Margaret De Wys</name>
  </composer>  
    
  <composer>
    <name>Beth Anderson</name>
  </composer>
    
  <composer>
    <name>Linda Bouchard</name>
  </composer>

</catalog>

View in Browser

Grand Children

It's better for sorting to divide names into first, middle, and last
Some (e.g. middle name) elements may be empty

<?xml version="1.0" encoding="ISO-8859-1"?>
<catalog>

  <category>
    Small chamber ensembles - 2-4 Players by New York Women Composers
  </category>

  <composer>
    <name>
      <first_name>Julie</first_name> 
      <middle_name></middle_name> 
      <last_name>Mandel</last_name>
    </name>
  </composer>

  <composer>
    <name>
      <first_name>Margaret</first_name> 
      <middle_name>De</middle_name> 
      <last_name>Wys</last_name>
    </name>
  </composer>  
    
  <composer>
    <name>
      <first_name>Beth</first_name> 
      <middle_name></middle_name> 
      <last_name>Anderson</last_name>
    </name>
  </composer>
    
  <composer>
    <name>
      <first_name>Linda</first_name> 
      <middle_name></middle_name> 
      <last_name>Bouchard</last_name>
    </name>
  </composer>

</catalog>

View in Browser

Attributes

Some people have the same names
Use an ID number to disambiguate
Store the ID number in an id attribute
name=value
An element may not have two attributes with the same name
Attribute values must be quoted

<?xml version="1.0" encoding="ISO-8859-1"?>
<catalog>

  <category>
    Small chamber ensembles - 2-4 Players by New York Women Composers
  </category>

  <composer id="c1">
    <name>
      <first_name>Julie</first_name> 
      <middle_name></middle_name> 
      <last_name>Mandel</last_name>
    </name>
  </composer>

  <composer id="c2">
    <name>
      <first_name>Margaret</first_name> 
      <middle_name>De</middle_name> 
      <last_name>Wys</last_name>
    </name>
  </composer>  
    
  <composer id="c3">
    <name>
      <first_name>Beth</first_name> 
      <middle_name></middle_name> 
      <last_name>Anderson</last_name>
    </name>
  </composer>
    
  <composer id="c4">
    <name>
      <first_name>Linda</first_name> 
      <middle_name></middle_name> 
      <last_name>Bouchard</last_name>
    </name>
  </composer>

</catalog>

View in Browser

Attributes vs. Elements

Attribute are for meta-data; elements are for data.
Does the reader want to see the information? If yes, use element content; if no, use attributes
Attributes are good for ID numbers, URLs, references, and other information not directly relevant to the reader

When not to use attributes

Attributes can't hold structure well.
Elements allow you to include meta-meta-data (information about the information about the information).
Not everyone always agrees on what is and isn't meta-data.
Elements are more extensible in the face of future changes.

Compositions

Let's look at an example of what we want:

Rendered HTML:

Brass Swale (1988) 5", tbn, 2 Bfl tpts, bar. hn: Tonal. Commissioned/Premiered by the Redlands' New Music Ensemble. (A swale is a meadow or a marsh where a lot of wild plants grow together. The composer discovered the word when a horse named Swale won the Kentucky Derby several years ago. Since her work is primarily collage of newly composed musical swatches, she has used the name extensively.) ACA - American Composers Alliance

Or in HTML:

<dt><cite>Brass Swale</cite> (1988) 5", tbn, 2 Bfl tpts, bar. hn</dt>
<dd><p>
Tonal. Commissioned/Premiered by the Redlands' New Music 
Ensemble. (A swale is a meadow or a marsh where a lot of 
wild plants grow together. The composer discovered the word 
when a horse named Swale won the Kentucky Derby several 
years ago. Since her work is primarily collage of newly 
composed musical swatches, she has used the name 
extensively.)  ACA - American Composers 
Alliance</p>
</dd>

Each composition has a

Title
Date
Description
List of instruments
Length
Publisher
Some pieces may be missing from some compositions

Composition Example in XML

  <composition>
    <title>Brass Swale</title>
    <date>1988</date> 
    <length>5"</length>
    <instruments>tbn, 2 Bfl tpts, bar, hn</instruments>
    <description>
      Tonal. Commissioned/Premiered by the Redlands' New Music
      Ensemble. (A swale is a meadow or a marsh where a lot of
      wild plants grow together. The composer discovered the word
      when a horse named Swale won the Kentucky Derby several
      years ago. Since her work is primarily collage of newly
      composed musical swatches, she has used the name
      extensively.)
    </description>
    <publisher>ACA - American Composers Alliance</publisher>
  </composition>

View in Browser

Further Divisions

  <composition>
    <title>Trio for Flute, Viola and Harp</title>
    <date><year>1994</year></date> 
    <length>13'38"</length>
    <instruments>fl, hp, vla</instruments>
    <description>
      <p>Premiered at Queens College in April, 1996 by Sue Ann Kahn, 
      Christine Ims, and Susan Jolles. In 3 movements :</p>
      <ul>
        <li>mvt. 1: 5:01</li>
        <li>mvt. 2: 4:11</li>
        <li>mvt. 3: 4:26</li>
      </ul>  
    </description>
    <publisher>Theodore Presser</publisher>
  </composition>

View in Browser

Attaching the Composer to the Composition

  <composition composer="c3">
    <title>Trio: Dream in D</title>
    <date><year>1980</year></date> 
    <length>10'</length>
    <instruments>fl, pn, vc, or vn, pn, vc</instruments>
    <description>
      Rhapsodic. Passionate. Available on CD 
      <cite><a href=
       "http://www.amazon.com/exec/obidos/ASIN/B000007NMH/qid=913265342/sr%3D1-2/">
       Two by Three
      </a></cite> from North/South Consonance (1998).
    </description> 
    <publisher></publisher>
  </composition>

View in Browser

Some Keywords For the Search Engines

<?xml version="1.0" encoding="ISO-8859-1"?>
<catalog>

  <category>
    Small chamber ensembles - 2-4 Players by New York Women Composers
  </category>

  <cataloging_info>
    <abstract>Compositions by the members of New York Women Composers</abstract>
    <keyword>music publishing</keyword>
    <keyword>scores</keyword>
    <keyword>women composers</keyword>
    <keyword>New York</keyword>
  </cataloging_info>

  <composer id="c1">
    <name>
      <first_name>Julie</first_name> 
      <middle_name></middle_name> 
      <last_name>Mandel</last_name>
    </name>
  </composer>
  
  ...
  
</catalog>

View in Browser

Standard Signature

Copyright notice
Name of maintainer
Email address of maintainer
Last modified date

<?xml version="1.0" encoding="ISO-8859-1"?>
<catalog>
...
  <last_updated>July 28, 1999</last_updated>
  <copyright>1999 New York Women Composers</copyright>
  <maintainer email="elharo@metalab.unc.edu" 
              url="http://www.macfaq.com/personal.html">
    <name>
      <first_name>Elliotte</first_name> 
      <middle_name>Rusty</middle_name> 
      <last_name>Harold</last_name>
    </name>
  </maintainer>

</catalog>

View in Browser

Cascading Style Sheets

A simple and straight-forward language for applying styles like bold and Helvetica to particular XML elements.
Rather than being stored as part of the document itself, all the style information is placed in a separate document called a style sheet.
Partially supported by Mozilla, Netscape 6, IE 5.0/5.5, and Opera 4.0/5.0
Full W3C Recommendation

A Blank Style Sheet

<?xml version="1.0" encoding="ISO-8859-1"?>
<?xml-stylesheet type="text/css" href="compositions1.css"?>
<catalog>
...
</catalog>

View in Browser

The Default Rule

Not every element needs a rule
The root element should be at least display: block

catalog { font-family: "New York", "Times New Roman", serif; 
          font-size: 14pt; 
          background-color: white; 
          color: black; 
          display: block }

View in Browser

A style rule for the category element

Make it look like an H1 heading

category { display: block; 
          font-family: Helvetica, Arial, sans;
          font-size: 32pt; 
          font-weight: bold; 
          text-align: center
         }
       
catalog { font-family: New York, Times New Roman, serif; 
          font-size: 14pt; 
          background-color: white; 
          color: black; 
          display: block 
        }

View in Browser

A style rule for the composer element

Make it look like a level 2 head
No need to stylize the first, middle, and last names separately

composer { display: block; 
          font-family: Helvetica, Arial, sans;
          font-size: 24pt; 
          font-weight: bold; 
          text-align: left
         }

View in Browser

A style rule for the title element

composition title { display: block; 
       font-family: Helvetica, Arial, sans;
       font-size: 18pt; 
       font-weight: bold; 
       text-align: left
      }

View in Browser

A style rule for the catalog info

// cataloging_info is only for search engines
cataloging_info { display: none;
       color: white}

display: none requires CSS2:

View in Browser

Style rules for the signature

  <last_updated>July 28, 1999</last_updated>
  <copyright>1999 New York Women Composers</copyright>
  <maintainer email="elharo@metalab.unc.edu" 
              url="http://www.macfaq.com/personal.html">
    <name>
      <first_name>Elliotte</first_name> 
      <middle_name>Rusty</middle_name> 
      <last_name>Harold</last_name>
    </name>
  </maintainer>

last_updated, copyright, maintainer {display: block;
       font-size: small}
       
copyright:before {content: "Copyright " }

last_updated:before {content: "Last Modified " }

last_updated {margin-top: 2ex }

Again, some of this requires CSS2

View in Browser

Style Rules for composition children

composition * {display:list-item}
       
description {display: block}

View in Browser

Finished Style Sheet

category { display: block; 
          font-family: Helvetica, Arial, sans;
          font-size: 32pt; 
          font-weight: bold; 
          text-align: center
         }
       
catalog { font-family: "New York", "Times New Roman", serif; 
          font-size: 14pt; 
          background-color: white; 
          color: black; 
          display: block
        }
      
composer { display: block; 
           font-family: Helvetica, Arial, sans;
           font-size: 24pt; 
           font-weight: bold; 
           text-align: left
         }  
       
composition title { display: block; 
       font-family: Helvetica, Arial, sans;
       font-size: 18pt; 
       font-weight: bold; 
       text-align: left}
       
composition * {display:list-item}
       
description {display: block}
              
// cataloging_info is only for search engines
cataloging_info { display: none;
       color: #FFFFFF}
       
last_updated, copyright, maintainer {display: block;
       font-size: small}
       
copyright:before {content: "Copyright " }

last_updated:before {content: "Last Modified " }

last_updated {margin-top: 2ex }

Possible Extensions

Should be able to match composers with compositions
Should be able to sort composers and compositions by name
Should be able to include data from attributes; e.g. the maintainer's email address
Horizontal rules would be nice
Better header (e.g. title and meta tags) would be nice

Possible Solutions

CSS Level 3?
XSL
XSL + JavaScript

CSS or XSL?

CSS has broader support
CSS is more stable
XSL is much more powerful
XSL can be used without browser support by transforming to HTML on the server side

Part IV: Well-formedness

Every XML document must be well-formed.
Parsers are not allowed to accept malformed XML documents.

Well-formedness Rules

Open and close all tags
Empty tags end with />
There is a unique root element
Elements may not overlap
Attribute values are quoted
< and & are only used to start tags and entities
Only the five predefined entity references are used
Plus more...

Open and close all tags

Good:
- <p>The quick brown fox jumped over the lazy dog</p>
- <li>A very <B>important</B> point</li>
- Copyright 1999 Elliotte Rusty Harold<br></br>
Bad:
- The quick brown fox jumped over the lazy dog<p>
- <li>A very <B>important point
- Copyright 1999 Elliotte Rusty Harold<br>

Empty tags end with />

<BR/>, <HR/>, and <IMG/> instead of <BR>, <HR>, and <IMG>
Web browsers deal inconsistently with these
Can use <BR></BR> <HR></HR> <IMG></IMG> instead
<BR CLASS="EMPTY"/> seems to work best.

There is a unique root element

One element completely contains all other elements of the document
This is HTML in HTML files
The XML declaration and xml-stylesheet processing instruction are not elements

Elements may not overlap

If an element contains a start tag for an element, it must also contain the corresponding end tag
Empty elements may appear anywhere
Every non root element has a parent element

Attribute values are quoted

Good:

<A HREF="http://www.ibiblio.org/xml/">
<DIV ALIGN="CENTER">
<A HREF="http://www.ibiblio.org/xml/">
<EMBED SRC="minnesotaswale.aif" hidden="hidden">

Bad:

<A HREF=http://www.ibiblio.org/xml/>
<DIV ALIGN=CENTER>
<EMBED SRC=minnesotaswale.aif hidden=hidden>
<EMBED SRC="minnesotaswale.aif" hidden>

< and & are only used to start tags and entities

Good:
```
<H1>O'Reilly &amp; Associates</H1>
```
Bad:
```
<H1>O'Reilly & Associates</H1>
```

Good:

<CODE>for (int i = 0; i &lt;= args.length; i++ ) { </CODE>

Bad:

<CODE>for (int i = 0; i <= args.length; i++ ) { </CODE>

Only the five predefined entity references are used

Good:

&amp; 
&lt; 
&gt; 
&quot; 
&apos;

Bad:

&copy;
&reg;
&tm;
&alpha;
&eacute;
&nbsp;

etc.

Entity references must end with a semicolon.
- < is good
- &lt is bad

Character References

Decimal:

¡ ¡

¢ ¢

£ £

¤ ¤

¥ ¥

¦ ¦
Hexadecimal

¡ ¡

¢ ¢

£ £

¤ ¤

¥ ¥

¦ ¦

Part V: DTDs

Well-formedness vs validity

There are two levels of conformance to XML
Well-formed documents are correct with or without a DTD. They adhere to the basic syntax rules of XML
Valid documents also adhere to the constraints specified in a DTD
All valid documents are well-formed; not all well-formed document are valid.

DTDs and Validity

A Document Type Definition (DTD) describes the elements and attributes that may appear in a document
Validation compares a particular document against a DTD
Well-formedness is a prerequisite for validity

What is a DTD?

A DTD lists the elements, attributes, and entities contained in a document
A DTD defines the relationships between different elements and attributes

A DTD for songs:

<!ELEMENT SONG (TITLE, COMPOSER+, PRODUCER*, PUBLISHER*, 
                 LENGTH?, YEAR?, ARTIST+)>

<!ELEMENT TITLE (#PCDATA)>

<!ELEMENT COMPOSER (#PCDATA)>
<!ELEMENT PRODUCER (#PCDATA)>
<!ELEMENT PUBLISHER (#PCDATA)>
<!ELEMENT LENGTH (#PCDATA)>
<!-- This should be a four digit year like "1999",
     not a two-digit year like "99" -->
<!ELEMENT YEAR (#PCDATA)>

<!ELEMENT ARTIST (#PCDATA)>

Normally stored in a separate file

Validity

To be valid an XML document must be

Well-formed
Must have a document type declaration
Must comply with the constraints specified in the DTD

A Valid Song Document

<?xml version="1.0"?>
<!DOCTYPE SONG SYSTEM "song.dtd">
<SONG>
  <TITLE>Hot Cop</TITLE>
  <COMPOSER>Jacques Morali</COMPOSER>
  <COMPOSER>Henri Belolo</COMPOSER>
  <COMPOSER>Victor Willis</COMPOSER>
  <PRODUCER>Jacques Morali</PRODUCER>
  <PUBLISHER>PolyGram Records</PUBLISHER>
  <LENGTH>6:20</LENGTH>
  <YEAR>1978</YEAR>
  <ARTIST>Village People</ARTIST>
</SONG>

Checking Validity

To check validity you pass the document through a validating parser which should report any errors it finds. For example,

% java sax.SAXCount -v invalidhotcop.xml
Error at (file file:/D:/speaking/SD99EAST/dtds/invalidhotcop.xml, line 10, char
8): Element "<SONG>" is not valid because it does not follow the rule, "(TITLE,C
OMPOSER+,PRODUCER*,PUBLISHER*,LENGTH?,YEAR?,ARTIST+)".
invalidhotcop.xml: 281 ms

A valid document:

% java sax.SAXCount -v validhotcop.xml
validhotcop.xml: 170 ms

Internal DTDs

<?xml version="1.0"?>
<!DOCTYPE SONG [
  <!ELEMENT SONG (TITLE, COMPOSER+, PRODUCER*, PUBLISHER*, 
                  LENGTH?, YEAR?, ARTIST+)>

  <!ELEMENT TITLE (#PCDATA)>

  <!ELEMENT COMPOSER (#PCDATA)>
  <!ELEMENT PRODUCER (#PCDATA)>
  <!ELEMENT PUBLISHER (#PCDATA)>
  <!ELEMENT LENGTH (#PCDATA)>
  <!-- This should be a four digit year like "1999",
     not a two-digit year like "99" -->
  <!ELEMENT YEAR (#PCDATA)>

  <!ELEMENT ARTIST (#PCDATA)>
]>
<SONG>
  <TITLE>Hot Cop</TITLE>
  <COMPOSER>Jacques Morali</COMPOSER>
  <COMPOSER>Henri Belolo</COMPOSER>
  <COMPOSER>Victor Willis</COMPOSER>
  <PRODUCER>Jacques Morali</PRODUCER>
  <PUBLISHER>PolyGram Records</PUBLISHER>
  <LENGTH>6:20</LENGTH>
  <YEAR>1978</YEAR>
  <ARTIST>Village People</ARTIST>
</SONG>

The importance of validation

Ensures that data is correct before feeding it into a program
Ensures that a format is followed
Establishes what must be supported
Not all documents need to be valid; sometimes well-formed is enough

Where are DTDs Important?

Domain-Specific Markup Languages
Self-Describing Data
Interchange of Data Among Applications
Structured and Integrated Data

Domain-Specific Markup Languages

A DTD precisely describes the format
DTDs verify that documents adhere to the format
Ensures interoperability of unrelated tools

Self-Describing Data

DTDs explain the format so reverse engineering isn't as necessary
Comments in DTDs can go even further

<!-- This should be a four digit year like "1999",
     not a two-digit year like "99" -->
<!ELEMENT YEAR (#PCDATA)>

Interchange of Data Among Applications

E-commerce and syndication
DTDs make sure that two independent applications speak the same language
DTDs detect malformed data
DTDs verify correct data

Structured and Integrated Data

Can specify relationships between elements using element declarations
Can assemble data from multiple sources using external entity references declared in the DTD

An Example Document

<?xml version="1.0" encoding="ISO-8859-1"?>
<catalog>

  <category>
    Small chamber ensembles - 2-4 Players by New York Women Composers
  </category>

  <cataloging_info>
    <abstract>Compositions by the members of New York Women Composers</abstract>
    <keyword>music publishing</keyword>
    <keyword>scores</keyword>
    <keyword>women composers</keyword>
    <keyword>New York</keyword>
  </cataloging_info>

  <last_updated>July 28, 1999</last_updated>
  <copyright>1999 New York Women Composers</copyright>
  <maintainer email="elharo@metalab.unc.edu" 
              url="http://www.macfaq.com/personal.html">
    <name>
      <first_name>Elliotte</first_name> 
      <middle_name>Rusty</middle_name> 
      <last_name>Harold</last_name>
    </name>
  </maintainer>

  <composer id="c1">
    <name>
      <first_name>Julie</first_name> 
      <middle_name></middle_name> 
      <last_name>Mandel</last_name>
    </name>
  </composer>

  <composer id="c2">
    <name>
      <first_name>Margaret</first_name> 
      <middle_name>De</middle_name> 
      <last_name>Wys</last_name>
    </name>
  </composer>  
    
  <composer id="c3">
    <name>
      <first_name>Beth</first_name> 
      <middle_name></middle_name> 
      <last_name>Anderson</last_name>
    </name>
  </composer>
    
  <composer id="c4">
    <name>
      <first_name>Linda</first_name> 
      <middle_name></middle_name> 
      <last_name>Bouchard</last_name>
    </name>
  </composer>
    
  <composition composer="c1">
    <title>Trio for Flute, Viola and Harp</title>
    <date><year>(1994)</year></date> 
    <length>13'38"</length>
    <instruments>fl, hp, vla</instruments>
    <description>
      <p>Premiered at Queens College in April, 1996 by Sue Ann Kahn, 
      Christine Ims, and Susan Jolles. In 3 movements :</p>
      <ul>
        <li>mvt. 1: 5:01</li>
        <li>mvt. 2: 4:11</li>
        <li>mvt. 3: 4:26</li>
      </ul>  
    </description>
    <publisher>Theodore Presser</publisher>
  </composition>

  <composition composer="c2">
    <title>Charmonium</title>
    <date><year>(1991)</year></date> 
    <length>9'</length>
    <instruments>2 vln, vla, vc</instruments>
    <description>
      Commissioned as quartet for the Meridian String Quartet. 
      Sonorous, bold. Moderate difficulty. Tape available.
    </description> 
    <publisher></publisher>
  </composition>

  <composition composer="c1">
    <title>Invention for Flute and Piano</title>
    <date><year>(1994)</year></date> 
    <length></length>
    <instruments>fl, pn</instruments>
    <description>3 movements</description> 
    <publisher></publisher>
  </composition>

  <composition composer="c3">
    <title>Little Trio</title>
    <date><year>(1984)</year></date> 
    <length>4'</length>
    <instruments>fl, guit, va</instruments>
    <description></description> 
    <publisher>ACA</publisher>
  </composition>

  <composition composer="c3">
    <title>Dr. Blood's Mermaid Lullaby</title>
    <date><year>(1980)</year></date> 
    <length>3'</length>
    <instruments>fl or ob, or vn, or vc, pn</instruments>
    <description></description> 
    <publisher>ACA</publisher>
  </composition>

  <composition composer="c3">
    <title>Trio: Dream in D</title>
    <date><year>(1980)</year></date> 
    <length>10'</length>
    <instruments>fl, pn, vc, or vn, pn, vc</instruments>
    <description>
      Rhapsodic. Passionate. Available on CD 
      <cite><a href="http://www.amazon.com/exec/obidos/ASIN/B000007NMH/qid%3D913265342/sr%3D1-2/">Two by Three</a></cite> 
      from North/South Consonance (1998).
    </description> 
    <publisher></publisher>
  </composition>

  <composition composer="c4">
    <title>Propos II</title>
    <date><year>(1985)</year></date> 
    <length>11'</length>
    <instruments>2 tpt</instruments>
    <description>Arrangement from Propos</description> 
    <publisher></publisher>
  </composition>

  <composition composer="c4">
    <title>Rictus En Mirroir</title>
    <date><year>(1985)</year></date> 
    <length>14'</length>
    <instruments>fl, ob, hpschd, vc</instruments>
    <description></description> 
    <publisher></publisher>
  </composition>

</catalog>

View in Browser

Element Declarations

Each tag must be declared in a <!ELEMENT> declaration.
A <!ELEMENT> declaration gives the name and content model of the element
The content model uses a simple regular expression-like grammar to precisely specify what is and isn't allowed in an element

Content Specifications

ANY
#PCDATA
Sequences
Choices
Mixed Content
Modifiers
EMPTY

ANY

<!ELEMENT catalog ANY>

A catalog can contain any child element and/or raw text (parsed character data)

#PCDATA

Parsed Character Data; i.e. raw text, no markup. For example,

  <year>1984</year>

<!ELEMENT year (#PCDATA)>

#PCDATA

Valid:

<year>1999</year>
<year>99</year>
<year>1999 C.E.</year>
<year>
 The year of our Lord one thousand, nine hundred, and ninety-nine
</year>

Invalid:

<year>
<month>January</month>
<month>February</month>
<month>March</month>
<month>April</month>
<month>May</month>
<month>June</month>
<month>July</month>
<month>August</month>
<month>September</month>
<month>October</month>
<month>November</month>
<month>December</month>
</year>

#PCDATA

There are a number of elements in the example document that only contain PCDATA:

<!ELEMENT category (#PCDATA)>
<!ELEMENT abstract (#PCDATA)>
<!ELEMENT keyword (#PCDATA)>
<!ELEMENT last_updated (#PCDATA)>
<!ELEMENT copyright (#PCDATA)>
<!ELEMENT first_name (#PCDATA)>
<!ELEMENT middle_name (#PCDATA)>
<!ELEMENT last_name (#PCDATA)>
<!ELEMENT title (#PCDATA)>
<!ELEMENT year (#PCDATA)>
<!ELEMENT instruments (#PCDATA)>
<!ELEMENT publisher (#PCDATA)>
<!ELEMENT length (#PCDATA)>

Comments in DTDs

DTDs seem as obfuscated as C.
Comments can improve this by giving example elements
Comments are the same as in HTML; e.g.

<!-- e.g. "1999 New York Women Composers", 
     not "Copyright 1999 New York Women Composers" -->
<!ELEMENT copyright (#PCDATA)>

Child Elements

    <date><year>1994</year></date>

To declare that a date element must have a year child:

<!ELEMENT date (year)>

Child Elements

You only have to declare the immediate children

   <maintainer email="elharo@metalab.unc.edu" 
              url="http://www.macfaq.com/personal.html">
    <name>
      <first_name>Elliotte</first_name> 
      <middle_name>Rusty</middle_name> 
      <last_name>Harold</last_name>
    </name>
  </maintainer>

  <composer id="c1">
    <name>
      <first_name>Julie</first_name> 
      <middle_name></middle_name> 
      <last_name>Mandel</last_name>
    </name>
  </composer>

To declare that a maintainer element must have a name child:

<!ELEMENT maintainer (name)>
<!ELEMENT composer (name)>

Sequences

    <name>
      <first_name>Elliotte</first_name> 
      <middle_name>Rusty</middle_name> 
      <last_name>Harold</last_name>
    </name>

Separate multiple required child elements with commas; e.g.
```
<!ELEMENT name (first_name, middle_name, last_name)>
```
A list of child elements separated by commas is called a sequence

More Sequences

ELEMENT

The element being described must have only child elements, no mixed content
You must know the order of the child elements
You must know the type of each child element
You must know the number of child elements
The number can be relaxed with wild cards

One or More Children +

  <cataloging_info>
    <abstract>Compositions by the members of New York Women Composers</abstract>
    <keyword>music publishing</keyword>
    <keyword>scores</keyword>
    <keyword>women composers</keyword>
    <keyword>New York</keyword>
  </cataloging_info>

The + suffix indicates that one or more of that element is required at that point

<!ELEMENT cataloging_info (abstract, keyword+)>

Zero or More Children *

The * suffix indicates that zero, one, or more of that element is required at that point

<!ELEMENT catalog (category, cataloging_info, last_updated, copyright, 
                   maintainer, composer*, composition*)>

Zero or One Children ?

  <composition composer="c1">
    <title>Trio for Flute, Viola and Harp</title>
    <date><year>1994</year></date> 
    <length>13'38"</length>
    <instruments>fl, hp, vla</instruments>
    <description>
      <p>Premiered at Queens College in April, 1996 by Sue Ann Kahn, 
      Christine Ims, and Susan Jolles. In 3 movements :</p>
      <ul>
        <li>mvt. 1: 5:01</li>
        <li>mvt. 2: 4:11</li>
        <li>mvt. 3: 4:26</li>
      </ul>  
    </description>
    <publisher>Theodore Presser</publisher>
  </composition>

Suffixing an element name with a question mark (?) in the content model indicates that either 0 or 1 (but not more than one) of that element are expected at that position

<!ELEMENT composition 
   (title, date, length?, instruments, description?, publisher?)>

Choices

A choice indicates one element or another but not both
A choice is signified by a vertical bar |
There can be two or more elements in a choice

<!ELEMENT date (year | ISODate)>
<!ELEMENT year (#PCDATA)>
<!ELEMENT ISODate (#PCDATA)>

Mixed Content

<!ELEMENT description (#PCDATA | ul | a | cite | p)*>
<!ELEMENT cite (#PCDATA | a)*>
<!ELEMENT ul (li*)>
<!ELEMENT li (#PCDATA)>
<!ELEMENT a (#PCDATA)>
<!ELEMENT p (#PCDATA)>

Mixed content is both #PCDATA and child elements in a choice, followed by an asterisk
Should be avoided where possible
This is the only way to combine PCDATA with child elements in a content model
- #PCDATA must come first
- #PCDATA cannot be used in a sequence

Content Models You Can't Declare

Mixed content with other content models
Exactly one element of a given type but in any position (The SGML & operator)
Between M and N of a given element
Restrictions on the PCDATA; e.g. that the year element must contain a four-digit year

Attribute Declarations

Recall this element:

  <maintainer email="elharo@metalab.unc.edu" 
              url="http://www.macfaq.com/personal.html">
    <name>
      <first_name>Elliotte</first_name> 
      <middle_name>Rusty</middle_name> 
      <last_name>Harold</last_name>
    </name>
  </maintainer>

It is declared like this:

<!ELEMENT maintainer (name)>
<!ATTLIST maintainer email CDATA "webmaster@nywc.org">
<!ATTLIST maintainer url CDATA "http://www.ibiblio.org/nywc">

The general format of an <!ATTLIST> declaration is:

<!ATTLIST Element_name Attribute_name Type Default_value>

Multiple Attribute Declarations

  <maintainer email="elharo@metalab.unc.edu" 
              url="http://www.macfaq.com/personal.html">
    <name>
      <first_name>Elliotte</first_name> 
      <middle_name>Rusty</middle_name> 
      <last_name>Harold</last_name>
    </name>
  </maintainer>

It is declared like this:

<!ELEMENT maintainer (name)>
<!ATTLIST maintainer email CDATA "webmaster@nywc.org">
<!ATTLIST maintainer url CDATA "http://www.ibiblio.org/nywc">

But it can also be declared in a single <!ATTLIST> declaration like this:

<!ATTLIST maintainer email CDATA "webmaster@nywc.org" url CDATA "http://www.ibiblio.org/nywc/">

This is more obvious with better indentation:

<!ATTLIST maintainer email CDATA "webmaster@nywc.org" 
                     url   CDATA "http://www.ibiblio.org/nywc/">

Attribute Default Values

A literal string value
One of these three keywords

#REQUIRED
#IMPLIED
#FIXED

#REQUIRED

No default value is provided in the DTD
Document authors must provide an attribute value for each element

<!ELEMENT maintainer (name)>
<!ATTLIST maintainer email CDATA #REQUIRED 
                     url   CDATA #REQUIRED>

#IMPLIED

<!ELEMENT a (#PCDATA)>
<!ATTLIST a href CDATA #IMPLIED>

No default value in the DTD
Author may (but does not have to) provide a value with each element

#FIXED

Value is the same for all elements
Default value must be provided in DTD
Document author may not change default value

<!ELEMENT maintainer (name)>
<!ATTLIST maintainer email CDATA #FIXED "webmaster@nywc.org" 
                     url   CDATA #REQUIRED>

Attribute Types

CDATA
ID
IDREF
IDREFS
ENTITY
ENTITIES
NOTATION
NMTOKEN
NMTOKENS
Enumerated

CDATA

Most general attribute type
Value can be any string of text not containing a raw less-than sign (<) or quotation marks (")

<!ATTLIST maintainer email CDATA #REQUIRED 
                     url   CDATA #IMPLIED>

ID

Value must be an XML name
- May include letters, digits, underscores, hyphens, and periods
- May not include whitespace
- May or may not have the name "id" or "ID"
- May contain colons only if used for namespaces
Value must be unique within ID type attributes in the document
Generally the default value is #REQUIRED

<!ELEMENT composer (name)>
<!ATTLIST composer id ID #REQUIRED>

IDREF

Value matches the ID of an element in the same document
Used for links and the like
Multiple elements may share the same IDREF values

<!ELEMENT composition (title, date, length?, 
   instruments, description?, publisher?)>
<!ATTLIST composition composer IDREF #REQUIRED>

IDREFS

A list of ID values in the same document
Separated by white space

<!ELEMENT composition (title, date, length?, 
   instruments, description?, publisher?)>
<!ATTLIST composition composer IDREFS #REQUIRED>

Finished DTD

<!ELEMENT category (#PCDATA)>
<!ELEMENT abstract (#PCDATA)>
<!ELEMENT keyword (#PCDATA)>
<!ELEMENT last_updated (#PCDATA)>
<!ELEMENT copyright (#PCDATA)>
<!ELEMENT title (#PCDATA)>
<!ELEMENT instruments (#PCDATA)>
<!ELEMENT publisher (#PCDATA)>
<!ELEMENT length (#PCDATA)>

<!ELEMENT date (year | ISODate)>
<!ELEMENT year (#PCDATA)>
<!ELEMENT ISODate (#PCDATA)>

<!ELEMENT catalog (category, cataloging_info, last_updated, 
   copyright, maintainer, (composer | composition)*)>

<!ELEMENT cataloging_info (abstract, keyword+)>

<!ELEMENT description (#PCDATA | ul | a | cite | p)*>
<!ELEMENT cite (#PCDATA | a)*>
<!ELEMENT ul (li*)>
<!ELEMENT li (#PCDATA)>
<!ELEMENT a (#PCDATA)>
<!ELEMENT p (#PCDATA)>

<!ELEMENT maintainer (name)>
<!ELEMENT name (first_name, middle_name, last_name)>
<!ELEMENT first_name (#PCDATA)>
<!ELEMENT middle_name (#PCDATA)>
<!ELEMENT last_name (#PCDATA)>
<!ATTLIST maintainer email CDATA #REQUIRED 
                     url   CDATA #IMPLIED>
                     
<!ELEMENT composer (name)>
<!ATTLIST composer id ID #REQUIRED>

<!ELEMENT composition (title, date, length?, 
                          instruments, description?, publisher?)>
<!ATTLIST composition composer IDREFS #REQUIRED>

<!ATTLIST a href CDATA #REQUIRED>

Part VI: Namespaces

Raison d'etre

To distinguish between elements and attributes from different vocabularies with different meanings.
To group all related elements and attributes together so that a parser can easily recognize them.

The Need for Namespaces

The XLink specification defines an attribute with the name href. The XHTML specification also uses href attributes on some elements. And the XInclude specification uses href attributes.
An XSLT style sheet that will transform XHTML documents containing both Scalable Vector Graphics (SVG) pictures and MathML equations into XSL-Formatting object documents.
- The a, title, script, style and font elements in XHTML and SVG
- The table element in XHTML and XSL-FO
- The text element in XSLT and SVG
- The set element in MathML and SVG
An XSLT stylesheet that transforms a style sheet in an older version of the XSLT specification to a style sheet in a newer version of the XSLT specification.

Namespaces disambiguate elements

Namespaces disambiguate elements with the same name from each other by attaching different prefixes to names from different XML applications.
Each prefix is associated with a URI.
- Names whose prefixes are associated with the same URI are in the same namespace.
- Names whose prefixes are associated with different URIs are in different namespaces.

Namespace Syntax

Elements and attributes that are in namespaces have names that contain exactly one colon. They look like this:
```
rdf:description
xlink:type
xsl:template
```
Everything before the colon is called the prefix
Everything after the colon is called the local part.
The complete name including the colon is called the qualified name.

Namespace URIs

Each prefix in a qualified name is associated with a URI.
For example, all elements in XSLT 1.0 style sheets are associated with the http://www.w3.org/1999/XSL/Transform URI.
The customary prefix xsl is a shorthand for the longer URI http://www.w3.org/1999/XSL/Transform.
You can't use the URI in the element name directly.
{http://www.w3.org/1999/XSL/Transform}template

Binding Prefixes to Namespace URIs

Prefixes are bound to namespace URIs by attaching an xmlns:prefix attribute to the prefixed element or one of its ancestors.

<svg:svg xmlns:svg="http://www.w3.org/Graphics/SVG/SVG-19991203.dtd" 
 width="12cm" height="10cm">
  <svg:ellipse rx="110" ry="130" />
  <svg:rect x="4cm" y="1cm" width="3cm" height="6cm" />
</svg:svg>

Bindings have scope within the element where they're declared.
An SVG processor can recognize all three of these elements as SVG elements because they all have prefixes bound to the particular URI defined by the SVG specification.

Binding Prefixes to Namespace URIs Example

<xhtml:html xmlns:xhtml="http://www.w3.org/1999/xhtml"
            xmlns:xlink="http://www.w3.org/XML/XLink/0.9">
  <xhtml:head><xhtml:title>Three Namespaces</xhtml:title></xhtml:head>
  <xhtml:body>
    <xhtml:h1 align="center">An Ellipse and a Rectangle</xhtml:h1>
    <svg:svg xmlns:svg="http://www.w3.org/Graphics/SVG/SVG-19991203.dtd" 
             width="12cm" height="10cm">
      <svg:ellipse rx="110" ry="130" />
      <svg:rect x="4cm" y="1cm" width="3cm" height="6cm" />
    </svg:svg>
    <xhtml:p xlink:type="simple" 
      xlink:href="ellipses.html">
      More about ellipses
    </xhtml:p>
    <xhtml:p xlink:type="simple" xlink:href="rectangles.html">
      More about rectangles
    </xhtml:p>
    <xhtml:hr/>
    <xhtml:p>Last Modified February 13, 2000</xhtml:p>    
  </xhtml:body>
</xhtml:html>

Binding namespaces to prefixes with #FIXED ATTLIST declarations

<!ATTLIST svg:svg xmlns:svg (CDATA) #FIXED "http://www.w3.org/Graphics/SVG/SVG-19991203.dtd">

<svg:svg width="12cm" height="10cm">
  <svg:ellipse rx="110" ry="130" />
  <svg:rect x="4cm" y="1cm" width="3cm" height="6cm" />
</svg:svg>

Unprefixed attributes are never in any namespace

Unprefixed attributes are never in any namespace.
Being an attribute of an element in the http://www.w3.org/1999/xhtml namespace is not sufficient to put the attribute in the http://www.w3.org/1999/xhtml namespace.
The only way an attribute belongs to a namespace is if it has a declared prefix, like xlink:type and xlink:href.

URIs matter; not prefixes

Many XML applications have recommended prefixes. For example, SVG elements often use the prefix svg and Resource Description Framework (RDF) elements often have the prefix rdf. However, these prefixes are simply conventions, and can be changed based on necessity, convenience or whim.
Before a prefix can be used, it must be bound to a URI.
These URIs are standardized, not the prefixes.
The prefix can change as long as the URI stays the same.

Namespace URIs do not necessarily point to a document, page, or schema

Purely formal
Can point somewhere but do not have to
Parsers compare namespace URIs on a character by character basis. These are three different namespaces:
- http://www.w3.org/1999/XSL/Transform
- http://www.w3.org/1999/XSL/Transform/
- http://www.w3.org/1999/XSL/Transform/index.html

The Default Namespace

Indicate that an unprefixed element and all its unprefixed descendant elements belong to a particular namespace by attaching an xmlns attribute with no prefix:

<DATASCHEMA xmlns="http://www.w3.org/2000/P3Pv1">
  <DATA name="vehicle.make" type="text" short="Make" 
        category="preference" size="31"/>
  <DATA name="vehicle.model" type="text" short="Model" 
        category="preference" size="31"/>
  <DATA name="vehicle.year" type="number" short="Year" 
        category="preference" size="4"/>
  <DATA name="vehicle.license.state." type="postal." short="State" 
        category="preference" size="2"/>
  <DATA name="vehicle.license.number" type="text" 
        short="License Plate Number" category="preference" size="12"/>
</DATASCHEMA>

Both the DATASCHEMA and DATA elements are in the http://www.w3.org/2000/P3Pv1 namespace.
Default namespaces apply only to elements, not to attributes. Thus in the above example the name, type, short, category, and size attributes are not in any namespace.
You can change the default namespace within a particular element by adding an xmlns attribute to the element.

<html xmlns="http://www.w3.org/1999/xhtml"
      xmlns:xlink="http://www.w3.org/XML/XLink/0.9">
  <head><title>Three Namespaces</title></head>
  <body>
    <h1 align="center">An Ellipse and a Rectangle</h1>
    <svg xmlns="http://www.w3.org/Graphics/SVG/SVG-19991203.dtd" 
         width="12cm" height="10cm">
      <ellipse rx="110" ry="130" />
      <rect x="4cm" y="1cm" width="3cm" height="6cm" />
    </svg>
    <p xlink:type="simple" xlink:href="ellipses.html">
      More about ellipses
    </p>
    <p xlink:type="simple" xlink:href="rectangles.html">
      More about rectangles
    </p>
    <hr/>
    <p>Last Modified February 13, 2000</p>    
  </body>
</html>

Binding default namespaces to elements with #FIXED ATTLISTs

<!ATTLIST svg xmlns (CDATA) #FIXED "http://www.w3.org/Graphics/SVG/SVG-19991203.dtd">

<svg width="12cm" height="10cm">
  <ellipse rx="110" ry="130" />
  <rect x="4cm" y="1cm" width="3cm" height="6cm" />
</svg>

Namespaces and DTDs

DTDs must declare the qualified names
<!ELEMENT svg:text (#PCDATA)>
If the prefix changes, the DTD needs to change to.

Parameter entity references can help when the prefix changes or is removed:

<!ENTITY % mathml-colon               ''>
<!ENTITY % mathml-prefix              ''>

<!ENTITY % mathml-exp                 '%mathml-prefix;%mathml-colon;exp' >
<!ENTITY % mathml-abs                 '%mathml-prefix;%mathml-colon;abs' >
<!ENTITY % mathml-arg                 '%mathml-prefix;%mathml-colon;arg' >
<!ENTITY % mathml-real                '%mathml-prefix;%mathml-colon;real' >
<!ENTITY % mathml-imaginary           '%mathml-prefix;%mathml-colon;imaginary' >

To Learn More

This presentation: http://www.ibiblio.org/xml/slides/xmloneaustin2001/xml_fundamentals
XML in a Nutshell
- Elliotte Rusty Harold and W. Scott Means
- O'Reilly & Associates, 2001
- ISBN 0-596-00058-8
- XPath: http://www.oreilly.com/catalog/xmlnut/chapter/ch09.html
XML Bible, second edition
- Elliotte Rusty Harold
- Hungry Minds, 2001
- ISBN 0-7645-4760-7
- XLinks: http://www.ibiblio.org/xml/books/bible/updates/16.html
- XPointers: http://www.ibiblio.org/xml/books/bible/updates/17.html

Part VII: XSL, the Extensible Stylesheet Language

What Is XSL?

A transformation language (XSLT)
A formatting language (XSL-FO)

Versions

This talk covers:

XSL Transformations: November 16 1.0 Specification
XPath: November 16 1.0 Specification

The Process of an XSL Transformation

Something reads an XML document and forms a tree
The tree is passed to the XSLT Processor
The XSLT processor compares the nodes in the tree to the instructions in the style sheet
When the XSLT processor finds a match it outputs a tree fragment
(Optional) The complete output tree is serialized to some other format such as text, HTML, or an XML file

An Example XML Document

<?xml version="1.0" encoding="ISO-8859-1"?>
<catalog>

  <category>
    Small chamber ensembles - 2-4 Players by New York Women Composers
  </category>

  <cataloging_info>
    <abstract>Compositions by the members of New York Women Composers</abstract>
    <keyword>music publishing</keyword>
    <keyword>scores</keyword>
    <keyword>women composers</keyword>
    <keyword>New York</keyword>
  </cataloging_info>

  <last_updated>July 28, 1999</last_updated>
  <copyright>1999 New York Women Composers</copyright>
  <maintainer email="elharo@metalab.unc.edu" 
              url="http://www.macfaq.com/personal.html">
    <name>
      <first_name>Elliotte</first_name> 
      <middle_name>Rusty</middle_name> 
      <last_name>Harold</last_name>
    </name>
  </maintainer>

  <composer id="c1">
    <name>
      <first_name>Julie</first_name> 
      <middle_name></middle_name> 
      <last_name>Mandel</last_name>
    </name>
  </composer>

  <composer id="c2">
    <name>
      <first_name>Margaret</first_name> 
      <middle_name>De</middle_name> 
      <last_name>Wys</last_name>
    </name>
  </composer>  
    
  <composer id="c3">
    <name>
      <first_name>Beth</first_name> 
      <middle_name></middle_name> 
      <last_name>Anderson</last_name>
    </name>
  </composer>
    
  <composer id="c4">
    <name>
      <first_name>Linda</first_name> 
      <middle_name></middle_name> 
      <last_name>Bouchard</last_name>
    </name>
  </composer>
    
  <composition composer="c1">
    <title>Trio for Flute, Viola and Harp</title>
    <date><year>(1994)</year></date> 
    <length>13'38"</length>
    <instruments>fl, hp, vla</instruments>
    <description>
      <p>Premiered at Queens College in April, 1996 by Sue Ann Kahn, 
      Christine Ims, and Susan Jolles. In 3 movements :</p>
      <ul>
        <li>mvt. 1: 5:01</li>
        <li>mvt. 2: 4:11</li>
        <li>mvt. 3: 4:26</li>
      </ul>  
    </description>
    <publisher>Theodore Presser</publisher>
  </composition>

  <composition composer="c2">
    <title>Charmonium</title>
    <date><year>(1991)</year></date> 
    <length>9'</length>
    <instruments>2 vln, vla, vc</instruments>
    <description>
      Commissioned as quartet for the Meridian String Quartet. 
      Sonorous, bold. Moderate difficulty. Tape available.
    </description> 
    <publisher></publisher>
  </composition>

  <composition composer="c1">
    <title>Invention for Flute and Piano</title>
    <date><year>(1994)</year></date> 
    <length></length>
    <instruments>fl, pn</instruments>
    <description>3 movements</description> 
    <publisher></publisher>
  </composition>

  <composition composer="c3">
    <title>Little Trio</title>
    <date><year>(1984)</year></date> 
    <length>4'</length>
    <instruments>fl, guit, va</instruments>
    <description></description> 
    <publisher>ACA</publisher>
  </composition>

  <composition composer="c3">
    <title>Dr. Blood's Mermaid Lullaby</title>
    <date><year>(1980)</year></date> 
    <length>3'</length>
    <instruments>fl or ob, or vn, or vc, pn</instruments>
    <description></description> 
    <publisher>ACA</publisher>
  </composition>

  <composition composer="c3">
    <title>Trio: Dream in D</title>
    <date><year>(1980)</year></date> 
    <length>10'</length>
    <instruments>fl, pn, vc, or vn, pn, vc</instruments>
    <description>
      Rhapsodic. Passionate. Available on CD 
      <cite><a href="http://www.amazon.com/exec/obidos/ASIN/B000007NMH/qid%3D913265342/sr%3D1-2/">Two by Three</a></cite> 
      from North/South Consonance (1998).
    </description> 
    <publisher></publisher>
  </composition>

  <composition composer="c4">
    <title>Propos II</title>
    <date><year>(1985)</year></date> 
    <length>11'</length>
    <instruments>2 tpt</instruments>
    <description>Arrangement from Propos</description> 
    <publisher></publisher>
  </composition>

  <composition composer="c4">
    <title>Rictus En Mirroir</title>
    <date><year>(1985)</year></date> 
    <length>14'</length>
    <instruments>fl, ob, hpschd, vc</instruments>
    <description></description> 
    <publisher></publisher>
  </composition>

</catalog>

An XSL Style Sheet

<?xml version="1.0"?>
<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">



</xsl:stylesheet>

Let's use xt to apply this stylesheet to compositions.xml.

Windows executable:

C:> xt compositions.xml sheet1.xsl

Java executable:

C:> java -Dcom.jclark.xsl.sax.parser=com.jclark.xml.sax.CommentDriver
com.jclark.xsl.sax.Driver compositions.xml sheet1.xsl output1.html

Output

<?xml version="1.0" encoding="utf-8"?>

  
    Small chamber ensembles - 2-4 Players by New York Women Composers
  

  
    Compositions by the members of New York Women Composers
    music publishing
    scores
    women composers
    New York
  

  July 28, 1999
  1999 New York Women Composers
  
    
      Elliotte 
      Rusty 
      Harold
    
  

  
    
      Julie 
       
      Mandel
    
  

  
    
      Margaret 
      De 
      Wys
    
    
    
  
    
      Beth 
       
      Anderson
    
  
    
  
    
      Linda 
       
      Bouchard
    
  
    
  
    Trio for Flute, Viola and Harp
    1994 
    13'38"
    fl, hp, vla
    
      Premiered at Queens College in April, 1996 by Sue Ann Kahn, 
      Christine Ims, and Susan Jolles. In 3 movements :
      
        mvt. 1: 5:01
        mvt. 2: 4:11
        mvt. 3: 4:26
        
    
    Theodore Presser
  

  
    Charmonium
    1991 
    9'
    2 vln, vla, vc
    
      Commissioned as quartet for the Meridian String Quartet. 
      Sonorous, bold. Moderate difficulty. Tape available.
     
  

  
    Invention for Flute and Piano
    1994 
    fl, pn
    3 movements 
  

  
    Little Trio
    1984 
    4'
    fl, guit, va
    ACA
  

  
    Dr. Blood's Mermaid Lullaby
    1980 
    3'
    fl or ob, or vn, or vc, pn
    ACA
  

  
    Trio: Dream in D
    1980 
    10'
    fl, pn, vc, or vn, pn, vc
    
      Rhapsodic. Passionate. Available on CD 
      
      
      Two by Three 
      from North/South Consonance (1998).
     
  

  
    Propos II
    1985 
    11'
    2 tpt
    Arrangement from Propos 
  

  
    Rictus En Mirroir
    1985 
    14'
    fl, ob, hpschd, vc

View in browser

Templates

<?xml version="1.0"?>
<xsl:stylesheet version="1.0" 
                xmlns:xsl="http://www.w3.org/1999/XSL/Transform">

  <xsl:template match="composition">
    <h3><xsl:value-of select="title"/></h3>
  </xsl:template>

</xsl:stylesheet>

View Transformed Document in browser

The actual HTML output

<?xml version="1.0" encoding="utf-8"?>

  
    Small chamber ensembles - 2-4 Players by New York Women Composers
  

  
    Compositions by the members of New York Women Composers
    music publishing
    scores
    women composers
    New York
  

  July 28, 1999
  1999 New York Women Composers
  
    
      Elliotte 
      Rusty 
      Harold
    
  

  
    
      Julie 
       
      Mandel
    
  

  
    
      Margaret 
      De 
      Wys
    
    
    
  
    
      Beth 
       
      Anderson
    
  
    
  
    
      Linda 
       
      Bouchard
    
  
    
  <h3>Trio for Flute, Viola and Harp</h3>

  <h3>Charmonium</h3>

  <h3>Invention for Flute and Piano</h3>

  <h3>Little Trio</h3>

  <h3>Dr. Blood's Mermaid Lullaby</h3>

  <h3>Trio: Dream in D</h3>

  <h3>Propos II</h3>

  <h3>Rictus En Mirroir</h3>

Adding the root

<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet version="1.0" 
                xmlns:xsl="http://www.w3.org/1999/XSL/Transform">

  <xsl:template match="/">
    <html>
      <body>        
        
      </body>
    </html>
  </xsl:template>

  <xsl:template match="composition">
    <h3><xsl:value-of select="title"/></h3>
  </xsl:template>

</xsl:stylesheet>

View Transformed Document in browser

The actual HTML output

<html>
   <body></body>
</html>

Applying Templates

<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet version="1.0" 
                xmlns:xsl="http://www.w3.org/1999/XSL/Transform">

  <xsl:template match="/">
    <html>
      <body>
        <xsl:apply-templates/>
      </body>
    </html>
  </xsl:template>

  <xsl:template match="composition">
    <h3><xsl:value-of select="title"/></h3>
  </xsl:template>

</xsl:stylesheet>

View Transformed Document in browser

The actual HTML output

<html>
   <body>
      
      
      Small chamber ensembles - 2-4 Players by New York Women Composers
      
      
      
      Compositions by the members of New York Women Composers
      music publishing
      scores
      women composers
      New York
      
      
      July 28, 1999
      1999 New York Women Composers
      
      
      Elliotte 
      Rusty 
      Harold
      
      
      
      
      
      Julie 
       
      Mandel
      
      
      
      
      
      Margaret 
      De 
      Wys
      
        
      
      
      
      Beth 
       
      Anderson
      
      
      
      
      
      Linda 
       
      Bouchard
      
      
      
      
      <h3>Trio for Flute, Viola and Harp</h3>
      
      
      <h3>Charmonium</h3>
      
      
      <h3>Invention for Flute and Piano</h3>
      
      
      <h3>Little Trio</h3>
      
      
      <h3>Dr. Blood's Mermaid Lullaby</h3>
      
      
      <h3>Trio: Dream in D</h3>
      
      
      <h3>Propos II</h3>
      
      
      <h3>Rictus En Mirroir</h3>
      
      
   </body>
</html>

The select attribute

<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet version="1.0" 
                xmlns:xsl="http://www.w3.org/1999/XSL/Transform">

  <xsl:template match="/">
    <html>
       <xsl:apply-templates select="catalog"/>
    </html>
  </xsl:template>

  <xsl:template match="catalog">
    <head>
       <title><xsl:value-of select="category"/></title>      
    </head>
    <body>
       <h1><xsl:value-of select="category"/></h1>      
       <xsl:apply-templates select="composition"/>
    </body>
  </xsl:template>

  <xsl:template match="composition">
    <h3><xsl:value-of select="title"/></h3>
  </xsl:template>

</xsl:stylesheet>

View Transformed Document in browser

The actual HTML output

<html>
   <head>
      <meta http-equiv="Content-Type" content="application/xml; charset=utf-8">
   
      <title>
         Small chamber ensembles - 2-4 Players by New York Women Composers
         
      </title>
   </head>
   <body>
      <h1>
         Small chamber ensembles - 2-4 Players by New York Women Composers
         
      </h1>
      <h3>Trio for Flute, Viola and Harp</h3>
      <h3>Charmonium</h3>
      <h3>Invention for Flute and Piano</h3>
      <h3>Little Trio</h3>
      <h3>Dr. Blood's Mermaid Lullaby</h3>
      <h3>Trio: Dream in D</h3>
      <h3>Propos II</h3>
      <h3>Rictus En Mirroir</h3>
   </body>
</html>

Expanding the coverage

<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet version="1.0" 
                xmlns:xsl="http://www.w3.org/1999/XSL/Transform">

  <xsl:template match="/">
    <html>
       <xsl:apply-templates select="catalog"/>
    </html>
  </xsl:template>

  <xsl:template match="catalog">
    <head>
       <title><xsl:value-of select="category"/></title>      
    </head>
    <body>
       <h1><xsl:value-of select="category"/></h1>      
       <xsl:apply-templates select="composition"/>
       <hr/>
       Copyright <xsl:value-of select="copyright"/><br/>
       Last Modified: <xsl:value-of select="last_updated"/>
    </body>
  </xsl:template>

  <xsl:template match="composition">
    <h3><xsl:value-of select="title"/></h3>

    <ul>
     <li><xsl:value-of select="date"/></li>
     <li><xsl:value-of select="length"/></li>
     <li><xsl:value-of select="instruments"/></li>
     <li><xsl:value-of select="publisher"/></li>    
    </ul>

    <p><xsl:value-of select="description"/></p>    
    
  </xsl:template>

</xsl:stylesheet>

View Transformed Document in browser

The actual HTML output

<html>
   <head>
      <meta http-equiv="Content-Type" content="application/xml; charset=utf-8">
   
      <title>
         Small chamber ensembles - 2-4 Players by New York Women Composers
         
      </title>
   </head>
   <body>
      <h1>
         Small chamber ensembles - 2-4 Players by New York Women Composers
         
      </h1>
      <h3>Trio for Flute, Viola and Harp</h3>
      <ul>
         <li>1994</li>
         <li>13'38"</li>
         <li>fl, hp, vla</li>
         <li>Theodore Presser</li>
      </ul>
      <p>
         Premiered at Queens College in April, 1996 by Sue Ann Kahn, 
         Christine Ims, and Susan Jolles. In 3 movements :
         
         mvt. 1: 5:01
         mvt. 2: 4:11
         mvt. 3: 4:26
         
         
      </p>
      <h3>Charmonium</h3>
      <ul>
         <li>1991</li>
         <li>9'</li>
         <li>2 vln, vla, vc</li>
         <li></li>
      </ul>
      <p>
         Commissioned as quartet for the Meridian String Quartet. 
         Sonorous, bold. Moderate difficulty. Tape available.
         
      </p>
      <h3>Invention for Flute and Piano</h3>
      <ul>
         <li>1994</li>
         <li></li>
         <li>fl, pn</li>
         <li></li>
      </ul>
      <p>3 movements</p>
      <h3>Little Trio</h3>
      <ul>
         <li>1984</li>
         <li>4'</li>
         <li>fl, guit, va</li>
         <li>ACA</li>
      </ul>
      <p></p>
      <h3>Dr. Blood's Mermaid Lullaby</h3>
      <ul>
         <li>1980</li>
         <li>3'</li>
         <li>fl or ob, or vn, or vc, pn</li>
         <li>ACA</li>
      </ul>
      <p></p>
      <h3>Trio: Dream in D</h3>
      <ul>
         <li>1980</li>
         <li>10'</li>
         <li>fl, pn, vc, or vn, pn, vc</li>
         <li></li>
      </ul>
      <p>
         Rhapsodic. Passionate. Available on CD 
         
         
         Two by Three 
         from North/South Consonance (1998).
         
      </p>
      <h3>Propos II</h3>
      <ul>
         <li>1985</li>
         <li>11'</li>
         <li>2 tpt</li>
         <li></li>
      </ul>
      <p>Arrangement from Propos</p>
      <h3>Rictus En Mirroir</h3>
      <ul>
         <li>1985</li>
         <li>14'</li>
         <li>fl, ob, hpschd, vc</li>
         <li></li>
      </ul>
      <p></p>
      <hr>
      Copyright 1999 New York Women Composers<br>
      Last Modified: July 28, 1999
   </body>
</html>

Attributes

I want to add something like this to the footer so readers can contact me if there's a problem with the page:

Elliotte Rusty Harold<br/>
elharo@metalab.unc.edu

This information comes from the maintainer element:

  <maintainer email="elharo@metalab.unc.edu" 
              url="http://www.macfaq.com/personal.html">
    <name>
      <first_name>Elliotte</first_name> 
      <middle_name>Rusty</middle_name> 
      <last_name>Harold</last_name>
    </name>
  </maintainer>

So we need a way to get content from attributes in the input document. This is accomplished by prefixing the attribute name with @.

  <xsl:template match="catalog">
    <head>
       <title><xsl:value-of select="category"/></title>      
    </head>
    <body>
       <h1><xsl:value-of select="category"/></h1>      
       <xsl:apply-templates select="composition"/>
       <hr/>
       Copyright <xsl:value-of select="copyright"/><br/>
       Last Modified: <xsl:value-of select="last_updated"/><br/>
       <xsl:apply-templates select="maintainer"/>
    </body>
  </xsl:template>

  <xsl:template match="maintainer">
    <xsl:value-of select="name"/><br/>
    <xsl:value-of select="@email"/>
  </xsl:template>

View Transformed Document in browser

The actual HTML output

<html>
   <head>
      <meta http-equiv="Content-Type" content="application/xml; charset=utf-8">
   
      <title>
         Small chamber ensembles - 2-4 Players by New York Women Composers
         
      </title>
   </head>
   <body>
      <h1>
         Small chamber ensembles - 2-4 Players by New York Women Composers
         
      </h1>
      <h3>Trio for Flute, Viola and Harp</h3>
      <ul>
         <li>1994</li>
         <li>13'38"</li>
         <li>fl, hp, vla</li>
         <li>Theodore Presser</li>
      </ul>
      <p>
         Premiered at Queens College in April, 1996 by Sue Ann Kahn, 
         Christine Ims, and Susan Jolles. In 3 movements :
         
         mvt. 1: 5:01
         mvt. 2: 4:11
         mvt. 3: 4:26
         
         
      </p>
      <h3>Charmonium</h3>
      <ul>
         <li>1991</li>
         <li>9'</li>
         <li>2 vln, vla, vc</li>
         <li></li>
      </ul>
      <p>
         Commissioned as quartet for the Meridian String Quartet. 
         Sonorous, bold. Moderate difficulty. Tape available.
         
      </p>
      <h3>Invention for Flute and Piano</h3>
      <ul>
         <li>1994</li>
         <li></li>
         <li>fl, pn</li>
         <li></li>
      </ul>
      <p>3 movements</p>
      <h3>Little Trio</h3>
      <ul>
         <li>1984</li>
         <li>4'</li>
         <li>fl, guit, va</li>
         <li>ACA</li>
      </ul>
      <p></p>
      <h3>Dr. Blood's Mermaid Lullaby</h3>
      <ul>
         <li>1980</li>
         <li>3'</li>
         <li>fl or ob, or vn, or vc, pn</li>
         <li>ACA</li>
      </ul>
      <p></p>
      <h3>Trio: Dream in D</h3>
      <ul>
         <li>1980</li>
         <li>10'</li>
         <li>fl, pn, vc, or vn, pn, vc</li>
         <li></li>
      </ul>
      <p>
         Rhapsodic. Passionate. Available on CD 
         
         
         Two by Three 
         from North/South Consonance (1998).
         
      </p>
      <h3>Propos II</h3>
      <ul>
         <li>1985</li>
         <li>11'</li>
         <li>2 tpt</li>
         <li></li>
      </ul>
      <p>Arrangement from Propos</p>
      <h3>Rictus En Mirroir</h3>
      <ul>
         <li>1985</li>
         <li>14'</li>
         <li>fl, ob, hpschd, vc</li>
         <li></li>
      </ul>
      <p></p>
      <hr>
      Copyright 1999 New York Women Composers<br>
      Last Modified: July 28, 1999<br>
      Elliotte 
      Rusty 
      Harold
      <br>elharo@metalab.unc.edu
   </body>
</html>

Attribute Value Templates

It would be nice to make the maintainer's name a link to his home page, and his email address a mailto: link. In other words,we want to add this to the footer:

  <a href="http://www.macfaq.com/personal.html">Elliotte Rusty Harold</a><br/>
  <a href="mailto:elharo@metalab.unc.edu">elharo@metalab.unc.edu</a>

So we need a way to copy nodes from the input document to attribute values in the output document. This is done with an attribute value template

  <xsl:template match="maintainer">
    <a href="{@url}"><xsl:value-of select="name"/></a><br/>
    <a href="mailto:{@email}"><xsl:value-of select="@email"/></a>
  </xsl:template>

An attribute value template is a select expression inside curly braces such as {@url}. Here the attribute value template selects attribute values in the input document, but it can also select element content or more complicated expressions. Notice that the attribute value template does not have to be the only thing in the attribute value. There can even be more than one attribue value templates in an attribute value.

View Transformed Document in browser

The actual HTML output

<html>
   <head>
      <meta http-equiv="Content-Type" content="application/xml; charset=utf-8">
   
      <title>
         Small chamber ensembles - 2-4 Players by New York Women Composers
         
      </title>
   </head>
   <body>
      <h1>
         Small chamber ensembles - 2-4 Players by New York Women Composers
         
      </h1>
      <h3>Trio for Flute, Viola and Harp</h3>
      <ul>
         <li>1994</li>
         <li>13'38"</li>
         <li>fl, hp, vla</li>
         <li>Theodore Presser</li>
      </ul>
      <p>
         Premiered at Queens College in April, 1996 by Sue Ann Kahn, 
         Christine Ims, and Susan Jolles. In 3 movements :
         
         mvt. 1: 5:01
         mvt. 2: 4:11
         mvt. 3: 4:26
         
         
      </p>
      <h3>Charmonium</h3>
      <ul>
         <li>1991</li>
         <li>9'</li>
         <li>2 vln, vla, vc</li>
         <li></li>
      </ul>
      <p>
         Commissioned as quartet for the Meridian String Quartet. 
         Sonorous, bold. Moderate difficulty. Tape available.
         
      </p>
      <h3>Invention for Flute and Piano</h3>
      <ul>
         <li>1994</li>
         <li></li>
         <li>fl, pn</li>
         <li></li>
      </ul>
      <p>3 movements</p>
      <h3>Little Trio</h3>
      <ul>
         <li>1984</li>
         <li>4'</li>
         <li>fl, guit, va</li>
         <li>ACA</li>
      </ul>
      <p></p>
      <h3>Dr. Blood's Mermaid Lullaby</h3>
      <ul>
         <li>1980</li>
         <li>3'</li>
         <li>fl or ob, or vn, or vc, pn</li>
         <li>ACA</li>
      </ul>
      <p></p>
      <h3>Trio: Dream in D</h3>
      <ul>
         <li>1980</li>
         <li>10'</li>
         <li>fl, pn, vc, or vn, pn, vc</li>
         <li></li>
      </ul>
      <p>
         Rhapsodic. Passionate. Available on CD 
         
         
         Two by Three 
         from North/South Consonance (1998).
         
      </p>
      <h3>Propos II</h3>
      <ul>
         <li>1985</li>
         <li>11'</li>
         <li>2 tpt</li>
         <li></li>
      </ul>
      <p>Arrangement from Propos</p>
      <h3>Rictus En Mirroir</h3>
      <ul>
         <li>1985</li>
         <li>14'</li>
         <li>fl, ob, hpschd, vc</li>
         <li></li>
      </ul>
      <p></p>
      <hr>
      Copyright 1999 New York Women Composers<br>
      Last Modified: July 28, 1999<br><a href="http://www.macfaq.com/personal.html">
         Elliotte 
         Rusty 
         Harold
         
      </a><br><a href="mailto:elharo@metalab.unc.edu">elharo@metalab.unc.edu</a></body>
</html>

xsl:copy

Right now the descriptions in the output document are pure text. The descriptions in the input document are somewhat more styled and include paragraphs, unordered lists and citations; e.g.

    <description>
      <p>Premiered at Queens College in April, 1996 by Sue Ann Kahn, 
      Christine Ims, and Susan Jolles. In 3 movements :</p>
      <ul>
        <li>mvt. 1: 5:01</li>
        <li>mvt. 2: 4:11</li>
        <li>mvt. 3: 4:26</li>
      </ul>  
    </description>

But all this is stripped by the default template rule used for the description. We can use xsl:copy to move these elements into the output more or less as is. Here are the necessary rules for the four HTML elements found in compositions.xml:

  <xsl:template match="p">
    <xsl:copy>
      <xsl:apply-templates/>
    </xsl:copy>
  </xsl:template>  
  
  <!-- pass HTML along unchanged -->
  <xsl:template match="ul">
    <xsl:copy>
      <xsl:apply-templates/>
    </xsl:copy>
  </xsl:template>  
  
  <xsl:template match="li">
    <xsl:copy>
      <xsl:apply-templates"/>
    </xsl:copy>
  </xsl:template>  
  
  <xsl:template match="cite">
    <xsl:copy>
      <xsl:apply-templates"/>
    </xsl:copy>
  </xsl:template>

We also have to apply templates to the description element rather than taking its value:

  <xsl:template match="composition">
    <h3><xsl:value-of select="title"/></h3>

    <ul>
     <li><xsl:value-of select="date"/></li>
     <li><xsl:value-of select="length"/></li>
     <li><xsl:value-of select="instruments"/></li>
     <li><xsl:value-of select="publisher"/></li>    
    </ul>

    <p><xsl:apply-templates select="description"/></p>    
    
  </xsl:template>

View Transformed Document in browser

The generated HTML

<html>
   <head>
      <meta http-equiv="Content-Type" content="application/xml; charset=utf-8">
   
      <title>
         Small chamber ensembles - 2-4 Players by New York Women Composers
         
      </title>
   </head>
   <body>
      <h1>
         Small chamber ensembles - 2-4 Players by New York Women Composers
         
      </h1>
      <h3>Trio for Flute, Viola and Harp</h3>
      <ul>
         <li>1994</li>
         <li>13'38"</li>
         <li>fl, hp, vla</li>
         <li>Theodore Presser</li>
      </ul>
      <p>
         
         <p>Premiered at Queens College in April, 1996 by Sue Ann Kahn, 
            Christine Ims, and Susan Jolles. In 3 movements :
         </p>
         
         <ul>
            
            <li>mvt. 1: 5:01</li>
            
            <li>mvt. 2: 4:11</li>
            
            <li>mvt. 3: 4:26</li>
            
         </ul>  
         
      </p>
      <h3>Charmonium</h3>
      <ul>
         <li>1991</li>
         <li>9'</li>
         <li>2 vln, vla, vc</li>
         <li></li>
      </ul>
      <p>
         
         <p>Commissioned as quartet for the Meridian String Quartet. 
            Sonorous, bold. Moderate difficulty. Tape available.
         </p>
         
      </p>
      <h3>Invention for Flute and Piano</h3>
      <ul>
         <li>1994</li>
         <li></li>
         <li>fl, pn</li>
         <li></li>
      </ul>
      <p>
         <p>3 movements</p>
      </p>
      <h3>Little Trio</h3>
      <ul>
         <li>1984</li>
         <li>4'</li>
         <li>fl, guit, va</li>
         <li>ACA</li>
      </ul>
      <p></p>
      <h3>Dr. Blood's Mermaid Lullaby</h3>
      <ul>
         <li>1980</li>
         <li>3'</li>
         <li>fl or ob, or vn, or vc, pn</li>
         <li>ACA</li>
      </ul>
      <p></p>
      <h3>Trio: Dream in D</h3>
      <ul>
         <li>1980</li>
         <li>10'</li>
         <li>fl, pn, vc, or vn, pn, vc</li>
         <li></li>
      </ul>
      <p>
         
         <p>Rhapsodic. Passionate. Available on CD 
            <cite>
               
               Two by Three
            </cite> 
            from North/South Consonance (1998).
         </p>
         
      </p>
      <h3>Propos II</h3>
      <ul>
         <li>1985</li>
         <li>11'</li>
         <li>2 tpt</li>
         <li></li>
      </ul>
      <p>
         <p>Arrangement from Propos</p>
      </p>
      <h3>Rictus En Mirroir</h3>
      <ul>
         <li>1985</li>
         <li>14'</li>
         <li>fl, ob, hpschd, vc</li>
         <li></li>
      </ul>
      <p></p>
      <hr>
      Copyright 1999 New York Women Composers<br>
      Last Modified: July 28, 1999<br><a href="http://www.macfaq.com/personal.html">
         Elliotte 
         Rusty 
         Harold
         
      </a><br><a href="mailto:elharo@metalab.unc.edu">elharo@metalab.unc.edu</a></body>
</html>

The Or Operator in Match Patterns

Since all four template rules for the HTML element have the same content, we can combine them into a single rule that applies to each of the four using the or operator |

  <xsl:template match="p|ul|li|cite">
    <xsl:copy>
      <xsl:apply-templates/>
    </xsl:copy>
  </xsl:template>

The output is the same

The * wildcard

Right now the descriptions in the input document only use a few HTML tags, but potentially they could use full HTML up to and including tables, images, styles, and more. You could include separate template rules for each of these, but it's easier to specify a rule that applies to all elements.

  <!-- pass unrecognized tags along unchanged -->
  <xsl:template match="*">
    <xsl:copy>
      <xsl:apply-templates/>
    </xsl:copy>
  </xsl:template>

The * matches all elements that are not matched by some more specific rules. It only matches element nodes, though. It does not match nodes for

attributes
comments
processing instructions
namespaces
text

The output is the same in this case, though for a document that used more HTML it might be different.

The node() and @* wildcards

To copy everything including:

attributes
comments
processing instructions
namespaces
text

we have to use greedier wild cards:

@* to copy attribute nodes
node() to copy all other nodes

  <!-- pass unrecognized nodes along unchanged -->
  <xsl:template match="node()|@*">
    <xsl:copy>
      <xsl:apply-templates select="node()|@*"/>
    </xsl:copy>
  </xsl:template>

xt doesn't yet recognize node() in match patterns

The output is the same in this case, though for a document that used more HTML it might be different.

Are we being too greedy?

Perhaps this is too greedy. Do we really only want to recognize HTML in the description element? What if somebody puts HTML in a different, element like instruments? What if somebody makes a mistake and adds an element that shouldn't be there?

I don't think so, but it would be possible to use modes or other techniques to make this default rule only apply inside the description element.

Testing conditions with xsl:if

  <xsl:template match="composition">
    <h3><xsl:value-of select="title"/></h3>

    <ul>
     <xsl:if test="string(date)">
       <li><xsl:value-of select="date"/></li>
     </xsl:if>
     <xsl:if test="string(length)">
       <li><xsl:value-of select="length"/></li>
     </xsl:if>
     <xsl:if test="string(instruments)">
       <li><xsl:value-of select="instruments"/></li>
     </xsl:if>
     <xsl:if test="string(publisher)">
       <li><xsl:value-of select="publisher"/></li>
     </xsl:if>    
    </ul>

    <p><xsl:apply-templates select="description"/></p>    
    
  </xsl:template>

The string() function converts the value of the element to a string
The number() function converts the value of the element to a number
Zero length strings are false
There are all the <, >, =, !=, <= and >= operators you expect

View Transformed Document in browser

The actual HTML output

<html>
   <head>
      <meta http-equiv="Content-Type" content="application/xml; charset=utf-8">
   
      <title>
         Small chamber ensembles - 2-4 Players by New York Women Composers
         
      </title>
   </head>
   <body>
      <h1>
         Small chamber ensembles - 2-4 Players by New York Women Composers
         
      </h1>
      <h3>Trio for Flute, Viola and Harp</h3>
      <ul>
         <li>1994</li>
         <li>13'38"</li>
         <li>fl, hp, vla</li>
         <li>Theodore Presser</li>
      </ul>
      <p>
         <description>
            
            <p>Premiered at Queens College in April, 1996 by Sue Ann Kahn, 
               Christine Ims, and Susan Jolles. In 3 movements :
            </p>
            
            <ul>
               
               <li>mvt. 1: 5:01</li>
               
               <li>mvt. 2: 4:11</li>
               
               <li>mvt. 3: 4:26</li>
               
            </ul>  
            
         </description>
      </p>
      <h3>Charmonium</h3>
      <ul>
         <li>1991</li>
         <li>9'</li>
         <li>2 vln, vla, vc</li>
      </ul>
      <p>
         <description>
            
            <p>Commissioned as quartet for the Meridian String Quartet. 
               Sonorous, bold. Moderate difficulty. Tape available.
            </p>
            
         </description>
      </p>
      <h3>Invention for Flute and Piano</h3>
      <ul>
         <li>1994</li>
         <li>fl, pn</li>
      </ul>
      <p>
         <description>
            <p>3 movements</p>
         </description>
      </p>
      <h3>Little Trio</h3>
      <ul>
         <li>1984</li>
         <li>4'</li>
         <li>fl, guit, va</li>
         <li>ACA</li>
      </ul>
      <p></p>
      <h3>Dr. Blood's Mermaid Lullaby</h3>
      <ul>
         <li>1980</li>
         <li>3'</li>
         <li>fl or ob, or vn, or vc, pn</li>
         <li>ACA</li>
      </ul>
      <p></p>
      <h3>Trio: Dream in D</h3>
      <ul>
         <li>1980</li>
         <li>10'</li>
         <li>fl, pn, vc, or vn, pn, vc</li>
      </ul>
      <p>
         <description>
            
            <p>Rhapsodic. Passionate. Available on CD 
               <cite>
                  <a href="http://www.amazon.com/exec/obidos/ASIN/B000007NMH/qid=913265342/sr=1-2/" shape="rect">
                     Two by Three
                  </a>
               </cite> 
               from North/South Consonance (1998).
            </p>
            
         </description>
      </p>
      <h3>Propos II</h3>
      <ul>
         <li>1985</li>
         <li>11'</li>
         <li>2 tpt</li>
      </ul>
      <p>
         <description>
            <p>Arrangement from Propos</p>
         </description>
      </p>
      <h3>Rictus En Mirroir</h3>
      <ul>
         <li>1985</li>
         <li>14'</li>
         <li>fl, ob, hpschd, vc</li>
      </ul>
      <p></p>
      <hr>
      Copyright 1999 New York Women Composers<br>
      Last Modified: July 28, 1999<br><a href="http://www.macfaq.com/personal.html">
         Elliotte 
         Rusty 
         Harold
         
      </a><br><a href="mailto:elharo@metalab.unc.edu">elharo@metalab.unc.edu</a></body>
</html>

Matching composers with compositions

The composers and their compositions are linked through the the id attribute of the composer element and the composer attribute of the composition element.

  <composer id="c3">
    <name>
      <first_name>Beth</first_name> 
      <middle_name></middle_name> 
      <last_name>Anderson</last_name>
    </name>
  </composer>
    
  <composition composer="c3">
    <title>Trio: Dream in D</title>
    <date><year>(1980)</year></date> 
    <length>10'</length>
    <instruments>fl, pn, vc, or vn, pn, vc</instruments>
    <description>
      Rhapsodic. Passionate. Available on CD 
      <cite><a href="http://www.amazon.com/exec/obidos/ASIN/B000007NMH/qid=913265342/sr%3D1-2/">
       Two by Three</a></cite> from North/South Consonance (1998).
    </description> 
    <publisher></publisher>
  </composition>

Matching composers with compositions

  <xsl:template match="catalog">
    <head>
       <title><xsl:value-of select="category"/></title>      
    </head>
    <body>
       <h1><xsl:value-of select="category"/></h1>      
       <xsl:apply-templates select="composer"/>
       <hr/>
       Copyright <xsl:value-of select="copyright"/><br/>
       Last Modified: <xsl:value-of select="last_updated"/><br/>
       <xsl:apply-templates select="maintainer"/>
    </body>
  </xsl:template>
  
  <xsl:template match="composer">
    <h2><xsl:value-of select="name"/></h2>
    <xsl:apply-templates select="../composition[@composer=current()/@id]"/>
  </xsl:template>

.. selects the parent element
/ selects a child of the context node
Square braces [] include a predicate to winnow down the selected nodes
The current() function refers to the matched composer element
@composer() and @id take the value of the composer attribute and the id attribute
The = operator compares the to attributes

View Transformed Document in browser

The actual HTML output

<html>
   <head>
      <meta http-equiv="Content-Type" content="application/xml; charset=utf-8">
   
      <title>
         Small chamber ensembles - 2-4 Players by New York Women Composers
         
      </title>
   </head>
   <body>
      <h1>
         Small chamber ensembles - 2-4 Players by New York Women Composers
         
      </h1>
      <h2>
         Julie 
         
         Mandel
         
      </h2>
      <h3>Trio for Flute, Viola and Harp</h3>
      <ul>
         <li>1994</li>
         <li>13'38"</li>
         <li>fl, hp, vla</li>
         <li>Theodore Presser</li>
      </ul>
      <p>
         <description>
            
            <p>Premiered at Queens College in April, 1996 by Sue Ann Kahn, 
               Christine Ims, and Susan Jolles. In 3 movements :
            </p>
            
            <ul>
               
               <li>mvt. 1: 5:01</li>
               
               <li>mvt. 2: 4:11</li>
               
               <li>mvt. 3: 4:26</li>
               
            </ul>  
            
         </description>
      </p>
      <h3>Invention for Flute and Piano</h3>
      <ul>
         <li>1994</li>
         <li>fl, pn</li>
      </ul>
      <p>
         <description>
            <p>3 movements</p>
         </description>
      </p>
      <h2>
         Margaret 
         De 
         Wys
         
      </h2>
      <h3>Charmonium</h3>
      <ul>
         <li>1991</li>
         <li>9'</li>
         <li>2 vln, vla, vc</li>
      </ul>
      <p>
         <description>
            
            <p>Commissioned as quartet for the Meridian String Quartet. 
               Sonorous, bold. Moderate difficulty. Tape available.
            </p>
            
         </description>
      </p>
      <h2>
         Beth 
         
         Anderson
         
      </h2>
      <h3>Little Trio</h3>
      <ul>
         <li>1984</li>
         <li>4'</li>
         <li>fl, guit, va</li>
         <li>ACA</li>
      </ul>
      <p></p>
      <h3>Dr. Blood's Mermaid Lullaby</h3>
      <ul>
         <li>1980</li>
         <li>3'</li>
         <li>fl or ob, or vn, or vc, pn</li>
         <li>ACA</li>
      </ul>
      <p></p>
      <h3>Trio: Dream in D</h3>
      <ul>
         <li>1980</li>
         <li>10'</li>
         <li>fl, pn, vc, or vn, pn, vc</li>
      </ul>
      <p>
         <description>
            
            <p>Rhapsodic. Passionate. Available on CD 
               <cite>
                  <a href="http://www.amazon.com/exec/obidos/ASIN/B000007NMH/qid=913265342/sr=1-2/" shape="rect">
                     Two by Three
                  </a>
               </cite> 
               from North/South Consonance (1998).
            </p>
            
         </description>
      </p>
      <h2>
         Linda 
         
         Bouchard
         
      </h2>
      <h3>Propos II</h3>
      <ul>
         <li>1985</li>
         <li>11'</li>
         <li>2 tpt</li>
      </ul>
      <p>
         <description>
            <p>Arrangement from Propos</p>
         </description>
      </p>
      <h3>Rictus En Mirroir</h3>
      <ul>
         <li>1985</li>
         <li>14'</li>
         <li>fl, ob, hpschd, vc</li>
      </ul>
      <p></p>
      <hr>
      Copyright 1999 New York Women Composers<br>
      Last Modified: July 28, 1999<br><a href="http://www.macfaq.com/personal.html">
         Elliotte 
         Rusty 
         Harold
         
      </a><br><a href="mailto:elharo@metalab.unc.edu">elharo@metalab.unc.edu</a></body>
</html>

Sorting with xsl:sort

  <xsl:template match="catalog">
    <head>
       <title><xsl:value-of select="category"/></title>      
    </head>
    <body>
       <h1><xsl:value-of select="category"/></h1>      
       <xsl:apply-templates select="composer">
         <xsl:sort select="name/last_name"/>
       </xsl:apply-templates>
       <hr/>
       Copyright <xsl:value-of select="copyright"/><br/>
       Last Modified: <xsl:value-of select="last_updated"/><br/>
       <xsl:apply-templates select="maintainer"/>
    </body>
  </xsl:template>

The select attribute provides the key to sort by
Must be a child of xsl:apply-templates or xsl:for-each

View Transformed Document in browser

The actual HTML output

<html>
   <head>
      <meta http-equiv="Content-Type" content="application/xml; charset=utf-8">
   
      <title>
         Small chamber ensembles - 2-4 Players by New York Women Composers
         
      </title>
   </head>
   <body>
      <h1>
         Small chamber ensembles - 2-4 Players by New York Women Composers
         
      </h1>
      <h2>
         Beth 
         
         Anderson
         
      </h2>
      <h3>Little Trio</h3>
      <ul>
         <li>1984</li>
         <li>4'</li>
         <li>fl, guit, va</li>
         <li>ACA</li>
      </ul>
      <p></p>
      <h3>Dr. Blood's Mermaid Lullaby</h3>
      <ul>
         <li>1980</li>
         <li>3'</li>
         <li>fl or ob, or vn, or vc, pn</li>
         <li>ACA</li>
      </ul>
      <p></p>
      <h3>Trio: Dream in D</h3>
      <ul>
         <li>1980</li>
         <li>10'</li>
         <li>fl, pn, vc, or vn, pn, vc</li>
      </ul>
      <p>
         <description>
            
            <p>Rhapsodic. Passionate. Available on CD 
               <cite>
                  <a href="http://www.amazon.com/exec/obidos/ASIN/B000007NMH/qid=913265342/sr=1-2/" shape="rect">
                     Two by Three
                  </a>
               </cite> 
               from North/South Consonance (1998).
            </p>
            
         </description>
      </p>
      <h2>
         Linda 
         
         Bouchard
         
      </h2>
      <h3>Propos II</h3>
      <ul>
         <li>1985</li>
         <li>11'</li>
         <li>2 tpt</li>
      </ul>
      <p>
         <description>
            <p>Arrangement from Propos</p>
         </description>
      </p>
      <h3>Rictus En Mirroir</h3>
      <ul>
         <li>1985</li>
         <li>14'</li>
         <li>fl, ob, hpschd, vc</li>
      </ul>
      <p></p>
      <h2>
         Julie 
         
         Mandel
         
      </h2>
      <h3>Trio for Flute, Viola and Harp</h3>
      <ul>
         <li>1994</li>
         <li>13'38"</li>
         <li>fl, hp, vla</li>
         <li>Theodore Presser</li>
      </ul>
      <p>
         <description>
            
            <p>Premiered at Queens College in April, 1996 by Sue Ann Kahn, 
               Christine Ims, and Susan Jolles. In 3 movements :
            </p>
            
            <ul>
               
               <li>mvt. 1: 5:01</li>
               
               <li>mvt. 2: 4:11</li>
               
               <li>mvt. 3: 4:26</li>
               
            </ul>  
            
         </description>
      </p>
      <h3>Invention for Flute and Piano</h3>
      <ul>
         <li>1994</li>
         <li>fl, pn</li>
      </ul>
      <p>
         <description>
            <p>3 movements</p>
         </description>
      </p>
      <h2>
         Margaret 
         De 
         Wys
         
      </h2>
      <h3>Charmonium</h3>
      <ul>
         <li>1991</li>
         <li>9'</li>
         <li>2 vln, vla, vc</li>
      </ul>
      <p>
         <description>
            
            <p>Commissioned as quartet for the Meridian String Quartet. 
               Sonorous, bold. Moderate difficulty. Tape available.
            </p>
            
         </description>
      </p>
      <hr>
      Copyright 1999 New York Women Composers<br>
      Last Modified: July 28, 1999<br><a href="http://www.macfaq.com/personal.html">
         Elliotte 
         Rusty 
         Harold
         
      </a><br><a href="mailto:elharo@metalab.unc.edu">elharo@metalab.unc.edu</a></body>
</html>

Multiple Key Sorts

  <xsl:template match="catalog">
    <head>
       <title><xsl:value-of select="category"/></title>      
    </head>
    <body>
       <h1><xsl:value-of select="category"/></h1>      
       <xsl:apply-templates select="composer">
         <xsl:sort select="name/last_name"/>
         <xsl:sort select="name/first_name"/>
         <xsl:sort select="name/middle_name"/>
       </xsl:apply-templates>
       <hr/>
       Copyright <xsl:value-of select="copyright"/><br/>
       Last Modified: <xsl:value-of select="last_updated"/><br/>
       <xsl:apply-templates select="maintainer"/>
    </body>
  </xsl:template>

View Transformed Document in browser

The actual HTML output

<html>
   <head>
      <meta http-equiv="Content-Type" content="application/xml; charset=utf-8">
   
      <title>
         Small chamber ensembles - 2-4 Players by New York Women Composers
         
      </title>
   </head>
   <body>
      <h1>
         Small chamber ensembles - 2-4 Players by New York Women Composers
         
      </h1>
      <h2>
         Beth 
         
         Anderson
         
      </h2>
      <h3>Little Trio</h3>
      <ul>
         <li>1984</li>
         <li>4'</li>
         <li>fl, guit, va</li>
         <li>ACA</li>
      </ul>
      <p></p>
      <h3>Dr. Blood's Mermaid Lullaby</h3>
      <ul>
         <li>1980</li>
         <li>3'</li>
         <li>fl or ob, or vn, or vc, pn</li>
         <li>ACA</li>
      </ul>
      <p></p>
      <h3>Trio: Dream in D</h3>
      <ul>
         <li>1980</li>
         <li>10'</li>
         <li>fl, pn, vc, or vn, pn, vc</li>
      </ul>
      <p>
         <description>
            
            <p>Rhapsodic. Passionate. Available on CD 
               <cite>
                  <a href="http://www.amazon.com/exec/obidos/ASIN/B000007NMH/qid=913265342/sr=1-2/" shape="rect">
                     Two by Three
                  </a>
               </cite> 
               from North/South Consonance (1998).
            </p>
            
         </description>
      </p>
      <h2>
         Linda 
         
         Bouchard
         
      </h2>
      <h3>Propos II</h3>
      <ul>
         <li>1985</li>
         <li>11'</li>
         <li>2 tpt</li>
      </ul>
      <p>
         <description>
            <p>Arrangement from Propos</p>
         </description>
      </p>
      <h3>Rictus En Mirroir</h3>
      <ul>
         <li>1985</li>
         <li>14'</li>
         <li>fl, ob, hpschd, vc</li>
      </ul>
      <p></p>
      <h2>
         Julie 
         
         Mandel
         
      </h2>
      <h3>Trio for Flute, Viola and Harp</h3>
      <ul>
         <li>1994</li>
         <li>13'38"</li>
         <li>fl, hp, vla</li>
         <li>Theodore Presser</li>
      </ul>
      <p>
         <description>
            
            <p>Premiered at Queens College in April, 1996 by Sue Ann Kahn, 
               Christine Ims, and Susan Jolles. In 3 movements :
            </p>
            
            <ul>
               
               <li>mvt. 1: 5:01</li>
               
               <li>mvt. 2: 4:11</li>
               
               <li>mvt. 3: 4:26</li>
               
            </ul>  
            
         </description>
      </p>
      <h3>Invention for Flute and Piano</h3>
      <ul>
         <li>1994</li>
         <li>fl, pn</li>
      </ul>
      <p>
         <description>
            <p>3 movements</p>
         </description>
      </p>
      <h2>
         Margaret 
         De 
         Wys
         
      </h2>
      <h3>Charmonium</h3>
      <ul>
         <li>1991</li>
         <li>9'</li>
         <li>2 vln, vla, vc</li>
      </ul>
      <p>
         <description>
            
            <p>Commissioned as quartet for the Meridian String Quartet. 
               Sonorous, bold. Moderate difficulty. Tape available.
            </p>
            
         </description>
      </p>
      <hr>
      Copyright 1999 New York Women Composers<br>
      Last Modified: July 28, 1999<br><a href="http://www.macfaq.com/personal.html">
         Elliotte 
         Rusty 
         Harold
         
      </a><br><a href="mailto:elharo@metalab.unc.edu">elharo@metalab.unc.edu</a></body>
</html>

Sorting by Composition Title

Sorting by composition title is equally straight-forward but we have to do it in a separate apply-templates element

  <xsl:template match="catalog">
    <head>
       <title><xsl:value-of select="category"/></title>      
    </head>
    <body>
       <h1><xsl:value-of select="category"/></h1>      
       <xsl:apply-templates select="composer">
         <xsl:sort select="name/last_name"/>
         <xsl:sort select="name/first_name"/>
         <xsl:sort select="name/middle_name"/>
       </xsl:apply-templates>
       <hr/>
       Copyright <xsl:value-of select="copyright"/><br/>
       Last Modified: <xsl:value-of select="last_updated"/><br/>
       <xsl:apply-templates select="maintainer"/>
    </body>
  </xsl:template>
  
  <xsl:template match="composer">
    <h2><xsl:value-of select="name"/></h2>
    <xsl:apply-templates select="../composition[@composer=current()/@id]">
       <xsl:sort select="title"/>      
    </xsl:apply-templates>
  </xsl:template>

View Transformed Document in browser

The actual HTML output

<html>
   <head>
      <meta http-equiv="Content-Type" content="application/xml; charset=utf-8">
   
      <title>
         Small chamber ensembles - 2-4 Players by New York Women Composers
         
      </title>
   </head>
   <body>
      <h1>
         Small chamber ensembles - 2-4 Players by New York Women Composers
         
      </h1>
      <h2>
         Beth 
         
         Anderson
         
      </h2>
      <h3>Dr. Blood's Mermaid Lullaby</h3>
      <ul>
         <li>1980</li>
         <li>3'</li>
         <li>fl or ob, or vn, or vc, pn</li>
         <li>ACA</li>
      </ul>
      <p></p>
      <h3>Little Trio</h3>
      <ul>
         <li>1984</li>
         <li>4'</li>
         <li>fl, guit, va</li>
         <li>ACA</li>
      </ul>
      <p></p>
      <h3>Trio: Dream in D</h3>
      <ul>
         <li>1980</li>
         <li>10'</li>
         <li>fl, pn, vc, or vn, pn, vc</li>
      </ul>
      <p>
         <description>
            
            <p>Rhapsodic. Passionate. Available on CD 
               <cite>
                  <a href="http://www.amazon.com/exec/obidos/ASIN/B000007NMH/qid=913265342/sr=1-2/" shape="rect">
                     Two by Three
                  </a>
               </cite> 
               from North/South Consonance (1998).
            </p>
            
         </description>
      </p>
      <h2>
         Linda 
         
         Bouchard
         
      </h2>
      <h3>Propos II</h3>
      <ul>
         <li>1985</li>
         <li>11'</li>
         <li>2 tpt</li>
      </ul>
      <p>
         <description>
            <p>Arrangement from Propos</p>
         </description>
      </p>
      <h3>Rictus En Mirroir</h3>
      <ul>
         <li>1985</li>
         <li>14'</li>
         <li>fl, ob, hpschd, vc</li>
      </ul>
      <p></p>
      <h2>
         Julie 
         
         Mandel
         
      </h2>
      <h3>Invention for Flute and Piano</h3>
      <ul>
         <li>1994</li>
         <li>fl, pn</li>
      </ul>
      <p>
         <description>
            <p>3 movements</p>
         </description>
      </p>
      <h3>Trio for Flute, Viola and Harp</h3>
      <ul>
         <li>1994</li>
         <li>13'38"</li>
         <li>fl, hp, vla</li>
         <li>Theodore Presser</li>
      </ul>
      <p>
         <description>
            
            <p>Premiered at Queens College in April, 1996 by Sue Ann Kahn, 
               Christine Ims, and Susan Jolles. In 3 movements :
            </p>
            
            <ul>
               
               <li>mvt. 1: 5:01</li>
               
               <li>mvt. 2: 4:11</li>
               
               <li>mvt. 3: 4:26</li>
               
            </ul>  
            
         </description>
      </p>
      <h2>
         Margaret 
         De 
         Wys
         
      </h2>
      <h3>Charmonium</h3>
      <ul>
         <li>1991</li>
         <li>9'</li>
         <li>2 vln, vla, vc</li>
      </ul>
      <p>
         <description>
            
            <p>Commissioned as quartet for the Meridian String Quartet. 
               Sonorous, bold. Moderate difficulty. Tape available.
            </p>
            
         </description>
      </p>
      <hr>
      Copyright 1999 New York Women Composers<br>
      Last Modified: July 28, 1999<br><a href="http://www.macfaq.com/personal.html">
         Elliotte 
         Rusty 
         Harold
         
      </a><br><a href="mailto:elharo@metalab.unc.edu">elharo@metalab.unc.edu</a></body>
</html>

xsl:for-each

  <xsl:template match="catalog">
    <head>
       <title><xsl:value-of select="category"/></title>      
    </head>
    <body>
       <!-- Header -->            
       <h1><xsl:value-of select="category"/></h1>
       <ul>
         <xsl:for-each select="composition">
           <li><xsl:value-of select="title"/></li>
         </xsl:for-each>
       </ul>
       
       <!-- Body -->            
       <xsl:apply-templates select="composer">
         <xsl:sort select="name/last_name"/>
         <xsl:sort select="name/first_name"/>
         <xsl:sort select="name/middle_name"/>
       </xsl:apply-templates>
       
       <!-- Signature -->      
       <hr/>
       Copyright <xsl:value-of select="copyright"/><br/>
       Last Modified: <xsl:value-of select="last_updated"/><br/>
       <xsl:apply-templates select="maintainer"/>
    </body>
  </xsl:template>

. selects the context node
xsl:for-each iterates through the selected nodes, setting each one to the current node in turn but does not apply templates to that node.

View Transformed Document in browser

The actual HTML output

<html>
   <head>
      <meta http-equiv="Content-Type" content="application/xml; charset=utf-8">
   
      <title>
         Small chamber ensembles - 2-4 Players by New York Women Composers
         
      </title>
   </head>
   <body>
      <h1>
         Small chamber ensembles - 2-4 Players by New York Women Composers
         
      </h1>
      <ul>
         <li>Trio for Flute, Viola and Harp</li>
         <li>Charmonium</li>
         <li>Invention for Flute and Piano</li>
         <li>Little Trio</li>
         <li>Dr. Blood's Mermaid Lullaby</li>
         <li>Trio: Dream in D</li>
         <li>Propos II</li>
         <li>Rictus En Mirroir</li>
      </ul>
      <h2>
         Beth 
         
         Anderson
         
      </h2>
      <h3>Dr. Blood's Mermaid Lullaby</h3>
      <ul>
         <li>1980</li>
         <li>3'</li>
         <li>fl or ob, or vn, or vc, pn</li>
         <li>ACA</li>
      </ul>
      <p></p>
      <h3>Little Trio</h3>
      <ul>
         <li>1984</li>
         <li>4'</li>
         <li>fl, guit, va</li>
         <li>ACA</li>
      </ul>
      <p></p>
      <h3>Trio: Dream in D</h3>
      <ul>
         <li>1980</li>
         <li>10'</li>
         <li>fl, pn, vc, or vn, pn, vc</li>
      </ul>
      <p>
         <description>
            
            <p>Rhapsodic. Passionate. Available on CD 
               <cite>
                  <a href="http://www.amazon.com/exec/obidos/ASIN/B000007NMH/qid=913265342/sr=1-2/" shape="rect">
                     Two by Three
                  </a>
               </cite> 
               from North/South Consonance (1998).
            </p>
            
         </description>
      </p>
      <h2>
         Linda 
         
         Bouchard
         
      </h2>
      <h3>Propos II</h3>
      <ul>
         <li>1985</li>
         <li>11'</li>
         <li>2 tpt</li>
      </ul>
      <p>
         <description>
            <p>Arrangement from Propos</p>
         </description>
      </p>
      <h3>Rictus En Mirroir</h3>
      <ul>
         <li>1985</li>
         <li>14'</li>
         <li>fl, ob, hpschd, vc</li>
      </ul>
      <p></p>
      <h2>
         Julie 
         
         Mandel
         
      </h2>
      <h3>Invention for Flute and Piano</h3>
      <ul>
         <li>1994</li>
         <li>fl, pn</li>
      </ul>
      <p>
         <description>
            <p>3 movements</p>
         </description>
      </p>
      <h3>Trio for Flute, Viola and Harp</h3>
      <ul>
         <li>1994</li>
         <li>13'38"</li>
         <li>fl, hp, vla</li>
         <li>Theodore Presser</li>
      </ul>
      <p>
         <description>
            
            <p>Premiered at Queens College in April, 1996 by Sue Ann Kahn, 
               Christine Ims, and Susan Jolles. In 3 movements :
            </p>
            
            <ul>
               
               <li>mvt. 1: 5:01</li>
               
               <li>mvt. 2: 4:11</li>
               
               <li>mvt. 3: 4:26</li>
               
            </ul>  
            
         </description>
      </p>
      <h2>
         Margaret 
         De 
         Wys
         
      </h2>
      <h3>Charmonium</h3>
      <ul>
         <li>1991</li>
         <li>9'</li>
         <li>2 vln, vla, vc</li>
      </ul>
      <p>
         <description>
            
            <p>Commissioned as quartet for the Meridian String Quartet. 
               Sonorous, bold. Moderate difficulty. Tape available.
            </p>
            
         </description>
      </p>
      <hr>
      Copyright 1999 New York Women Composers<br>
      Last Modified: July 28, 1999<br><a href="http://www.macfaq.com/personal.html">
         Elliotte 
         Rusty 
         Harold
         
      </a><br><a href="mailto:elharo@metalab.unc.edu">elharo@metalab.unc.edu</a></body>
</html>

Sorting the Table of Contents

xsl:for-each can have an xsl:sort child just like xsl:apply-templates

  <xsl:template match="catalog">
    <head>
       <title><xsl:value-of select="category"/></title>      
    </head>
    <body>
       <!-- Header -->            
       <h1><xsl:value-of select="category"/></h1>
       <ul>
         <xsl:for-each select="composition">
           <xsl:sort select="title"/>
           <li><xsl:value-of select="title"/></li>
         </xsl:for-each>
       </ul>
       
       <!-- Body -->            
       <xsl:apply-templates select="composer">
         <xsl:sort select="name/last_name"/>
         <xsl:sort select="name/first_name"/>
         <xsl:sort select="name/middle_name"/>
       </xsl:apply-templates>
       
       <!-- Signature -->      
       <hr/>
       Copyright <xsl:value-of select="copyright"/><br/>
       Last Modified: <xsl:value-of select="last_updated"/><br/>
       <xsl:apply-templates select="maintainer"/>
    </body>
  </xsl:template>

View Transformed Document in browser

Adding Links from the Table of Contents

We need to add <a name="some_name">title</a> around each compositon title so we have something to link to.
The generate-id() function will choose a unique ID for a particular element.

Here's the new template for the composition

  <xsl:template match="composition">
    <h3>
      <a name="{generate-id()}">
        <xsl:value-of select="title"/>
      </a>
    </h3>

    <ul>
     <xsl:if test="string(date)">
       <li><xsl:value-of select="date"/></li>
     </xsl:if>
     <xsl:if test="string(length)">
       <li><xsl:value-of select="length"/></li>
     </xsl:if>
     <xsl:if test="string(instruments)">
       <li><xsl:value-of select="instruments"/></li>
     </xsl:if>
     <xsl:if test="string(publisher)">
       <li><xsl:value-of select="publisher"/></li>
     </xsl:if>    
    </ul>

    <p><xsl:apply-templates select="description"/></p>    
    
  </xsl:template>

Here's the new template for the tabel of contents link

   <xsl:template match="catalog">
    <head>
       <title><xsl:value-of select="category"/></title>      
    </head>
    <body>
       <!-- Header -->            
       <h1><xsl:value-of select="category"/></h1>
       <ul>
         <xsl:for-each select="composition">
           <xsl:sort select="title"/>
           <li>
             <a href="#{generate-id()}">
               <xsl:value-of select="title"/>
             </a>
           </li>
         </xsl:for-each>
       </ul>
       
       <!-- Body -->            
       <xsl:apply-templates select="composer">
         <xsl:sort select="name/last_name"/>
         <xsl:sort select="name/first_name"/>
         <xsl:sort select="name/middle_name"/>
       </xsl:apply-templates>
       
       <!-- Signature -->      
       <hr/>
       Copyright <xsl:value-of select="copyright"/><br/>
       Last Modified: <xsl:value-of select="last_updated"/><br/>
       <xsl:apply-templates select="maintainer"/>
    </body>
  </xsl:template>

Although the ID is generated in two separate places, it is generated for the same node. Consequently, they are the same.

View Transformed Document in browser

The actual HTML output

<html>
   <head>
      <meta http-equiv="Content-Type" content="application/xml; charset=utf-8">
   
      <title>
         Small chamber ensembles - 2-4 Players by New York Women Composers
         
      </title>
   </head>
   <body>
      <h1>
         Small chamber ensembles - 2-4 Players by New York Women Composers
         
      </h1>
      <ul>
         <li><a href="#b1ac21">Charmonium</a></li>
         <li><a href="#b1ac27">Dr. Blood's Mermaid Lullaby</a></li>
         <li><a href="#b1ac23">Invention for Flute and Piano</a></li>
         <li><a href="#b1ac25">Little Trio</a></li>
         <li><a href="#b1ac31">Propos II</a></li>
         <li><a href="#b1ac33">Rictus En Mirroir</a></li>
         <li><a href="#b1ac19">Trio for Flute, Viola and Harp</a></li>
         <li><a href="#b1ac29">Trio: Dream in D</a></li>
      </ul>
      <h2>
         Beth 
         
         Anderson
         
      </h2>
      <h3><a name="b1ac27">Dr. Blood's Mermaid Lullaby</a></h3>
      <ul>
         <li>1980</li>
         <li>3'</li>
         <li>fl or ob, or vn, or vc, pn</li>
         <li>ACA</li>
      </ul>
      <p></p>
      <h3><a name="b1ac25">Little Trio</a></h3>
      <ul>
         <li>1984</li>
         <li>4'</li>
         <li>fl, guit, va</li>
         <li>ACA</li>
      </ul>
      <p></p>
      <h3><a name="b1ac29">Trio: Dream in D</a></h3>
      <ul>
         <li>1980</li>
         <li>10'</li>
         <li>fl, pn, vc, or vn, pn, vc</li>
      </ul>
      <p>
         <description>
            
            <p>Rhapsodic. Passionate. Available on CD 
               <cite>
                  <a href="http://www.amazon.com/exec/obidos/ASIN/B000007NMH/qid=913265342/sr=1-2/" shape="rect">
                     Two by Three
                  </a>
               </cite> 
               from North/South Consonance (1998).
            </p>
            
         </description>
      </p>
      <h2>
         Linda 
         
         Bouchard
         
      </h2>
      <h3><a name="b1ac31">Propos II</a></h3>
      <ul>
         <li>1985</li>
         <li>11'</li>
         <li>2 tpt</li>
      </ul>
      <p>
         <description>
            <p>Arrangement from Propos</p>
         </description>
      </p>
      <h3><a name="b1ac33">Rictus En Mirroir</a></h3>
      <ul>
         <li>1985</li>
         <li>14'</li>
         <li>fl, ob, hpschd, vc</li>
      </ul>
      <p></p>
      <h2>
         Julie 
         
         Mandel
         
      </h2>
      <h3><a name="b1ac23">Invention for Flute and Piano</a></h3>
      <ul>
         <li>1994</li>
         <li>fl, pn</li>
      </ul>
      <p>
         <description>
            <p>3 movements</p>
         </description>
      </p>
      <h3><a name="b1ac19">Trio for Flute, Viola and Harp</a></h3>
      <ul>
         <li>1994</li>
         <li>13'38"</li>
         <li>fl, hp, vla</li>
         <li>Theodore Presser</li>
      </ul>
      <p>
         <description>
            
            <p>Premiered at Queens College in April, 1996 by Sue Ann Kahn, 
               Christine Ims, and Susan Jolles. In 3 movements :
            </p>
            
            <ul>
               
               <li>mvt. 1: 5:01</li>
               
               <li>mvt. 2: 4:11</li>
               
               <li>mvt. 3: 4:26</li>
               
            </ul>  
            
         </description>
      </p>
      <h2>
         Margaret 
         De 
         Wys
         
      </h2>
      <h3><a name="b1ac21">Charmonium</a></h3>
      <ul>
         <li>1991</li>
         <li>9'</li>
         <li>2 vln, vla, vc</li>
      </ul>
      <p>
         <description>
            
            <p>Commissioned as quartet for the Meridian String Quartet. 
               Sonorous, bold. Moderate difficulty. Tape available.
            </p>
            
         </description>
      </p>
      <hr>
      Copyright 1999 New York Women Composers<br>
      Last Modified: July 28, 1999<br><a href="http://www.macfaq.com/personal.html">
         Elliotte 
         Rusty 
         Harold
         
      </a><br><a href="mailto:elharo@metalab.unc.edu">elharo@metalab.unc.edu</a></body>
</html>

Where Does the XML Transformation Happen?

There are three primary ways XML documents are transformed into other formats, such as HTML, with an XSL style sheet:

The XML document and associated style sheet are both served to the client (Web browser), which then transforms the document as specified by the style sheet and presents it to the user.
The server applies an XSL style sheet to an XML document to transform it to some other format (generally HTML) and sends the transformed document to the client (Web browser).
A third program transforms the original XML document into some other format (often HTML) before the document is placed on the server. Both server and client only deal with the post-transform document.

Client Side Processing

Attaching an XSLT style sheet to an XML document is easy. Simply insert an xml-stylesheet processing instruction in the prolog immediately after the XML declaration. This processing instruction should have a type attribute with the value text/xml or application/xml+xslt and an href attribute whose value is a URL pointing to the style sheet. For example:

<?xml version="1.0"?>
<?xml-stylesheet type="text/xml" href="compositions.xsl"?>

This is also how you attach a CSS style sheet to a document. The only difference here is that the type attribute has the value text/xml instead of text/css.

A style sheet that works with Internet Explorer 5

<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet xmlns:xsl="http://www.w3.org/TR/WD-xsl">

  <xsl:template match="/">
    <html>
      <xsl:apply-templates select="catalog"/>
    </html>
  </xsl:template>

  <xsl:template match="catalog">
    <body>
      <xsl:apply-templates select="composition"/>
    </body>
  </xsl:template>

  <xsl:template match="composition">
    <h3><xsl:value-of select="name"/></h3>
  </xsl:template>

</xsl:stylesheet>

What else does XSLT have?

Many more ways to select and match elements including descendants, attributes, comments, processing instructions, and text.
Many more tests for predicates including basic arithmetic operations
The xsl:element, xsl:attribute, xsl:processing-instruction, xsl:comment, and xsl:text elements can output elements, attributes, processing instructions, comments, and text calculated from data in the input document.
The xsl:copy-of element to copy complete nodes from the input to the output
Parameters for passing arguments to templates
Modes for reprocessing the same element in a different fashion
Recursion
The xsl:variable element defines named constants that can clarify your code.
Named templates, variables, and attribute sets help you reuse common template code.
The xsl:choose and xsl:when elements let you select one of several possibilities depending on a condition.
The xsl:import and xsl:include elements merge rules from different style sheets.
The xsl:message element
Various attributes of the xsl:output element allow you to specify the output document's format, XML declaration, document type declaration, indentation, encoding and MIME type.

What does XSLT not have?

A general regular expression language
Non-final variables (hence no side effects)
Loops

Summary

The Extensible Style Language (XSL) comprises two separate XML applications for transforming and formatting XML documents.
An XSL transformation applies rules to a tree read from an XML document to transform it into an output tree written as an XML document.
An XSL template rule is an xsl:template element with a match attribute. Nodes in the input tree are compared against the patterns of the match attributes of the different template elements. When a match is found, the contents of the template are output.
The value of a node is a pure text (no markup) string containing the contents of the node. This can be calculated by the xsl:value-of element.
The xsl:apply-templates element continues processing the children of the current node
The xsl:if element produces output if, and only if, its test attribute is true.
The xsl:number element inserts the number specified by its value attribute into the output using a specified number format given by the format attribute.
The xsl:sort element can reorder the input nodes before copying them to the output.

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