<!entity % xref " label|ref|pageref|cite|url|htmlurl|ncite " >
As soon as it´s a little bit more sophisticated a document will need references to other places within the document.
<!element label - o empty> <!attlist label id cdata #required>
A example could look like:
<sect1>Welcome to the article<label id="intro"> <p>...
<!element ref - o empty> <!attlist ref id cdata #required name cdata "<@@refnam>">
With this tag you can refer to a place within your document labeled as in Label Tag.
The way the reference is mapped in you document again depends to the mapper. May result to a hyper-ref (HTML) or a section number (LaTeX).
<!element pageref - o empty> <!attlist pageref id cdata #required>
A example for a pageref:
In the HTML mapping there is no use for pageref, because there are no page numbers. In LaTeX mapping the tag is mapped to the pagenumber of the reffered label.
<!element url - o empty> <!attlist url url cdata #required name cdata "<@@urlnam>" >
A example for a url:
<url url="http://www.gnu.org" name="GNU Organization">
The mapping to html brings up a hyper-ref in your document. The reference is the value of the url attribute, the text standing in the Hyperref is the name attribute's value.
In LaTeX mapping this one results to the name followed by the url.
<!element htmlurl - o empty> <!attlist htmlurl url cdata #required name cdata "<@@urlnam>" >
<htmlurl url="http://www.gnu.org" name="GNU Organization">
The only difference between this tag and the Url Tag is in the LaTeX mapping.
The LaTeX mapping simply drops the url attribute and emphasizes the name.
In all other cases it's absolutely the same as the url tag.
<!element cite - o empty> <!attlist cite id cdata #required>
AFAIK this one need´s bibTeX to work nicely. So I'm terribly sorry, but I was not jet able to make use of it. For that reason for sure I'm the wrong one to explain about it.
<!element ncite - o empty> <!attlist ncite id cdata #required note cdata #required>
Same as Cite Tag.