RE: [xml-dev] xpath problem

["Michael Kay" <mike@saxonica.com>]

>The referenced "a" node should exist in its preceding-siblings, the
preceding-siblings of its parent, ... up to the "x" ascendant: 

Apart from stopping at the x element, that constraint can be written

@id-ref = ancestor-or-self::*/preceding-sibling::*/@id

Stopping at the x element can be done as

@id-ref = (ancestor-or-self::* except
ancestor::x/ancestor-or-self::*)/preceding-sibling::*/@id


Regards,

Michael Kay
http://www.saxonica.com/
http://twitter.com/michaelhkay 

> -----Original Message-----
> From: Vincent De Groote [mailto:list.encelade@gmail.com] 
> Sent: 12 January 2010 17:09
> To: xml-dev
> Subject: [xml-dev] xpath problem
> 
> Hello,
> 
> I have a xml file, simplified like this:
> 
> <a-file>
> 
> <x>
>   <a id='a1'/>
>   <a id='a2'/>
>   <bb>
>     <xx>
>        <a id='55'/>
>        <a id='66'/>
>     </xx>
>     <a id='a3'/>
>     <a id='a4'/>
>     <cc>
>        <a-ref id-ref='a2'/>
>        <a-ref id-ref='a4'/>
>     </cc>
>   </bb>
>   <a id='a7'/>
>   <a id='a8'/>
> </x>
> 
> <x>
>   ...
> </x>
> 
> </a-file>
> 
> In this xml file, "a-ref/@id-ref" shoud reference a "a/@id" 
> under its "x" ascendant.
> 
> I wrote the xml schema grammar: the "a/@id" attributes are 
> checked to be unique within an "x" element, and the 
> "a-ref/@id-ref" attributes are checked to reference an 
> existing "a/@id" attribute.
> 
> I have another constraint:  an "a-ref/@id-ref" may only 
> reference a "a/@id" node which appears before him, within its 
> "x" ascendant.
> The referenced "a" node should exist in its 
> preceding-siblings, the preceding-siblings of its parent, ... 
> up to the "x" ascendant:
> 
> In other words, in the example, the first "a-ref" element 
> should only reference one of the following ids: a1, a2, a3, 
> a4, but not 55 or 66,
> a7 or a8.
> 
> In xslt-2, i can write a function which checks this rule, but 
> i cannot find a way to write it in a grammar.
> I will need to use embedded shematron rules for other checks, 
> but i cannot find an xpath to check this rule.
> 
> I'm working with saxon9-ee edition.
> 
> Any idea on how to do that ?
> 
> Thanks for your replies
> Vincent De Groote
> 
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