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Re: [xml-dev] RE: Caution using XML Schema backward- or forward-compatibility as a versioning strategy for data exchange

> Not using a codelist but using a method attribute seems to solve
> the problem with no need for new url. That seems to be the key.
> Add metadata everywhere in version 1. I still wonder: Is RDF/S
> going to be a valid way to do this? Would it work? It does seem
> to be becoming the standard way to add metadata for semantics.

With example
what meaning does this have? If it isn't clear what distance is meant
then maybe there is a need for *two* new web services:
- each specifying within the WSDL the meaning of the distance
- one for the first meaning and another for the second
- both being a distinct improvement on the first
- the original being preserved for consumer compatibility where
   an attribute like 'method' might break the WSDL consumers
This just isn't likely to happen though because there might be
all sorts of similarly vague elements throughout the WSDL, each
perhaps needing new versions at some point - and a new url
or several new urls for each case just doesn't seem acceptable.

Maybe if the attribute was not added in the first place then there
is a way to add the metadata it would have contained in another
way which doesn't break the WSDL consumers. The missing
piece seems to me to be 'tool support'.

Maybe if OWL were used to add the metadata (as an afterthought
if an attribute like 'method' was missed from version 1) there might
be a way for a change in such metadata to trigger a signal in the
web service consumer. Perhaps that needs to be added to tools
and maybe standardization is needed too. I would love to be on the
committee deciding what to call any possible extension of WSDL
or combination of WSDL and OWL say - maybe there is a way
to call it WSDL-OWL and switch letters to make it WS-LD-OWL,
pronounced 'wise-old-owl' :-)

I don't know enough about WSDL but when working with ebXML
I asked for an attribute 'externalDocumentDefRef' to be added to
ebXML BPSS. This, were there the tool support, could perhaps
allow a pointer to semantic metadata to be linked to a web service
via CPP/A and ebBP definitions. I would think tools would have to
detect any changes in the metadata and signal that something has
to be looked into as a thrown exception (fatal or otherwise). So
with the right ingredients in the web service, it is possible for
semantic changes to be automatically picked up by suitable tools.

Stephen Green

SystML, http://www.systml.co.uk
Tel: +44 (0) 117 9541606

http://www.biblegateway.com/passage/?search=matthew+22:37 .. and voice

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