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Jon.Ellis@Sun.COM wrote:
>Mike Champion <mc@xegesis.org> wrote:
>
>
>>--- Evan Lenz <evan@evanlenz.net> wrote:
>>
>>
>>So why do you think they are bothering to implement
>>only a subset if full compliance is "hardly onerous?"
>>
>>
>
>Makes you wonder doesn't it ;-)
>
>The footprint requirements just don't appear allow it. There are more productions to process the DTD than the XML document, and that's before you have to deal with what you find there.
>
With the advantage of hindsight I think the XML *recommendation* (which
is all it is, after all - not some form of legally binding definition)
erred in requiring too much of XML processors. The problem now is that
many interfaces (especially SAX/SAX2) were designed around the
recommendation requirements and ignored ways of possibly structuring
processing to be more modular. In particular, validation and related
issues could probably be better handled as a layer above the basic
parser rather than as an integrated part of the parser.
With this type of breakdown it'd be sensible to take *all* the DTD
processing out of the parser. All a parser would have to do is report
document type declarations to the application, and make the internal
subset (if present) available as text. If an application wanted to
support DTD processing it could add the appropriate layer on top of the
parser interface (as the equivalent of a SAX filter). The same holds for
validation. This would have avoided all the problems with different
levels of validation support using different parsers - just take the
best parser for your purposes and combine it with the best validator.
This is the approach taken with the XMLPull interface
(http://www.xmlpull.org), though I don't think anyone has built a higher
layer on top of it yet to handle DTD processing and/or validation.
Perhaps something like this should be used as the basis of XML handling
in J2ME, rather than the SAX-based JAXP. That way applications wanting
full XML support would be able to get it by layering, which would not be
possible with the XML-subset JAXP being discussed now (SAX doesn't allow
the necessary information to be reported to a higher layer, and also
doesn't allow a higher layer to define entities for the parser to use).
And yes, I see the subsetting as a good thing. For a growing number of
XML applications DTDs and entity declarations just don't fit (and I say
this as someone who likes DTDs and uses them often in my own work).
Rather than throwing tantrums over this evolutionary change in usage the
XML community would be better off recognizing it and defining an
approved subset, then pressuring other groups (such as the SOAP
community) to use that subset. That way at least there's a chance of
holding the line at *one* standard subset.
- Dennis
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