RE: [xml-dev] How to Unique contraint

["Priscilla Walmsley" <pwalmsley-lists@datypic.com>]

Hi,

It's not valid because the field xpath is only allowed to return zero or one
node relative to the selector xpath, and in this case it would return two.
(Validation Rule: Identity-constraint Satisfied, part #3) [1].

I can't think of a way to do this with the XML you've got, but if you
changed the attributes into child elements, as in:

  <anElement>
    <port>123</port>
    <debug-port>aaa</debug-port>
  </anElement>
  <anElement>
    <port>abc</port>
    <debug-port>123</debug-port>
  </anElement>

you could use:

    <xs:unique name="port">
      <xs:selector xpath="anElement/port|anElement/debug-port"/>
      <xs:field xpath="."/>
    </xs:unique>

(You can't use anElement/@port|anElement/@debug-port in the selector because
you are not allowed to use the attribute axis in the selector.)


Hope that (sort of) helps,
Priscilla

------------------------------------
Priscilla Walmsley
Author, Definitive XML Schema
http://www.datypic.com
------------------------------------

[1] http://www.w3.org/TR/xmlschema-1/#cvc-identity-constraint


> -----Original Message-----
> From: Michael Kay [mailto:mike@saxonica.com] 
> Sent: Wednesday, March 21, 2007 2:11 PM
> To: smcardle@spansurf.com; xml-dev@lists.xml.org
> Subject: RE: [xml-dev] How to Unique contraint
> 
> > 
> > Does anybody know how to do this so it looks something like 
> > the following INVALID constraint, but I hope you get the picture.
> > 
> > <xs:unique name="port">
> > 	<xs:selector xpath="anElement"/>
> > 	<xs:field xpath="@debug-port | @port"/> </xs:unique>
> > 
> 
> What makes you think this constraint is invalid? It looks OK to me.
> 
> Michael Kay
> http://www.saxonica.com/
> 
> 
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