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[XML-DEV Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message] RE: Schema for XSLT (concerns mixed content, content attribute)
This is actually a bit confusing, but I think I finally have my head around
it (I certainly didn't two days ago).
If one looks at Section 4.3.3 of Part 1, the description of the {content
type} deserialization rules discusses the EXPLICIT PARTICLE that is
introduced as a parent of most complex type content models. To paraphrase,
unless the complexType's content model is a lone all, group, sequence, or
choice, the model is interpreted as if a compositor has been introduced. In
the case of content='mixed', it is a choice compositor marked
minOccurs='0'/maxOccurs='unbounded'.
That stated, I believe (but may be wrong) that the following:
<complexType name='bob' content='mixed' >
<element name='a'/>
<element name='b'/>
<element name='c'/>
</complexType>
is equivalent to:
<complexType name='bob' content='mixed' >
<choice minOccurs='0' maxOccurs='unbounded' >
<element name='a'/>
<element name='b'/>
<element name='c'/>
</choice>
</complexType>
This is pretty much the DTD story. If one really wants the "revolutionary
structured mixed content model" that acts like elementOnly but allows
non-whitespace character data, one would have needed to write this:
<complexType name='bob' content='mixed' >
<sequence minOccurs='m' maxOccurs='n' >
<element name='a'/>
<element name='b'/>
<element name='c'/>
</sequence>
</complexType>
where m and n are the values that match your expectations ;-)
Taking this into account, I believe my original schema for XSLT was using
content='mixed' correctly, although I now see at least one opportunity to
tighten up some constraints.
DB
http://www.develop.com/dbox
> -----Original Message-----
> From: Noah_Mendelsohn@l... [mailto:Noah_Mendelsohn@l...]
> Sent: Wednesday, April 19, 2000 10:12 PM
> To: Box, Don
> Cc: Curt.Arnold@h...; dbox@d...;
> www-xml-schema-comments@w...; xml-dev@x...;
> xml-dev-temp@e...
> Subject: RE: Schema for XSLT (concerns mixed content, content
> attribute)
>
>
> Schemas treats "mixed" differently than DTD's. In schemas, both
> element-only and mixed take a full content model. The only
> difference
> with mixed is that the instance can have character information item
> children before after and in between the elements validated
> by the model.
> So, you have the full power of content models with mixed.
> Also, mixed
> does not imply any defaults for min/maxOccurs. This is NOT
> the DTD model,
> but it can express every constraint allowed by DTD mixed (and more).
>
> --------------------------------------------------------------
> ----------
> Noah Mendelsohn Voice:
> 1-617-693-4036
> Lotus Development Corp. Fax: 1-617-693-8676
> One Rogers Street
> Cambridge, MA 02142
> --------------------------------------------------------------
> ----------
>
>
>
>
>
>
>
> "Box, Don" <dbox@d...>
> Sent by: www-xml-schema-comments-request@w...
> 04/18/00 06:21 PM
>
>
> To: "'Arnold, Curt'" <Curt.Arnold@h...>,
> "'xml-dev@x...'"
> <xml-dev@x...>
> cc: "Box, Don" <dbox@d...>,
> "'www-xml-schema-comments@w...'"
> <www-xml-schema-comments@w...>, "'xml-dev-temp@e...'"
> <xml-dev-temp@e...>, (bcc: Noah Mendelsohn/CAM/Lotus)
> Subject: RE: Schema for XSLT (concerns mixed
> content, content attribute)
>
> > -----Original Message-----
> > From: Arnold, Curt [mailto:Curt.Arnold@h...]
> > Sent: Tuesday, April 18, 2000 2:01 PM
> > To: 'xml-dev@x...'
> > Cc: 'dbox@d...'; 'www-xml-schema-comments@w...';
> > 'xml-dev-temp@e...'
> > Subject: RE: Schema for XSLT (concerns mixed content, content
> > attribute)
> >
> >
> > First, a few comments on Don's schema for XSLT then a
> > discussion about some problems representing XSLT's content
> > model with schema.
> >
> > The derivedBy attribute was not specified on the definition
> > of the copy and message complex types as appears to be
> > required by Schema representation constraint 1.1
>
> Thanks. I thought I caught all of those. It's now fixed.
>
> > The param element reference in the named-template type
> > definition should have a minOccur="0" and a
> > maxOccur="unbounded". As written, a template has to have one
> > and only one param.
>
> My reading of rule 4.3 under the {content type} definition
> (found under
> section 4.3.3) implies that there is an implicit <choice minOccurs='0'
> maxOccurs='unbounded' > particle over the particle children of a
> content=mixed complex type. I'll defer to Henry on this.
>
> > You frequently use type-scoped element definitions. I try to
> > avoid these unless a specific tag-name has a distinct content
> > models in different contexts since it will be difficult if
> > not impossible to
> > generate an equivalent DTD.
>
> Local element and attribute declarations are one of the more powerful
> features of the schema language. I make no apologies for using them.
> Believe
> me, the WG struggled long and hard to get them to where they
> are now. The
> least we can do as a community is use them ;-)
>
> > Second, Schema doesn't seem to have the ability to adequately
> > represent the content model of <xsl:template> or
> > <xsl:for-each>. <xsl:template> content should be zero or
> > more <xsl:param> elements
> > followed by template content.
>
> Yeah, I thought about alternative ways to model that. One way
> would have
> been to use a named model group (that was my first pass btw).
> The problem
> is
> that for mixed content, you can't use sequence constraints. This is a
> problem with older technologies as well.
>
> > <xsl:for-each> content should
> > be zero or more <xsl:sort> elements followed by template content.
>
> Same problem.
>
> > [snip]
>
> I don't know that anyone has the will to add MORE complexity
> to the schema
> language to handle mixed content.
>
> DB
> http://www.develop.com/dbox
>
>
>
>
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