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Subject: Re: [ubl-dev] Re: XPath expressions in UBL / Signatures
Plus the fact that messages might be read some time in the future by software unknown at the time the messages were produced and using unknown versions of XPath suggests again the need to make the XPath version explicit and to allow for local declarations along with the XPath of the prefix and namespace bindings, especially important for use when pre-XPath 3.0 versions are used. In the example in the recent in-progress package the namespace and prefix are declared in the XPath element itself and retrieved from the namespace axis, I gather, so it is a matter of making it clear that this is how it is done explicitll in the spec and maybe considering what else might have to be clear too. ---- Stephen D Green On 12 May 2011 22:16, Stephen D Green <stephengreenubl@gmail.com> wrote: > The version of XPath can determine different results so I would > hope that the elements in UBL and signature extensions would > cater for this by providing some means to declare which version > of XPath is used (by reference to the main URL for the respective > version seems a good idea, or perhaps with some appropriate > datatype which can make it unambiguous which version is used). > I would consider also having perhaps a special datatype which > allows the namespaces and respective prefixes to be declared, > assuming too that it will not always be just the UBL ones which > might be used - might there be customs ones too perhaps. This > relates to what is provided in the business document. In there > spec I would want to see at least a mention that different apps > interpret XPaths different ways, such as having different ways of > handling any default namespace and prefix (and absence of a > prefix for the defaut namespace) and that this allowed difference > can be applied differently to different versions of XPath. So a > warning seems to be in order to underline the need for this to be > tested both sides of any message transmission/exchange process > especially when each party uses different software to handle the > XPath expression evaluations and that restesting might be in order > if the software changes. > > ---- > Stephen D Green > > > > On 12 May 2011 19:24, Roberto Cisternino <roberto@javest.com> wrote: >> 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 >>>> >>> >>> --------------------------------------------------------------------- >>> To unsubscribe, e-mail: ubl-dev-unsubscribe@lists.oasis-open.org >>> For additional commands, e-mail: ubl-dev-help@lists.oasis-open.org >>> >>> >> >> >> -- >> * 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 >> >> [UBL Technical Committee] >> http://www.oasis-open.org/committees/ubl >> >> [UBL Online Community] >> http://ubl.xml.org >> >> [UBL International Conferences] >> http://www.ublconference.org >> >> [UBL Italian Localization Subcommittee] >> http://www.oasis-open.org/committees/ubl-itlsc >> >> [Iniziativa divulgativa UBL Italia] >> http://www.ubl-italia.org >> >> >> >
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