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Re: HELP: XML-Schema - Array and Type Choice?

• From: ht@c... (Henry S. Thompson)
• To: Eddie Robertsson <eddie@a...>
• Date: Tue, 12 Jun 2001 13:28:50 +0100

Eddie Robertsson <eddie@a...> writes:

> Hi,
> 
> Risheng Lin wrote:

<snip/>

> > 2. My second question is about type choice. Below is part of my
> > schema:
> >
> > <xsd:element name="DataValue">
> > <!-- data can be either float or double-->
> > <xsd:complexType>
> >    <xsd:choice>
> >                  <xsd:element name="Data" type="xsd:float"
> > minOccurs="1" maxOccurs="unbounded"/>
> >          <xsd:element name="Data" type="xsd:double" minOccurs="1"
> > maxOccurs="unbounded"/>
> >    </xsd:choice>
> >    <xsd:attribute ref="dataType" use="required" />
> > </xsd:complexType>
> > </xsd:element>
> >
> > But I want more constraints on this schema --- when user supplies the
> > attribute dataType to be "float", the schema will only allow the
> > instance document to supply Data Element to be of type xsd:float; on
> > the other hand, if attribute dataType is "double", the XML document
> > can only supply Data Element of type xsd:double?
> 
> I'm not sure this will work but you can try to create your own datatype
> that is a union between float and double like this:
> 
> <xsd:simpleType name="float_double">
>    <xsd:union memberTypes="xsd:float xsd:double"/>
> </xsd:simpleType>
> 
> Then declare your element Data to be of this type:
> 
> <xsd:element name="Data" type="float_double" minOccurs="1"
> maxOccurs="unbounded"/>
> 
> In your instance document you can then use the xsi:type attribute to
> specify which type you use:
> 
> ...
>    <Data xsi:type="xsd:double">_floatvalue_</Data>
> ...
> 
> However, I'm not sure this will work. The spec says [1]:

<snip/>

It should work.

> I'm not sure if you can just override the evaluation order or if you can
> actually specify the specific type within the union. I.e will the
> validator continue to check the the above example for conformance to the
> xsd:float type if the xsd:double check fails?
> [1] http://www.w3.org/TR/xmlschema-2/#union-datatypes

The spec. should be clearer here -- xsi:type _completely_ overrides
the union--if it's not a double, it's an error, in the above example.

ht
-- 
  Henry S. Thompson, HCRC Language Technology Group, University of Edinburgh
          W3C Fellow 1999--2001, part-time member of W3C Team
     2 Buccleuch Place, Edinburgh EH8 9LW, SCOTLAND -- (44) 131 650-4440
	    Fax: (44) 131 650-4587, e-mail: ht@c...
		     URL: http://www.ltg.ed.ac.uk/~ht/

• References:
  • HELP: XML-Schema - Array and Type Choice?
    • From: Risheng Lin <rlin@e...>
  • Re: HELP: XML-Schema - Array and Type Choice?
    • From: Eddie Robertsson <eddie@a...>

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