Re: Schemas and entities (was "And the DTD says, "I'm NOT dead yet!!")

[ht@cogsci.ed.ac.uk (Henry S. Thompson)]

Marcus Carr <mrc@allette.com.au> writes:

> Norman Walsh wrote:
> 
> > XML Schemas provide no mechanism for declaring general entities. (This
> > isn't an oversight on the part of the XML Schema WG, it's a consequence
> > of how schema validation is defined. Briefly, schema validation is performed
> > on the information set constructed by parsing the document. But the parser
> > needs to know about entity declarations *while it's parsing* so schema's
> > just occur "too late" in the process to practically declare entities.)
> 
> This implies that if I need to use general entities, I have to
> preprocess my document against a DTD - is that correct? I was
> unaware that schema processing took place at a different point than
> DTD processing - does this impact on anything else? Sorry if this
> has been covered - I was reclining, secure in the misconception that
> aside from the obvious benefits of schemas, the two were roughly
> equivalent.

Schema-aware processing starts when XML parsing finishes.  If the XML
parser concerned is conformant, it will process and implement the
effect of general entity declarations in the internal subset at
least.  If there are attribute declarations in the internal subset, or 
in the external subset and they are processed, this may also affect
what the schema processor sees.

ht
-- 
  Henry S. Thompson, HCRC Language Technology Group, University of Edinburgh
          W3C Fellow 1999--2001, part-time member of W3C Team
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