AW: [wsn-comment] [WS-Topics 1.3] TopicExpressions

["Johannes Echterhoff" <johannes.echterhoff@igsi.eu>]

Hi.

This is certainly a problem that, afaik, is only solvable when Xpath is used
as topic expression dialect. See clause "8.2 Intermediary Changes of
Namespace Prefixes" in the "WSRF Application Notes" online at
http://docs.oasis-open.org/wsrf/wsrf-application_notes-1.2-cd-02.pdf.

Kind regards,
Johannes Echterhoff



> -----Ursprüngliche Nachricht-----
> Von: Bram Van Dam [mailto:bram.vandam@foresee.be]
> Gesendet: Freitag, 12. Juni 2009 14:36
> An: wsn-comment@lists.oasis-open.org
> Betreff: [wsn-comment] [WS-Topics 1.3] TopicExpressions
> 
> Hi,
> 
> I've got a bit of a problem with the way that wsnt:TopicExpression
> deals
> with topics and topic namespaces. Supporting multiple dialects is
> obviously a good thing, and defining several standard dialects is even
> better. Unfortunately, the content of the wsnt:TopicExpression field is
> a plain old string. Sure, the content depends on the dialect, but with
> all the standard dialects the content is an xsd:token with a very ugly
> regex applied to it. This makes it very difficult to work with,
> particularly when different namespaces are applied. XML namespace
> prefixes are not set in stone, and can change as XML is read and
> rewritten. The content of string fields, however, does not change,
> regardless of whether or not they are in a QName format.
> 
> For instance, if you take the following XML excerpt, run
> marshall/unmarshall it with JaxB, it will break:
> 
> <Topic
> Dialect="http://docs.oasis-open.org/wsn/t-1/TopicExpression/Concrete";
> xmlns:tns="myTns">tns:MyTopic</Topic>
> 
> Because tns:MyTopic is a string, XML parsers treat it as such. The tns
> namespace therefore appears to be unused and might be discarded. Or
> renamed, to ns1 for instance, thus rendering the tns:MyTopic string
> unusable.
> 
> This essentially makes working with the predefined Topic dialects a lot
> harder than it should ideally be.
> 
> Should any updates to the Topics spec be planned, I think it might be
> useful if this were taken into account and that perhaps some other
> format is defined.
> 
> If I've misinterpreted this part of the spec, feel free to rub my nose
> in it  :-)
> 
> Thanks,
> 
>    - Bram
> 
> 
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