The xlink:show attribute has three legal values:
replace
new
parsed
Like all attributes in valid documents, the xlink:show attribute must be declared in a <!ATTLIST> declaration for the DTD's link element. For example:
<!ELEMENT WEBSITE (#PCDATA)>
<!ATTLIST WEBSITE
xmlns:xlink CDATA #FIXED "http://www.w3.org/XML/XLink/0.9"
xlink:type CDATA #FIXED "simple"
xlink:href CDATA #REQUIRED
xlink:show (new | replace | parsed) #IMPLIED "replace"
>