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We have it from unimpeachable authority that the Namespace mechanism isn't
really for "vocabulary combination" (even though the "Motivation" section
of the spec would seem to suggest that it might be). Thus in
http://www.xml.com/pub/a/1999/01/namespaces.html
it is written: "The only reason namespaces exist, once again, is to give
elements and attributes programmer-friendly names that will be unique
across the whole Internet."
Nevertheless, the use of namespaced names raises interesting questions
from the perspective of vocabulary combination. Consider the example from
the article cited above:
<h:html xmlns:xdc="http://www.xml.com/books";
xmlns:h="http://www.w3.org/HTML/1998/html4";>
<h:head><h:title>Book Review</h:title></h:head>
<h:body>
<xdc:bookreview>
<xdc:title>XML: A Primer</xdc:title>
<h:table>
<h:tr align="center">
<h:td>Author</h:td><h:td>Price</h:td>
<h:td>Pages</h:td><h:td>Date</h:td></h:tr>
<h:tr align="left">
<h:td><xdc:author>Simon St. Laurent</xdc:author></h:td>
<h:td><xdc:price>31.98</xdc:price></h:td>
<h:td><xdc:pages>352</xdc:pages></h:td>
<h:td><xdc:date>1998/01</xdc:date></h:td>
</h:tr>
</h:table>
</xdc:bookreview>
</h:body>
</h:html>
Let's suppose I want to reconstruct an "html view" and a "books view" of
this document. One reason for this could be that I have dedicated modules
for the html and books vocabularies (assuming, of course, that a namespace
entitles me to think of a vocabulary), and I would like a parser-level
filter to feed each module separately with only the input it's designed to
handle. Or I have just one module - say for the books vocabulary - and
I'd like to filter out irrelevant junk.
Judging from the intent of the example, I hypothesize that the relevant
views are, for the html-vocabulary:
<html
<body>
XML: A Primer
<table>
<tr align="center">
<td>Author</td><td>Price</td>
<td>Pages</td><td>Date</td></tr>
<tr align="left">
<td>Simon St. Laurent</td>
<td>31.98</td>
<td>352</td>
<td>1998/01</td>
</tr>
</table>
</body>
</html>
and for the books-vocabulary:
<bookreview>
<title>XML: A Primer</title>
<author>Simon St. Laurent</author>
<price>31.98</price>
<pages>352</pages>
<date>1998/01</date>
</bookreview>
If this is acceptable, then my question is: What is the decision procedure
by which a generic parser-level filter could generate these views, if it's
to take namespaced names as a guide?
"It can't be done" is an acceptable answer, btw.
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