[Bug 3724] Rule "Content type restricts" needs clarification

http://www.w3.org/Bugs/Public/show_bug.cgi?id=3724

           Summary: Rule "Content type restricts" needs clarification
           Product: XML Schema
           Version: 1.1 only
          Platform: Macintosh
        OS/Version: All
            Status: NEW
          Severity: normal
          Priority: P2
         Component: Structures: XSD Part 1
        AssignedTo: cmsmcq@w3.org
        ReportedBy: cmsmcq@w3.org
         QAContact: www-xml-schema-comments@w3.org


The constraint "Content type restricts" reads in part:

    1 If BCT's {variety} is empty, then either there is no 
      sequence of element information items which is ·locally 
      valid· with respect to RCT's {particle}, or only the 
      empty sequence is.

This seems to assume that RCT has a particle, which is not
true if RCT has {variety} of 'empty' or 'simple'.

The only part of the spec that depends on this constraint
is Schema Component Constraint: Derivation Valid (Restriction, 
Complex), and the thicket of conditionals there is too thick 
for me to tell whether any actual harm results from leaving
"Content type restricts" undefined for various cases.  

I think the 'Content type restricts' rule would be more
useful if it provided a predicate which is true or false for
any pair of content types, instead of providing one which
is true for some, false for some, and undefined for some.
Making this definition more general might also make possible
a simplification of "Derivation Valid (Restriction, Complex)".

Received on Wednesday, 13 September 2006 20:10:16 UTC