Xml schema element with attribute and optional simple content?

[Gazza]

I want to define an element type which has child elements which will
have an attribute, but I want the presence of content for these child
elements (which will be simple when present) to be optional. My type is
defined as such

<xsd:complexTyp e name="DistanceS tructure">
<xsd:sequence >
<xsd:element name="Value">
<xsd:complexTyp e>
<xsd:simpleCont ent>
<xsd:extensio n base="xsd:decim al">
<xsd:attribut e name="Comment" type="xsd:strin g"/>
</xsd:extension>
</xsd:simpleConte nt>
</xsd:complexType >
</xsd:element>
<xsd:element name="Unit">
<xsd:complexTyp e>
<xsd:simpleCont ent>
<xsd:extensio n base="esdalcomm :DistanceUnitTy pe">
<xsd:attribut e name="Comment" type="xsd:strin g"/>
</xsd:extension>
</xsd:simpleConte nt>
</xsd:complexType >
</xsd:element>
</xsd:sequence>
</xsd:complexType >
This definition allows validation of the following when it appears in
my instance document


<StructureLengt h>
<Value Comment="STRUCT URE LENGTH COMMENT">1.1</Value>
<Unit Comment="STRUCT URE LENGTH COMMENT">metre</Unit>
</StructureLength >

But the following does not validate

<StructureLengt h>
<Value Comment="STRUCT URE LENGTH COMMENT"/>
<Unit Comment="STRUCT URE LENGTH COMMENT"/>
</StructureLength >



I need both to be valid possiblilies in my instance document. What can
I do?

[Henry S. Thompson]

Re: Xml schema element with attribute and optional simple content?

Gazza writes:
[color=blue]
> <xsd:element name="Value">
> <xsd:complexTyp e>
> <xsd:simpleCont ent>
> <xsd:extensio n base="xsd:decim al">
> <xsd:attribut e name="Comment" type="xsd:strin g"/>
> </xsd:extension>
> </xsd:simpleConte nt>
> </xsd:complexType >
> </xsd:element>[/color]
[color=blue]
> <Value Comment="STRUCT URE LENGTH COMMENT">1.1</Value>[/color]
[color=blue]
> <Value Comment="STRUCT URE LENGTH COMMENT"/>[/color]

The empty string is not a valid xs:decimal, so you should define a union
of the empty string (xs:string restricted to length 0, or xs:string
restricted to an enumeration of only "") and xs:decimal, and use that
instead of xs:decimal itself.

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