Re: XPath expressions in UBL / Signatures

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

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
>