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DTDs are parts of documents but schemas are paired with documents

From: Dan Connolly <connolly@w3.org>
Date: Mon, 22 May 2000 08:42:22 -0500
Message-ID: <3929393E.337CDF98@w3.org>
To: www-xml-query-comments@w3.org
I'm still in my first read thru, so I'm not sure how this
impact the rest of the spec, but this looks misleading:

	A well-formed document may have an associated schema, derived
	from one or more XML Schema documents; it may have an
	associated DTD; or it may have no schema, i.e., it is


In XML, a DTD is part of a document. Schemas may be associated
with documents, but they're distinct. In particular,
it's sensible to say "I used document X with schema S1 and
schema S2" where S1 != S2, but it's not sensible to say
"I used document X with DTD D1 and DTD d2" because X's
DTD is part of X. Another way of saying it:
xml-1.0-valid is a one-place predicate over documents;
xml-schema-valid is a two-place predicate over
documents and schemas:

	"An XML document is valid if it has an associated document type
	declaration and if the document complies with the constraints
	expressed in it."

	-- http://www.w3.org/TR/1998/REC-xml-19980210#dt-valid

	"[Definition:]  Throughout this document we use the phrase
	schema-valid loosely to refer to a successful outcome to
	any of the above-listed assessments of an element
	information item with respect to a schema. "


Dan Connolly, W3C http://www.w3.org/People/Connolly/
Received on Monday, 22 May 2000 09:42:42 UTC

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