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Re: Can't get simple key constraint to work

• From: Michael Glavassevich <mrglavas@c...>
• To: karol.zielonko@g...
• Date: Sat, 29 Nov 2008 22:05:18 -0500

"./Outer" doesn't select the "Outer" declared in your schema. This is because the default namespace does not apply to node tests [1] in XPath expressions. You must use prefixes for names which have a namespace. The following should work:

 <?xml version="1.0" encoding="UTF-8" ?>
<xsd:schema targetNamespace="http://TBD-URI" elementFormDefault="qualified"
 attributeFormDefault="unqualified"
xmlns:xsd="http://www.w3.org/2001/XMLSchema"
 xmlns:tns="http://TBD-URI">

 <xsd:element name="MyRoot" type="tns:MyRootType">
    <xsd:key name="OuterNameKey">
       <xsd:selector xpath="./tns:Outer"/>
       <xsd:field xpath="@OuterName"/>
    </xsd:key>
 </xsd:element>

 <xsd:complexType name="MyRootType">
   <xsd:sequence>
      <xsd:element name="Outer" type="tns:OuterType" maxOccurs="unbounded"/>
   </xsd:sequence>
 </xsd:complexType>

 <xsd:complexType name="OuterType">
    <xsd:attribute name="OuterName" type="xsd:string" use="required"/>
 </xsd:complexType>
</xsd:schema>

Thanks.

[1] http://www.w3.org/TR/xpath#node-tests

Michael Glavassevich
XML Parser Development
IBM Toronto Lab
E-mail: mrglavas@c...
E-mail: mrglavas@a...

"Karol Zielonko" <karol.zielonko@g...> wrote on 11/29/2008 07:02:33 PM:

> Hi,
>
> I'm a newbie to XML schema design and am having trouble getting what would
> seem
> to be a painfully simple key constraint to work. I've looked at tutorial
> pages
> on the creation of keys and use of Xpath therein and still no joy.
>
> Here is the stripped down schema, with my futile attempt at a key constraint
> named "OuterNameKey":
>
>  <?xml version="1.0" encoding="UTF-8" ?>
>  <xsd:schema targetNamespace="http://TBD-URI" elementFormDefault="qualified"
>   attributeFormDefault="unqualified"
> xmlns:xsd="http://www.w3.org/2001/XMLSchema"
>   xmlns="http://TBD-URI">
>
>   <xsd:element name="MyRoot" type="MyRootType">
>      <xsd:key name="OuterNameKey">
>         <xsd:selector xpath="./Outer"/>
>         <xsd:field xpath="@OuterName"/>
>      </xsd:key>
>   </xsd:element>
>
>   <xsd:complexType name="MyRootType">
>     <xsd:sequence>
>        <xsd:element name="Outer" type="OuterType" maxOccurs="unbounded"/>
>     </xsd:sequence>
>   </xsd:complexType>
>
>   <xsd:complexType name="OuterType">
>      <xsd:attribute name="OuterName" type="xsd:string" use="required"/>
>   </xsd:complexType>
>  </xsd:schema>
>
> I want the OuterNameKey key constraint to say, "The value of the OuterName
> attribute of the <Outer> element must be unique within the enclosing
> <MyRoot>
> element.".
>
> Here is a test XML file that (as far as I can understand the Xpath / XML key
> tutorials I've seen) should *not* validate because a duplicate value for
> OuterName has been used in two <Outer> elements:
>
>  <?xml version="1.0" encoding="UTF-8"?>
>  <MyRoot xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
>      xsi:schemaLocation="http://TBD-URI Example.xsd" xmlns="http://TBD-URI">
>      <Outer OuterName="Must Be Unique"/>
>      <Outer OuterName="Must Be Unique"/>
>  </MyRoot>
>
> I'm using Oxygen and when I hit validate for the above XML it validates.
>
> Now I *was* able to get the following version of the "OuterNameKey" key
> constraint to catch the error in the XML above. I changed the xpath in
> xsd:selector to "*", that is:
>
>    <xsd:key name="OuterNameKey">
>       <xsd:selector xpath="*"/>
>       <xsd:field xpath="@OuterName"/>
>    </xsd:key>
>
> If the change above is made to the schema then the example XML will not
> validate. Oxygen will say:
>
>  Duplicate key value [Must Be Unique] declared for identity constraint
>  "OuterNameKey" of element "MyRoot".
>
> which is what I want, except I don't want to use this wildcard hack.
>
> So what am I missing?
>
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• References:
  • Can't get simple key constraint to work
    • From: "Karol Zielonko" <karol.zielonko@g...>