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Posted to j-users@xerces.apache.org by Jeff Greif <jg...@alumni.princeton.edu> on 2010/09/18 07:35:46 UTC
Representation of complex types derived by extension
When using the Xerces 2.8.1 XML Schema API, the derived type from this
schema:
<?xml version="1.0" ?>
<schema xmlns="http://www.w3.org/2001/XMLSchema"
targetNamespace="urn:webalo:try-extension"
xmlns:tns="urn:webalo:try-extension">
<element name="root" type="tns:Derived"/>
<complexType name="Base">
<sequence>
<element name="a" type="string"/>
<element name="b" type="string"/>
</sequence>
</complexType>
<complexType name="Derived">
<complexContent>
<extension base="tns:Base">
<sequence>
<element name="c" type="string"/>
<element name="d" type="string"/>
<element name="e" type="string"/>
</sequence>
</extension>
</complexContent>
</complexType>
</schema>
is represented in that API as though it had content model:
<complexType name="Derived">
<sequence>
<sequence>
<element name="a" type="string"/>
<element name="b" type="string"/>
</sequence>
<sequence>
<element name="c" type="string"/>
<element name="d" type="string"/>
<element name="e" type="string"/>
</sequence>
</sequence>
</complexType>
rather than what I would have naively thought:
<complexType name="Derived">
<sequence>
<element name="a" type="string"/>
<element name="b" type="string"/>
<element name="c" type="string"/>
<element name="d" type="string"/>
<element name="e" type="string"/>
</sequence>
</complexType>
That is, the XSModelGroup representing the content of the type has two
particles, each of which has a term which is an XSModelGroup, one with
two and one with three particles.
I have a test program to demonstrate this, if it is needed.
Is this expected behavior and is it documented somewhere?
What I've found elsewhere includes:
a. "A complex type which extends another does so by having additional
content model particles at the end of the other definition's content
model, or by having additional attribute declarations, or both."
from XML Schema 1.0 Second Edition, section 2.2.1.3, which seems to
suggest the form I had expected.
b. On the other hand, the infoset description, 3.4.1 which suggests
there is a separate "base type definition" and "content type" which
contains a content model, which could suggest the nested form found in
my test.
c. The documentation for the XSComplexTypeDefinition.getParticle()
method refers to "A particle for a mixed or element-only content model...".
Thanks for any illumination.
Jeff
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Re: Representation of complex types derived by extension
Posted by Michael Glavassevich <mr...@ca.ibm.com>.
Hi Jeff,
What you are getting from the XSModel is consistent with the definition of
the {content type} in the XML Schema 1.0 spec. For an extension it's a
sequence of two particles; a particle for the base content followed by a
particle containing the effective content [1] from the extension. Below the
anchor [1] you'll see the formal definition in 3.2.3.
Thanks.
[1] http://www.w3.org/TR/2004/REC-xmlschema-1-20041028/#key-exg
Michael Glavassevich
XML Parser Development
IBM Toronto Lab
E-mail: mrglavas@ca.ibm.com
E-mail: mrglavas@apache.org
Jeff Greif <je...@gmail.com> wrote on 09/18/2010 01:35:46 AM:
> When using the Xerces 2.8.1 XML Schema API, the derived type from this
> schema:
>
> <?xml version="1.0" ?>
> <schema xmlns="http://www.w3.org/2001/XMLSchema"
> targetNamespace="urn:webalo:try-extension"
> xmlns:tns="urn:webalo:try-extension">
>
> <element name="root" type="tns:Derived"/>
>
> <complexType name="Base">
> <sequence>
> <element name="a" type="string"/>
> <element name="b" type="string"/>
> </sequence>
> </complexType>
>
> <complexType name="Derived">
> <complexContent>
> <extension base="tns:Base">
> <sequence>
> <element name="c" type="string"/>
> <element name="d" type="string"/>
> <element name="e" type="string"/>
> </sequence>
> </extension>
> </complexContent>
> </complexType>
> </schema>
>
> is represented in that API as though it had content model:
>
> <complexType name="Derived">
> <sequence>
> <sequence>
> <element name="a" type="string"/>
> <element name="b" type="string"/>
> </sequence>
> <sequence>
> <element name="c" type="string"/>
> <element name="d" type="string"/>
> <element name="e" type="string"/>
> </sequence>
> </sequence>
> </complexType>
>
> rather than what I would have naively thought:
>
> <complexType name="Derived">
> <sequence>
> <element name="a" type="string"/>
> <element name="b" type="string"/>
> <element name="c" type="string"/>
> <element name="d" type="string"/>
> <element name="e" type="string"/>
> </sequence>
> </complexType>
>
> That is, the XSModelGroup representing the content of the type has two
> particles, each of which has a term which is an XSModelGroup, one with
> two and one with three particles.
>
> I have a test program to demonstrate this, if it is needed.
>
> Is this expected behavior and is it documented somewhere?
>
> What I've found elsewhere includes:
>
> a. "A complex type which extends another does so by having additional
> content model particles at the end of the other definition's content
> model, or by having additional attribute declarations, or both."
>
> from XML Schema 1.0 Second Edition, section 2.2.1.3, which seems to
> suggest the form I had expected.
>
> b. On the other hand, the infoset description, 3.4.1 which suggests
> there is a separate "base type definition" and "content type" which
> contains a content model, which could suggest the nested form found in
> my test.
>
> c. The documentation for the XSComplexTypeDefinition.getParticle()
> method refers to "A particle for a mixed or element-only content
model...".
>
> Thanks for any illumination.
>
> Jeff
>
>
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