Re: [ubl-dev] Re: XPath expressions in UBL / Signatures

["Roberto Cisternino" <roberto@javest.com>]

Hi,
I believe in XPath "no prefix" do not means "default namespace" so
namespace prefix must be always used for querying namespace aware
documents.

I agree with you that XPath is not self describing its context of use, so
I would see a few indications included into UBL 2.1 to provide a
consistent way of using XPath into UBL documents (at least for selecting
internal information).

XPath 2.0 could be enough for building expressions that are used to select
internal information om a given document.

For instance it could just simply mention that XPath expressions used on
UBL document instances must use UBL known prefixes (cac, cbc, ...) and the
root element could use a def: prefix to indicate a default prefix.

XPath 3.0 is welcome, but the business can't wait its implementation, so
it could be nice to have XPath 2.0 used with UBL in a meaninful way.

What do you think ?

Roberto

> Sorry, my last link was to the wrong xml-dev posting, it should be
> http://lists.xml.org/archives/xml-dev/201105/msg00066.html
> ----
> Stephen D Green
>
>
>
> On 12 May 2011 08:28, Stephen D Green <stephengreenubl@gmail.com> wrote:
>> It would be premature to make a comment on this to the ubl-comment list
>> so I thought I'd bounce it off ubl-dev and see if anyone can give it a
>> sanity
>> check:
>>
>> We just had some debate on xml-dev about the goods and the bads about
>> the growing use of XPath expressions.
>>
>> http://lists.xml.org/archives/xml-dev/201105/threads.html#00007
>>
>> One of the upshots of this was that I put forward a view and supported
>> it
>> and it didn't get completely shot down that XPath expressioons aren't
>> yet
>> fully portable across different applications/implementations. The
>> problem
>> is mainly with XPath expressions used without any formally defined
>> binding
>> of the namespaces, i.e. if standalone and with an underspecified binding
>> of a) default namespaces and b) any prefixes/namespaces. The XPath
>> spec does not define how applications must cater for this as it expects
>> this
>> to be specified in other standards which make use of XPath (such as
>> XSLT).
>>
>> Does this have ramifications for UBL and its use of XPath, particularly
>> in
>> the XML signatures / signature extensions to UBL? Is it clear enough
>> what
>> an application has to do about any default namespace in such an
>> expression
>> and about prefix and namespace bindings? If not, I wonder if a comment
>> is in order. Without anything specific enough about how to
>> execute/evaluate
>> an XPath expression, different applications may (validly) return
>> different
>> results for the same expression and the same target/context, it seems.
>> (I
>> note too that UBL uses XPath expressions in elements besides signatures
>> but these have been around since before 2.1.)
>>
>> At the same time, it seems another upshot of the xml-dev discussion was
>> the news that XPath 3.0 may go some way to solving portability issues by
>> allowing fully qualified element names
>> http://lists.xml.org/archives/xml-dev/201105/msg00065.html
>> so maybe future UBL specs could recommend these once they become
>> standard and adequately supported; but that day might be some way off.
>> ----
>> Stephen D Green
>>
>
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-- 
* JAVEST by Roberto Cisternino
*
* Document Engineering Services Ltd. - Alliance Member
* UBL Italian Localization SubCommittee (ITLSC), co-Chair
* UBL Online Community editorial board member (ubl.xml.org)
* Italian UBL Advisor

  Roberto Cisternino

  mobile: +39 328 2148123
  skype:  roberto.cisternino.ubl-itlsc

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