Namespaces

Elliotte Rusty Harold

Software Development 2001 East

Thurday, August 30, 2001

elharo@metalab.unc.edu

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

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An XSLT stylesheet that transforms a style sheet in an older version of the XSLT specification to a style sheet in a newer version of the XSLT specification.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.

URIs

Uniform Resource Identifier
Two kinds:
- URLs: Uniform Resource Locators
- URNs: Uniform Resource Names
Which should be used for namespaces?
Absolute vs. relative

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

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/2000/svg" 
 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:mathml="http://www.w3.org/1998/Math/MathML">
  <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/2000/svg" 
             width="12cm" height="10cm">
      <svg:ellipse rx="110" ry="130" />
      <svg:rect x="4cm" y="1cm" width="3cm" height="6cm" />
    </svg:svg>
    <xhtml:p>The equation for ellipses????</xhtml:p>
    <mathml:math>
	   <mathml:mrow>
	     <mathml:mi>f(0)</mathml:mi>
	     <mathml:mo>=</mathml:mo>
	     <mathml:mn>0</mathml:mn>
	   </mathml:mrow>
     </mathml:math>
    <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/2000/svg">

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

Namespaces and Attributes

An attribute can be placed in a namespace by prefixing its name.
Normally only used for global atributes that can appear on any element such as XLink attributes rather than attributes that are tied to a specific element.
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.

<xhtml:html xmlns:xhtml="http://www.w3.org/1999/xhtml"
            xmlns:xlink="http://www.w3.org/1999/xlink">
  <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/2000/svg" 
             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>

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.

The Default Namespace

Indicates 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.

Multiple default namespaces

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/1999/xlink">
  <head><title>Three Namespaces</title></head>
  <body>
    <h1 align="center">An Ellipse and a Rectangle</h1>
    <svg xmlns="http://www.w3.org/2000/svg" 
         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/2000/svg">

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

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 character by character

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

How Parsers Handle Namespaces

Namespaces were added to XML 1.0 after the fact, but care was taken to ensure backwards compatibility.
An XML 1.0 parser that does not know about namespaces will most likely not have any troubles reading a document that uses namespaces.
A namespace aware parser also checks to see that all prefixes are mapped to URIs. Otherwise it behaves almost exactly like a non-namespace aware parser.
Other software that sits on top of the raw XML parser, an XSLT engine for example, may treat elements differently depending on what namespace they belong to. However, the XML parser itself mostly doesn't care as long as all well-formedness and namespace constraints are met.
A possible exception occurs in the unlikely event that elements with different prefixes belong to the same namespace or elements with the same prefix belong to different namespaces
Many parsers have the option of whether to report namespace violations so that you can turn namespace processing on or off as you see fit.

Namespaces and DTDs

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

Parameter Entity References for Namespace Prefixes

Must use double indirection

<!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' >

<!ELEMENT %mathml-real; (%mathml-exp; | %mathml-abs;)*>

Only works in external DTD subset

Namespaces and Schemas

URI matters; prefix doesn't
Do not have to declare xmlns and xmlns:prefix attributes
Namespaces are used on elements and attribute values, but not attribute names

A Song with a Namespace

<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<SONG xmlns="http://ibiblio.org/xml/namespace/song"
      xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
      xsi:schemaLocation = 
       "http://ibiblio.org/xml/namespace/song namespace_song.xsd"
>
  <TITLE>Hot Cop</TITLE>
  <PHOTO ALT="Victor Willis in Cop Outfit" WIDTH="100" HEIGHT="200"/>
  <COMPOSER>Jacques Morali</COMPOSER>
  <COMPOSER>Henri Belolo</COMPOSER>
  <COMPOSER>Victor Willis</COMPOSER>
  <PRODUCER>Jacques Morali</PRODUCER>
  <PUBLISHER>PolyGram Records</PUBLISHER>
  <YEAR>1978</YEAR>
  <ARTIST>Village People</ARTIST>  
</SONG>

A Schema for a Document that Uses the Default Namespace

<xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema"
  xmlns="http://ibiblio.org/xml/namespace/song"
  targetNamespace="http://ibiblio.org/xml/namespace/song"
  elementFormDefault="qualified"
  attributeFormDefault="unqualified"
>
 
  <xsd:element name="SONG" type="SongType"/>

  <xsd:complexType name="SongType">
    <xsd:sequence>
      <xsd:element name="TITLE" type="xsd:string"/>
      <xsd:element name="PHOTO" type="PhotoType"  
        minOccurs="0"/>
      <xsd:element name="COMPOSER"  type="xsd:string" 
        maxOccurs="unbounded"/>
      <xsd:element name="PRODUCER"  type="xsd:string" 
        minOccurs="0" maxOccurs="unbounded"/>
      <xsd:element name="PUBLISHER" type="xsd:string" 
        minOccurs="0"/>    
      <xsd:element name="YEAR" type="xsd:gYear"/>
      <xsd:element name="ARTIST" type="xsd:string" 
        minOccurs="0" maxOccurs="unbounded"/>
    </xsd:sequence>
  </xsd:complexType>

  <xsd:complexType name="PhotoType">
    <xsd:complexContent>
       <xsd:restriction base="xsd:anyType">
         <xsd:attribute name="ALT"    type="xsd:string"/>
         <xsd:attribute name="WIDTH"  type="xsd:nonNegativeInteger"/>
         <xsd:attribute name="HEIGHT" type="xsd:nonNegativeInteger"/> 
      </xsd:restriction>
    </xsd:complexContent>
  </xsd:complexType>
  
</xsd:schema>

Reversing the Default Namespace

<schema xmlns="http://www.w3.org/2001/XMLSchema"
  xmlns:song="http://ibiblio.org/xml/namespace/song"
  targetNamespace="http://ibiblio.org/xml/namespace/song"
  elementFormDefault="qualified"
  attributeFormDefault="unqualified"
>
 
  <element name="song:SONG" type="song:SongType"/>

  <complexType name="song:SongType">
    <sequence>
      <element name="song:TITLE" type="string"/>
      <element name="song:PHOTO" type="song:PhotoType"  
        minOccurs="0"/>
      <element name="song:COMPOSER"  type="string" 
        maxOccurs="unbounded"/>
      <element name="song:PRODUCER"  type="string" 
        minOccurs="0" maxOccurs="unbounded"/>
      <element name="song:PUBLISHER" type="string" 
        minOccurs="0"/>    
      <element name="song:YEAR" type="gYear"/>
      <element name="song:ARTIST" type="string" 
        minOccurs="0" maxOccurs="unbounded"/>
    </sequence>
  </complexType>

  <complexType name="song:PhotoType">
    <complexContent>
       <restriction base="anyType">
         <attribute name="ALT"    type="string"/>
         <attribute name="WIDTH"  type="nonNegativeInteger"/>
         <attribute name="HEIGHT" type="nonNegativeInteger"/> 
      </restriction>
    </complexContent>
  </complexType>
  
</schema>

Multiple Namespaces, Multiple Schemas

<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<SONG xmlns="http://ibiblio.org/xml/namespace/song"
      xmlns:xlink="http://www.w3.org/1999/xlink"
      xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
      xsi:schemaLocation = 
       "http://ibiblio.org/xml/namespace/song xlink_song.xsd
        http://www.w3.org/1999/xlink xlink.xsd"
>
  <TITLE>Hot Cop</TITLE>
  <PHOTO xlink:type="simple" xlink:href="hotcop.jpg"
         xlink:actuate="onLoad" xlink:show="embed"
    ALT="Victor Willis in Cop Outfit" WIDTH="100" HEIGHT="200"/>
  <COMPOSER>Jacques Morali</COMPOSER>
  <COMPOSER>Henri Belolo</COMPOSER>
  <COMPOSER>Victor Willis</COMPOSER>
  <PRODUCER>Jacques Morali</PRODUCER>
  <PUBLISHER>PolyGram Records</PUBLISHER>
  <YEAR>1978</YEAR>
  <ARTIST>Village People</ARTIST>  
</SONG>

XLink Schema

<?xml version="1.0"?>
<xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema"
  xmlns="http://www.w3.org/1999/xlink"
  targetNamespace="http://www.w3.org/1999/xlink"
>

  <xsd:attribute name="type" type="xsd:string" 
                 fixed="simple" />
  <xsd:attribute name="href" type="xsd:anyURI" />
  <xsd:attribute name="actuate" type="xsd:string"
                 fixed="onLoad" />
  <xsd:attribute name="show" type="xsd:string"
                 fixed="embed" />

</xsd:schema>

Song Schema with XLink Support

<?xml version="1.0"?>
<xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema"
  xmlns="http://ibiblio.org/xml/namespace/song"
  xmlns:xlink="http://www.w3.org/1999/xlink"
  targetNamespace="http://ibiblio.org/xml/namespace/song"
  elementFormDefault="qualified"
  attributeFormDefault="unqualified"
>

  <xsd:import namespace="http://www.w3.org/1999/xlink"
              schemaLocation="xlink.xsd"/>

  <xsd:element name="SONG" type="SongType"/>

  <xsd:complexType name="PhotoType">
    <xsd:attribute name="WIDTH"  type="xsd:positiveInteger"
                   use="required" />
    <xsd:attribute name="HEIGHT" type="xsd:positiveInteger"
                   use="required" />
    <xsd:attribute name="ALT"    type="xsd:string"
                   use="required" />
    <xsd:attribute ref="xlink:type"/>
    <xsd:attribute ref="xlink:href" use="required"/>
    <xsd:attribute ref="xlink:actuate"/>
    <xsd:attribute ref="xlink:show"/>                 
  </xsd:complexType>

  <xsd:complexType name="SongType">
    <xsd:sequence>
      <xsd:element name="TITLE"     type="xsd:string"/>
      <xsd:element name="PHOTO"     type="PhotoType"/>
      <xsd:element name="COMPOSER"  type="xsd:string"
                   maxOccurs="unbounded"/>
      <xsd:element name="PRODUCER"  type="xsd:string"
                   minOccurs="0" maxOccurs="unbounded"/>
      <xsd:element name="PUBLISHER" type="xsd:string"
                   minOccurs="0"/>
      <xsd:element name="YEAR"      type="xsd:gYear"/>
      <xsd:element name="ARTIST"    type="xsd:string"
                   maxOccurs="unbounded"/>
    </xsd:sequence>
  </xsd:complexType>

</xsd:schema>

elementFormDefault and elementFormDefault

Specifies whether locally declared elements and attributes are namespace qualified

In a schema, a locally declared element is an element declared directly inside a complexType (not by reference)

<complexType name="CarType">
  <sequence>
    <element name="steering_wheel" type="SteeringWheelType"/>
    <element name="wheel" type="WheelType"/>
  </sequence>
</complexType>

In an instance document, this is a locally declared element:

<vg:car xmlns:vg="http://www.vg.org/autos/" 
  width="12cm" height="10cm">
    <steering_wheel diameter="24cm" />
    <wheel number="4" />
</vg:car>

Does not apply to globally declared items
Default is unqualified for both elements and attributes. This is correct for attributes but backwards from what it should be for elements.
Always set elementFormDefault to qualified and don't use local elements.

What Goes at the end of a Namespace URI?

The flaw is the conflation of name, location and identity but that flaw is the basic feature by which the WWW runs so we are stuck there. All the handwaving about URN/URI/URL doesn't avoid the simple fact that if one puts http:// anywhere in browser display space, the system colors it blue and puts up a finger.

The monkey expects a resource and when it doesn't get one, it shocks the monkey. Monkeys don't read specs to find out why they should be shocked. They turn red and put up a finger.

--Claude L Bullard on the xml-dev mailing list

The Resource Directory Description Language

An XML application for pages at the end of a namespace URI.
Invented by Jonathan Borden, Tim Bray, and others on the xml-dev mailing list
A Resource Directory provides a text description of some class of resources and of other resources related to that class. It also contains a directory of links to these related resources.
An XML namespace is one possible kind of resource. Related resources might include schemas, stylesheets, Java content handlers, browser plug-ins, and more.
The RDDL DTD is an extension of XHTML Basic 1.0 using XHTML Modularization.
RDDL adds one new element to XHTML Basic 1.0: resource.

The resource Element

The resource element is in the http://www.rddl.org/ namespace.
The rddl prefix is customary.
The rddl:resource element is a simple XLink; that is, it has an xlink:type="simple" attribute
The rddl:resource element can be placed anywhere in HTML where a p element may appear.
The rddl:resource can contain may of the XHTML Basic elements (headings, paragraphs, lists, hyperlinks, forms, tables, images, meta information ) that the body element may contain.
The content of the rddl:resource element should describe the associated resource.
Resource elements can contain other resource elements.

Example RDDL resource Elements

For the http://www.cafeconleche.org/baseball/ namespace:

<rddl:resource xlink:href="baseball.css" 
    xlink:role="http://www.rddl.org/arcrole.htm#CSS">
  <div id="CSS" class="resource">
    <h3>CSS Stylesheet</h3>
    <p>A <a href="baseball.css">CSS stylesheet</a> 
    for baseball statistics documents.</p> 
  </div>
</rddl:resource>

<rddl:resource xlink:href="baseball.dtd"
    xlink:role="http://www.rddl.org/arcrole.htm#DTD">
  <div id="DTD" class="resource">
    <h3>DTD</h3>
    <p>A <a href="baseball.dtd">DTD</a> for , 
    baseball statistics</p>
  </div>
</rddl:resource>

An Example RDDL Document

<!DOCTYPE html PUBLIC "-//XML-DEV//DTD XHTML RDDL 1.0//EN" 
                      "http://www.openhealth.org/RDDL/rddl-xhtml.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" 
      xmlns:xlink="http://www.w3.org/1999/xlink"
      xmlns:rddl="http://www.rddl.org/">
<head>
<title>RDDL Resources for Baseball Statistics</title>
</head>
<body>
<h1>RDDL Resources for Baseball Statistics</h1>

<p>This is a sample RDDL document 
used in Elliotte Rusty Harold's seminars
including</p>

<ul>
  <li>XLinks and XPointers</li>
  <li>Namespaces in XML</li>
</ul>

<p>It describes resources related to
the baseball statistics DTD developed in the XML
Bible and located at the namespace 
<code>http://www.cafeconleche.org/baseball/</code>.</p>

<p>
<img src="../smallbiblecover.jpg" width="127" height='156'
  alt="Cover of the XMl Bible"/>
</p>

<rddl:resource xlink:href="baseball.css" 
    xlink:role="http://www.rddl.org/arcrole.htm#CSS">
  <div id="CSS" class="resource">
    <h3>CSS Stylesheet</h3>
    <p>A <a href="baseball.css">CSS stylesheet</a> 
    for baseball statistics documents.</p> 
  </div>
</rddl:resource>

<rddl:resource xlink:href="baseball.dtd"
    xlink:role="http://www.rddl.org/arcrole.htm#DTD">
  <div id="DTD" class="resource">
    <h3>DTD</h3>
    <p>A <a href="baseball.dtd">DTD</a> for , 
    baseball statistics</p>
  </div>
</rddl:resource>

<p>
Copyright 2001 <a href="http://www.macfaq.com/personal.html">Elliotte Rusty Harold</a><br class="empty"/>
<a href="mailto:elharo@metalab.unc.edu">elharo@metalab.unc.edu</a><br class="empty"/>
Last Modified Sunday, January 14, 2001
</p>

</body>
</html>

View in Browser

The xlink:href attribute

Contains a URI, possibly relative, pointing to the related resource

The xlink:role attribute

Identifies the type of the related resource with an absolute URI
Can be the namespace URI of the root element:

http://www.w3.org/2000/10/XMLSchema

XML Schema

http://www.rddl.org/arcrole.htm#SOCAT

OASIS Open Catalog

http://www.ascc.net/xml/schematron

Schematron

http://www.xml.gr.jp/xmlns/relaxCore

RELAX schema

http://www.w3.org/2000/01/rdf-schema#

RDF Schema
Can be a MIME media type URI at http://www.isi.edu/in-notes/iana/assignments/media-types/

http://www.isi.edu/in-notes/iana/assignments/media-types/application/pdf

Acrobat PDF version of the document
Can be a spec-defined URI:

http://www.rddl.org/arcrole.htm#DTD

DTD

The xlink:arcrole attribute

For situations where the nature/role alone isn't enough, this offers an additional URI defining the purpose of the link.
Well-known purposes include:

http://www.rddl.org/purposes#validation
This resource should be used for classic XML or SGML DTD validation before the document is parsed.

http://www.rddl.org/purposes#schema-validation
This resource should be used for validation via some sort of schema after the document is parsed.; the The type of schema would normally be identified by the nature.

http://www.rddl.org/purposes#module
A file which that is only part of a complete DTD; and that is typically used in modularized DTDs like such as XHTML 1.1 and SMIL 2.0

http://www.rddl.org/purposes#schema-module
A module used in a schema

http://www.rddl.org/purposes#entities
A DTD fragment containing only entity definitions such as xhtml-special.ent in modular XHTML

http://www.rddl.org/purposes#notations
A DTD fragment containing only notation declarations such as xhtml-notations-1.mod in modular XHTML

http://www.rddl.org/purposes/software#xslt-extension
Software implementing an extension function or element for XSLT

http://www.rddl.org/purposes/software#software-package
A grouping of software resources

http://www.rddl.org/purposes/software#software-project
A collection of resources related to a software package

http://www.rddl.org/purposes#JAR

A zip file with the extension .jar containing Java classes

http://www.rddl.org/purposes/software#reference
Documentation for the resource

http://www.rddl.org/purposes/software#normative-reference
the definitive specification of the resource's syntax and semantics

http://www.rddl.org/purposes/software#non-normative-reference
A useful but non-authoritative description of the resource's syntax and semantics

http://www.rddl.org/purposes#prior-version
Documentation for a previous version of the resource's vocabulary; for example, the XHTML 1.0 specification relative to XHTML 1.1

http://www.rddl.org/purposes#definition
The definition of a term

http://www.rddl.org/purposes#icon
An image that represents the resource

http://www.rddl.org/purposes#directory
Another RDDL document whose resources should be merged with this document's resources

http://www.rddl.org/purposes#alternate
An alternative for a resource with the same nature as this one

The xlink:title attribute

May contain a short, human readable description of the resource as plain, unmarked text.
Should not be used as a substitute for a more complete, HTML-marked-up description of the related resource in the contents of the rddl:resource element.

The xlink:show and xlink:actuate attributes

These two attributes are not used on rddl:resource. They must have the value none.

Declarations for rddl:resource

<!ELEMENT rddl:resource (#PCDATA | %Flow.mix;)*>
<!ATTLIST rddl:resource
          id            ID       #IMPLIED
          xlink:type    (simple) #FIXED "simple"
          xmlns:rddl    CDATA    #FIXED 'http://www.rddl.org/'
          xml:lang      NMTOKEN  #IMPLIED
          xlink:arcrole CDATA    #IMPLIED
          xlink:href    CDATA    #IMPLIED
          xlink:role    CDATA    'http://www.rddl.org/#resource'
          xlink:title   CDATA    #IMPLIED
          xlink:embed   (none)   #FIXED "none"
          xlink:actuate (none)   #FIXED "none"
>

To Learn More

The RDDL Specification: http://www.rddl.org/ (Written in RDDL)

To Learn More

This presentation: http://www.ibiblio.org/xml/slides/sd2001west/namespaces
XML in a Nutshell
- Elliotte Rusty Harold and W. Scott Means
- O'Reilly & Associates, 2001
- ISBN 0-596-00058-8
XML Bible, second edition
- Elliotte Rusty Harold
- Hungry Minds, 2001
- ISBN 0-7645-4760-7

Index | Cafe con Leche