- From: Michael Kay <mhk@mhk.me.uk>
- Date: Tue, 13 Jul 2004 23:09:21 +0100
- To: "'Keith Suderman'" <suderman@cs.vassar.edu>, <xmlschema-dev@w3.org>
FWIW, Saxon 8.0 also accepts this schema as valid.
When you get into boundary cases, taking a majority vote of what products do
is not very good evidence of what the spec says (or intended to say). But
the spec seems to go out of its way to say that maxOccurs="0" is legal
almost everywhere, so I can't quite see why the issue is in doubt.
Michael Kay
> -----Original Message-----
> From: xmlschema-dev-request@w3.org
> [mailto:xmlschema-dev-request@w3.org] On Behalf Of Keith Suderman
> Sent: 13 July 2004 22:23
> To: xmlschema-dev@w3.org
> Subject: [xmlschema-dev] <none>
>
> Hello,
>
> I asked a similar question earlier, but I would like
> clarification since I
> didn't make it clear earlier that I wanted to restrict xs:anyType.
>
> Is the following schema valid?
>
> <?xml version="1.0" encoding="UTF-8"?>
> <xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"
> elementFormDefault="qualified" attributeFormDefault="unqualified">
> <xs:element name="root" type="empty"/>
>
> <xs:complexType name="empty">
> <xs:complexContent>
> <xs:restriction base="xs:anyType">
> <xs:sequence>
> <xs:any minOccurs="0"
> maxOccurs="0" processContents="lax"/>
> </xs:sequence>
> </xs:restriction>
> </xs:complexContent>
> </xs:complexType>
> </xs:schema>
>
>
> XSV 2.5, XML Spy, and Xerces-J 2.6.2 all accept this schema
> as valid, but
> Xerces-C 2.5 reports an error claiming that maxOccurs=0 is
> illegal. When
> this was pointed out on the xerces-c list the folks there seemed
> unconvinced and replied:
>
> >'the derivation by restriction has some constraints, for
> some reference,
> >please see the following table:
> >http://www.w3.org/TR/xmlschema-0/#restrictsTable and
>
> >http://www.w3.org/TR/xmlschema-1/#section-Built-in-Complex-Ty
> pe-Definition
> >You'll see that anyType has { minOccurs, maxOccurs } as {
> 1, 1 } which
> >can't be restricted.'
>
> As I understand it, the restrictsTable referred to above
> (which has been
> amended in an errata [1]) only "shows several examples" of
> how element
> definitions may be restricted, it's not an exhaustive list of what is
> allowed. Also, case 5.3 of [2] says "the particle of the
> complex type
> definition itself must be a .valid restriction. of the
> particle of the
> {content type} of the {base type definition}". In the built
> in complex
> type definition [3] the {particle} of the {content type} is a
> sequence with
> {minOccurs, maxOccurs} = {0, unbounded}, which can be
> restricted to {0, 0}.
> However, I'm unlikely to convince anyone on the Xerces-C list
> that the
> above schema is correct (or that everyone else is wrong)
> without some sort
> of confirmation from this list.
>
> Finally, is
>
> <xs:complexType name="empty"/>
>
> equivalent (in the sense that <root/> is the only valid
> document) to the
> definition above?
>
> Thanks in advance,
> Keith
>
> References
>
> [1] http://www.w3.org/2001/05/xmlschema-errata.html#e0-20
> [2] http://www.w3.org/TR/xmlschema-1/#derivation-ok-restriction
> [3]
> http://www.w3.org/TR/xmlschema-1/#section-Built-in-Complex-Typ
> e-Definition
>
>
> --------------------------------------------------
> Keith Suderman
> Technical Specialist
> American National Corpus
> suderman@cs.vassar.edu
> http://americannationalcorpus.org
>
>
Received on Wednesday, 14 July 2004 08:35:12 UTC