Subject: Re: How to compare two QName values in an XML Schema?
From: Michael Kay <mike@xxxxxxxxxxxx>
Date: Fri, 08 Apr 2011 18:35:12 +0100
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On 08/04/2011 17:00, Costello, Roger L. wrote:
Hi Folks,
Below is an XML Schema, containing two simpleTypes. The second one references the first.
I want an XPath expression that compares the second simpleType's reference to the name of the first simpleType:
/xs:schema/xs:simpleType[1]/@name
eq
/xs:schema/xs:simpleType[2]/xs:restriction/@base
That returns False. I want it to return True.
The @base attribute is defined as an xs:QName, but @name is not. You're
going to have to tell it to build a QName by combining the local name in
@name with the namespace URI in ../@targetNamespace. With a schema-aware
XSLT processor, the best you can achieve is
/xs:schema/xs:simpleType[1]/QName(../@targetNamespace, @name)
eq
/xs:schema/xs:simpleType[2]/xs:restriction/@base
However, running schema-aware code using the schema-for-schemas can be a little mindblowing (and processor-blowing)
Michael Kay
Saxonica
I figured the reason it's returning False is because it is comparing the string "elev:BostonAreaSurfaceElevation" against the string "EarthSurfaceElevation". Yes?
I want it to do a comparison of QNames, not strings. So I type-cast the values:
xs:QName(/xs:schema/xs:simpleType[1]/@name)
eq
xs:QName(/xs:schema/xs:simpleType[2]/xs:restriction/@base)
But that gave me this error:
Casting from xs:unTypedAtomic to xs:QName can never succeed.
Why?
What's the correct way to do the comparison?
---------------------------------------------------------
<xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema"
targetNamespace="http://www.elevation.org"
xmlns:elev="http://www.elevation.org"
elementFormDefault="qualified">
<xsd:simpleType name= "EarthSurfaceElevation">
<xsd:restriction base="xsd:integer">
<xsd:minInclusive value="-1290"/>
<xsd:maxInclusive value="29035"/>
</xsd:restriction>
</xsd:simpleType>
<xsd:simpleType name= "BostonAreaSurfaceElevation">
<xsd:restriction base="elev:EarthSurfaceElevation">
<xsd:minInclusive value="0"/>
<xsd:maxInclusive value="120"/>
</xsd:restriction>
</xsd:simpleType>
</xsd:schema>
---------------------------------------------------------
/Roger
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