W3C home > Mailing lists > Public > public-xml-processing-model-wg@w3.org > June 2008

schema-aware XPath processing in XProc

From: Henry S. Thompson <ht@inf.ed.ac.uk>
Date: Thu, 26 Jun 2008 17:27:11 +0100
To: public-xml-processing-model-wg@w3.org
Message-ID: <f5bod5o17s0.fsf@hildegard.inf.ed.ac.uk>

Hash: SHA1

The good news:  The so-called 'winged horse' _does_ work for us:

 "An unknown schema type might be encountered, for example, if a
  source document has been validated using a schema that was not
  imported into the static context. In this case, an implementation is
  allowed (but is not required) to provide an _implementation-dependent
  mechanism_ for determining whether the unknown schema type is derived
  from the expected schema type. For example, an implementation might
  maintain a data dictionary containing information about type
  hierarchies." [1] [emphasis added]

So XProc implementations can, and I hope will, preserve type hierarchy
information along with the PSVI when they can.

The bad news: XPath processors don't _have_ to do this (I suppose we
could require it. . .), and in any case it doesn't cover substitution
groups :-(

My current inclination: either go ahead and support p:import-schema,
or, at the very least, make a change to the definition of the in-scope
schema definitions in the static context to be implementation-defined,
with the comment "Implementations SHOULD make information from all the
schemas used in upstream schema validation steps available via this
property".  This would essentially mandate support for the winged


[1] http://www.w3.org/TR/xpath20/#id-sequencetype-matching
- -- 
       Henry S. Thompson, School of Informatics, University of Edinburgh
                         Half-time member of W3C Team
      10 Crichton Street, Edinburgh EH8 9AB, SCOTLAND -- (44) 131 650-4440
                Fax: (44) 131 650-4587, e-mail: ht@inf.ed.ac.uk
                       URL: http://www.ltg.ed.ac.uk/~ht/
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Received on Thursday, 26 June 2008 16:27:48 UTC

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