Re: [xml-dev] Concerned about the increasing reliance on XPath

[Stephen D Green <stephengreenubl@gmail.com>]

On 9 May 2011 18:52, Philip Fearon <pgfearo@googlemail.com> wrote:
> Yes, it seems each vendor has adopted their own 'harness' for setting
> the XPath evaluation context so that saved XPaths are portable.

Yes, but this highlights my issue; they are portable *within instances of
that implementation and not (as much as we'd like) between implementations*


>
> SketchPath's approach is to create grouped sets of XPath expressions
> that are saved in simple XML files so they can be reused easily as a
> resource in other applications.
> (These same XML files are also used to set parameters and processor
> settings for an XSLT test tool).
>
> As well as the XPath itself, additional metadata is stored for each expression:
> 1. A name for the expression - other expressions can use this name to
> reuse the expression as a variable
> 2. An XPath identifying the context node for evaluation
> 3. A descriptive comment

Yes, my interest has been in Tamelizer (GoogleCode project) and this
does the same

>
> Each XML file includes a set of namespace bindings to be used for
> expression evaluation - (these are actually just XPath expressions in
> a special 'namespaces' group with names corresponding to the namespace
> prefix)

Tamelizer uses TAML-X, an XPath profile of TAML
(OASIS-open.org, potential standard in progress)
which puts namespace bindings in each TAML-X
file. I didn't realise it but it might be that more portability
would come by putting the bindings into each TAML
test assertion (as I recently suggested for Schematron
too) so that they can be copied and pasted between
files.

I do notice though that some standards are appearing
which express test assertions in a spec using XPath
and I wonder if they have thought about these details
like namespace bindings and making explicit any defaults.

>
> - A sample XML fof the grouped XPath expressions and their metadata is
> shown below
>
> <?xml version="1.0" encoding="UTF-8"?>
> <cwb:expressions xmlns:cwb="http://www.qutoric.com/2010/XPathCollection";>
> <cwb:xsl-param group="" source=""/>
> <cwb:namespace-declarations>
> <cwb:expression name="spec">
> <cwb:main>'http://expath.org/ns/xmlspec'</cwb:main>
> <cwb:comment>Created: 09/05/2011 18:18:45</cwb:comment>
> </cwb:expression>
> </cwb:namespace-declarations>
> <cwb:xpath>
> <cwb:global>
> <cwb:expression name="code-1">
> <cwb:main>p/code</cwb:main>
> <cwb:context>/spec/body/div1[3]/div2[2]</cwb:context>
> <cwb:comment>Created: 09/05/2011 18:24:16</cwb:comment>
> </cwb:expression>
> </cwb:global>
> <cwb:local>
> <cwb:group name="alpha">
> <cwb:expression name="header-1">
> <cwb:main>/spec/header</cwb:main>
> <cwb:comment>Created: 09/05/2011 18:16:13</cwb:comment>
> </cwb:expression>
> </cwb:group>
> <cwb:group name="beta">
> <cwb:expression name="head-1">
> <cwb:main>/spec/body/div1[1]/head</cwb:main>
> <cwb:comment>Created: 09/05/2011 18:17:44</cwb:comment>
> </cwb:expression>
> <cwb:expression name="head-2">
> <cwb:main>/spec/body/div1[1]/head</cwb:main>
> <cwb:comment>Created: 09/05/2011 18:18:00</cwb:comment>
> </cwb:expression>
> <cwb:expression name="Name1">
> <cwb:main>count(spec/body/div1/div2)</cwb:main>
> <cwb:comment>Created: 09/05/2011 18:19:28</cwb:comment>
> </cwb:expression>
> </cwb:group>
> </cwb:local>
> </cwb:xpath>
> <cwb:recyclebin/>
> </cwb:expressions>

Yes, I like that.

Maybe there would be more portability if your XML language could
also allow every group to inlude the bindings though, like this:

             <cwb:group name="alpha">
                <cwb:expression name="header-1">
                    <cwb:namespace-declarations>
                        <cwb:expression name="spec">
                            <cwb:main>'http://expath.org/ns/xmlspec'</cwb:main>
                            <cwb:comment>Created: 09/05/2011
18:18:45</cwb:comment>
                        </cwb:expression>
                    </cwb:namespace-declarations>
                    <cwb:main>/spec/header</cwb:main>
                    <cwb:comment>Created: 09/05/2011 18:16:13</cwb:comment>
                </cwb:expression>
            </cwb:group>


See also my own XPath based test assertions for the Universal Business
Language using the TAML-X profile

http://lists.oasis-open.org/archives/tag-comment/201104/zip00000.zip
and earlier ones here for a previous version of TAML
http://lists.oasis-open.org/archives/ubl-comment/201003/msg00001.html

Maybe here too each test assertion should optionally allow
the namespaces to be declared for it locally.

---

Stephen D Green

>
> -----------
>
> Phil Fearon
> http://qutoric.com
>
> On Mon, May 9, 2011 at 5:13 PM, G. Ken Holman
> <gkholman@cranesoftwrights.com> wrote:
>> At 2011-05-09 16:49 +0100, Stephen D Green wrote:
>>>
>>> I think we tend to hope that XPath expressions can be
>>> written such that they are immune from such implementation
>>> specifics
>>
>> XPath cannot function in a vacuum.
>>
>
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