Re: [Bug 12184] Circularity in xs:override

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C. M. Sperberg-McQueen writes:

> Then I guess that at some point you will make a proposal to the
> WG that 12184 be re-opened, so we can discuss whether we
> will or won't reopen it.

In this connection, rereading the status quo section 4.2.5 [1], I am
struck by a apparent (?) contradiction between the newly added text,
beginning "If the above definition is naively translated. . ."  (now
the first real Note after the override element tableau) and the _last_
(third) Note after the definition of *target set*, which appears to
_also_ be intended to address to the problem of circular chains of
overrides.

The latter appears to say that only vacuous chains, i.e. those with no
effective overriding children, are allowed.  Whether the crucial part
of the text here is normative or not can only be determined by looking
at the markup -- which reveals that it is not.

So I'm left thinking we have two non-normative statements which give
not (obviously) compatible advice to implementors as to how they are
supposed to implement the joint recursion specifed by *Schema
Representation Constraint: Override Constraints and Semantics* and
*Schema Representation Constraint: Inclusion Constraints and
Semantics*, without risking non-termination on such inputs.

Happy to be proved wrong. . .

ht

[1] http://www.w3.org/XML/Group/2004/06/xmlschema-1/structures.html#override-schema

- -- 
       Henry S. Thompson, School of Informatics, University of Edinburgh
      10 Crichton Street, Edinburgh EH8 9AB, SCOTLAND -- (44) 131 650-4440
                Fax: (44) 131 651-1426, e-mail: ht@inf.ed.ac.uk
                       URL: http://www.ltg.ed.ac.uk/~ht/
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Received on Friday, 11 March 2011 17:48:27 UTC