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Re: details for checking the "cos-unambig" constraint

From: Henry S. Thompson <ht@cogsci.ed.ac.uk>
Date: 19 Mar 2001 14:05:30 +0000
To: "Weber, Heiko" <Heiko.Weber@softwareag.com>
Cc: "'xmlschema-dev@w3.org'" <xmlschema-dev@w3.org>
Message-ID: <f5bd7bd6ehh.fsf@cogsci.ed.ac.uk>
The XSV implementation uses the approach based on FSMs set out in the
last paragraph of Appendix H [1]:

  "A precise formulation of this constraint can also be offered in
  terms of operations on finite-state automaton: transcribe the
  content model into an automaton in the usual way using epsilon
  transitions for optionality and unbounded maxOccurs, unfolding other
  numeric occurrence ranges and treating the heads of substitution
  groups as if they were choices over all elements in the group, but
  using not element QNames as transition labels, but rather pairs of
  element QNames and positions in the model. Determinise this
  automaton, treating wildcard transitions as opaque. Now replace all
  QName+position transition labels with the element QNames alone. If
  the result has any states with two or more identical-QName-labelled
  transitions from it, or a QName-labelled transition and a wildcard
  transition which subsumes it, or two wildcard transitions whose
  intentional intersection is non-empty, the model does not satisfy
  the Unique Attribution constraint."

ht

[1] http://www.w3.org/TR/xmlschema-1/#non-ambig
-- 
  Henry S. Thompson, HCRC Language Technology Group, University of Edinburgh
          W3C Fellow 1999--2001, part-time member of W3C Team
     2 Buccleuch Place, Edinburgh EH8 9LW, SCOTLAND -- (44) 131 650-4440
	    Fax: (44) 131 650-4587, e-mail: ht@cogsci.ed.ac.uk
		     URL: http://www.ltg.ed.ac.uk/~ht/
Received on Monday, 19 March 2001 09:05:33 GMT

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