Proposal Announcement - XML DTDs to XML docs
SimonStL at classic.msn.com
Thu May 21 03:06:29 BST 1998
Paul Prescod wrote:
>> 1) A document syntax specification (a simplified version of well-formed
>> 2) A syntax for linking to DTDs (and perhaps schemas) internal or external
>> (which would depend on XLink)
>> 3) A syntax for DTDs providing rules for validation.
>So at what level do I get the equivalent of internal entities and
>defaulted attributes? And what levels are required of all XML processors
At what level do you get defaulted attributes now? Do you get defaulted
attributes in a well-formed document without a DTD? Right now, it doesn't
look like it. This could be in level 1, if default attributes were deemed
necessary to document syntax, but I'd expect to see it in level 3. Internal
entities could be defined much as they are now, at the start of a document,
within a structure set aside for that purpose using <ENTITY> (or whatever
develops) instead of <!ENTITY>. This would indeed need to be covered in level
1, unless you could live without internal entities. In the past you seemed
quite happy about forcing scripts to be external to a document, so I can't see
why it would be so terrible to exile entities - and DTDs as well - to separate
documents either. I don't think it would be necessary, though, any more than
it's necessary now.
As for requiring levels, level 1 would serve a similar purpose to well-formed
documents today. 2 would be a prerequisite for 3, of course.
>For example: One company's DTD extension could add in SGML tag ommission.
>The start- and end-tag of an element could be implied, without violating
>well-formedness. So then you could use that company's parser through SAX
>and get a completely different set of events than if you used someone
>else's parser. After all, changing the parse is one of the
>responsibilities of the DTD.
I think this is overstating your case rather dramatically. I could do
something similarly brutal by creating a <? shorttags ?> PI at the start of a
regular XML document and using the implied tags. No one else could read my
documents, but I sure could. Not only that, but I already proposed separating
the document syntax - which includes full start- and end-tags - from the DTD.
There's no reason this proposal would allow the DTD to modify the basic
document syntax and markup, period.
>I don't know what you mean by full schema information. DTDs serve as
>schemas (in addition to changing the parse). If you propose to replace
>DTDs, then you are in part designing a new schema language.
We can argue about the meaning of the word schema all you like; it's not that
exciting for me. XML-Data performs similar mapping, but attempts to add a lot
more, parts which I see more as data schemas. If this is a schema, then so be
>is to develop a new schema language *without* changing DTDs. In other
>words, I am suggesting you make your project smaller, not larger. I would
>suggest you forget about entities, defaulted attributes, etc. Leave those
My suggestion is that DTD's present a significant problem in their current
format, and that they could be improved significantly. I would enjoy being
able to focus on elements and attributes, the core of XML (and SGML) document
syntax, and worry less about the rest. This project already is an attempt to
be smaller, but to provide a place for new things to grow.
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