William:
Good email, good walk through of the
options.
I would be very uncomfortable with option
#3, it seems to be gratuitious reinvention.
I would be very much in favour of option
#1, this seems to be the most natural. Adding additional non-normative
text to describe certain precautions to be considered.
sgg
++++++++
Steve Graham
(919)254-0615 (T/L 444)
STSM, On Demand Architecture
Member, IBM Academy of Technology
<Soli Deo Gloria/>
++++++++
"Vambenepe, William N" <>
wrote on 08/09/2004 10:19:26 PM:
>
> Hi all,
>
> On the call today I took an AI to start a thread to further discuss
> issue 24.
>
> The problem is to decide unambiguously what namespace declarations
to
> take into account when evaluating an Xpath expression contained in
a
> QueryResourceProperty element. On the call, we pretty much agreed
that
> we want some kind of namespace mapping to take place for prefixes
in the
> Xpath expression (the alternative, string comparison of prefixes between
> the Xpath expression and the target XML document, is not desirable).
The
> question then is what namespace declarations to take into account.
>
> Option #1: whatever is in scope at the QueryResourceProperty element:
> the namespace declaration can be on any parent of the
> QueryResourceProperty element, as long as they haven't been overwritten
> they are in scope.
>
> Option #2: only the namespace declarations that are on the
> QueryResourceProperty element. Namespace declarations on parent elements
> are irrelevant for the Xpath processing.
>
> The benefit of #2 is that you isolate yourself from namespace
> declarations added later on by other software modules (for example
added
> on the SOAP envelop). But the problem of #2 is that these same software
> modules might decide to move namespace declarations around (for exmaple
> move them all to the root element).
>
> In any case, there always is a risk that some module will mess up
with
> namespace declarations (and rename all the prefixes for example) and
> this module will likely not touch the Xpath expression itself. The
only
> way for us to be 100% safe is to not use XML namespace mechanisms
for
> namespace declarations that apply to the Xpath expression but specify
> them in our own format. This would be option #3:
>
> Option #3: Create a NamespaceDeclaration element and allow people
to
> stuff an arbitrary number of these in the QueryResourceProperty element.
> The NamespaceDeclaration element would look something like that:
> <NamespaceDeclaration>
> <Prefix>foo</Prefix>
> <Namespace>http://foo.com/foo</Namespace>
> </NamespaceDeclaration>
> Implementers would use these mappings to know what to map prefixes
in
> the Xpath statement to.
>
> At this point, I think we should either do the "right thing"
(at the
> cost of more coding work for the WSRF implementers) which is #3 or
the
> intuitive thing which is #1. I say forget #2 (I only listed it here
> because we talked about it on the call).
>
> Between #1 and #3 I would pick #1 for simplicity, along with some
> warnings in the text. If we get real-life experience that this is
a
> problem (during interop) then we can switch to #3 at that point.
>
> Thoughts?
>
> Regards,
>
> William
