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xsd:all limitations [was: LC-16 ( LC-132 ): Allow arbitrary order with occurrence > 1]

From: Eric van der Vlist <vdv@dyomedea.com>
Date: Wed, 18 Oct 2000 10:35:47 +0200
Message-ID: <39ED60E3.EE996BD7@dyomedea.com>
To: www-xml-schema-comments@w3.org
Occurrence <=1 is only one of the limitations of the all particle and
I'd like to submit a real case where we're stuck by these limitations.

In our RSS 1.0 proposal [1] we've described a mechanism to define
"modules" using different namespaces which can add their own elements
within our "core" vocabulary.

Our problem is that we won't we able to define the order in which the
modules will be specified nor the relative order in which they will
appear in the core elements.

If we define the channel element, for instance, as:

<xsd:element name="channel" content="elementOnly">
 <xsd:complexType>
  <xsd:sequence>
   <xsd:element name="title" type="xsd:string"/>
   <xsd:element name="link" type="xsd:uriReference"/>
 .../...
   <xsd:group ref="rss091:inChannel"/>
   <xsd:group ref="dc:dcElements"/>
  </xsd:sequence>
  <xsd:attribute ref="rdf:about"/>
 </xsd:complexType>
</xsd:element>

I am specifying the relative order between the elements from the "dc"
and "rss091" modules which isn't acceptable for us.

The "natural" solution would be to include the 2 module groups in a
xsd:all:

<xsd:element name="channel" content="elementOnly">
 <xsd:complexType>
  <xsd:sequence>
   <xsd:element name="title" type="xsd:string"/>
   <xsd:element name="link" type="xsd:uriReference"/>
 .../...
   <xsd:all>
    <xsd:group ref="rss091:inChannel" minOccurs="0"/>
    <xsd:group ref="dc:dcElements" minOccurs="0"/>
   </xsd:all>
  </xsd:sequence>
  <xsd:attribute ref="rdf:about"/>
 </xsd:complexType>
</xsd:element>

but this isn't possible since xsd:all here would not be a top level
container and wouldn't include individual elements.

Does anyone have any idea of solutions or workarounds for this kind of
situations ?

[1] http://purl.org/rss/1.0/
-- 
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Eric van der Vlist       Dyomedea                    http://dyomedea.com
http://xmlfr.org         http://4xt.org              http://ducotede.com
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Received on Wednesday, 18 October 2000 04:35:16 GMT

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