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At 06:51 PM 7/2/2002 -0400, Betty Harvey wrote:
>I haven't been following the progress of XQuery closely. I was advised
>today that a W3C Schema had to be developed instead of a DTD because
>XQuery only works with Schema.
XQuery works with well-formed documents, DTD-governed documents, or XML
Schema-governed documents. I think the following quote from the Data Model
draft is clear and straightforward on this subject:
From http://www.w3.org/TR/query-datamodel/#psv:
>3.3 XML Schemas and the XML Information Set
>
>The data model supports the following classes of XML documents:
>
>1. Schema-validated documents, i.e., those validated with respect to a
>schema,
>
>2. DTD-valid documents, i.e., those documents validated with respect
>to a DTD, and
>
>3. Well-formed documents with no corresponding DTD or schema.
The mappings from DTDs and well-formed documents to the equivalent schema
documents are not yet finished, as editorial notes in the Data Model
document point out.
As you note, XQuery does not define a mapping for RELAX-NG. This is also an
issue for relational data, object data, or any other kind of typed data
that is not actually an XML file governed by a schema. To make XQuery work
for these data sources, you must define a mapping, either to the PSVI or
directly to the XML Query and XPath Data Model. For relational sources,
this is done by SQL/XML, a specification being developed by ISO/ANSI [1],
which defines the mapping in terms of equivalent XML schemas and documents.
To my knowledge, nobody has done this for RELAX-NG. Anybody who wants to do
such a mapping will need to think about how to match the purely structural
typing of RELAX-NG to the named typing used in XQuery.
Jonathan
[1] Relevant SQL/XML specs:
The XML Data type and Publishing Functions:
ftp://SQLStandards.org/SC32/National_Bodies/USA_NCITS_H2/2002docs/H2-2002-020r1.pdf
Table Mapping:
ftp://SQLStandards.org/SC32/National_Bodies/USA_NCITS_H2/2001docs/H2-2001-373r1.pdf
Mapping non-predefined data types:
ftp://SQLStandards.org/SC32/National_Bodies/USA_NCITS_H2/2002docs/H2-2002-018.pdf
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