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[Bug 6561] Type Substitutable in Restriction

From: <bugzilla@wiggum.w3.org>
Date: Sat, 21 Feb 2009 14:26:59 +0000
To: www-xml-schema-comments@w3.org
Message-Id: <E1Lasol-0005ax-3E@wiggum.w3.org>

Sandy Gao <sandygao@ca.ibm.com> changed:

           What    |Removed                     |Added
             Status|RESOLVED                    |REOPENED
         Resolution|LATER                       |

--- Comment #3 from Sandy Gao <sandygao@ca.ibm.com>  2009-02-21 14:26:57 ---
Some new information to consider.

In section where "context-determined type table" is defined, we have
the following note:

"Note: The constraint Element Declarations Consistent (§  ensures that
even if E ·matches· more than one such declaration D, there will be just one
·context-determined type table·."

If we jump to EDC in, you can see that bullet 2.1 only considers strict
and lax wildcards.

So now we have a contradiction: EDC doesn't guarantee consistency for type
tables when skip wildcards are involved, but CDTT definition depends on that.

Somewhat repeating what was said earlier: the whole 1.0 spec and the rest of
1.1 spec were written with the view that if an element/attribute information
itme matches a "skip" wildcard, then no additional constraints are imposed on
top of "well-formed XML". Why should CDTT be treated differently?

Whether we make this "skip" change or not, consider:

<schema ...>
  <element name="table" type="htmlTable">
    <alternative .../>
    <alternative .../>

  <complexType ...>
      <element name="table" type="furnitureTable"/>

It's almost guaranteed that the complex type would not have a valid instance,
because we will apply the type table from the global element declaration to
instances of the local one.

This seems to limit the usefulness of type alternatives.

Note that in complex type restriction, we made derivation from xs:anyType
magical (clause 2.1 in "Derivation Valid (Restriction, Complex)"). To be
consistent with that, maybe anyType really shouldn't provide any CDTT as
suggested by the original bug report? (CDTT is only used in complex type

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Received on Saturday, 21 February 2009 14:27:09 UTC

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