Re: [xml-dev] Venetian Blinds vs Garden of Eden patterns for industry

["Pete Cordell" <petexmldev@codalogic.com>]

Original Message From: "G. Ken Holman"

>>My XPath knowledge is very weak, but does that allow for matching 'b' in 
>>the 'tree' of:
>>
>>ns1:root/a/b  ?
>
> No, you only asked "b whose qualified parent is in namespace ns1"

Ah sorry.  Instead of 'parent' I should have used the word 'ancestor'.

More precisely what I should have said is that XPath can't express "b whose 
nearest qualified ancestor is in namespace ns1".  Sort of 
b[qualified-ancestor::ns1]!

I will only be too pleased if my statement turns out to be false.

Thanks,

Pete Cordell
Codalogic Ltd
Interface XML to C++ the easy way using C++ XML
data binding to convert XSD schemas to C++ classes.
Visit http://codalogic.com/lmx/ or http://www.xml2cpp.com
for more info

----- Original Message ----- 
From: "G. Ken Holman" <gkholman@CraneSoftwrights.com>
To: "XML-Dev Mailing list" <xml-dev@lists.xml.org>
Sent: Thursday, October 28, 2010 6:40 PM
Subject: Re: [xml-dev] Venetian Blinds vs Garden of Eden patterns for 
industry standards XML Schemas


>
> At 2010-10-28 18:13 +0100, Pete Cordell wrote:
>>Original Message From: "G. Ken Holman"
>>>At 2010-10-28 14:32 +0100, Pete Cordell wrote:
>>>>Hi David,
>>>>
>>>>It should be ns1:root/a/b/ns2:root/b as Philip says because in the 
>>>>scheme I described a and b were unqualified.  As such there's no 
>>>>difference in name between b in ns1 and b in ns2 as there would be if 
>>>>they were qualified.
>>>>
>>>>I think Philip is right about the issues.  It's down to the limitations 
>>>>in XPath expressibility.  You need to say something like: b whose 
>>>>qualified parent is in namespace ns1.  Sort of 
>>>>b[qualified-parent-ns()=ns1]!
>>>
>>>b[parent::ns1:*]
>>>
>>>... or if you are matching nodes:
>>>
>>>  ns1:*/b
>>
>>My XPath knowledge is very weak, but does that allow for matching 'b' in 
>>the 'tree' of:
>>
>>ns1:root/a/b  ?
>
> No, you only asked "b whose qualified parent is in namespace ns1"
>
>>I had guessed that ns1:*//b might be better, but I think that expression 
>>would match both 'b's in the Philip's 'tree' of:
>>
>>ns1:root/a/b/ns2:root/b
>>
>>Yours confused,
>
> I'm confused what you are looking for.
>
> Given the tree:   ns1:root/a/b/ns2:root/b
>
> ns1:*/b selects nothing
> ns1:*//b selects both b's
> b[parent::ns1] selects nothing
> b[parent::ns2] selects the lowest b only
>
> What *exactly* do you want to address, and from where will you be 
> addressing it?  In a select="" using an expression (and if so from which 
> context node)?  In a match="" using a pattern (which is a subset of XPath 
> expressions)?
>
> I haven't been following the entire thread ... I just bristle when I read 
> statements like "It's down to the limitations in XPath expressibility" and 
> writing such is like waving a red cape in front of me.  I know XPath is 
> *incredibly* expressive and in the classroom I try and teach students how 
> to understand the node tree intimately in order to compose the most 
> appropriate and least wasteful XPath expressions.  The XPath exercise is 
> most often the favourite exercise of the entire week in the class.
>
> I've not been following the discussion but that statement of yours jumped 
> out at me and quickly got my attention.
>
> I hope this helps.
>
> . . . . . . . . . . Ken
>
> --
> Crane Softwrights Ltd.          http://www.CraneSoftwrights.com/x/
> G. Ken Holman                 mailto:gkholman@CraneSoftwrights.com
> Male Cancer Awareness Nov'07  http://www.CraneSoftwrights.com/x/bc
> Legal business disclaimers:  http://www.CraneSoftwrights.com/legal
>
>
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