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   Re: [xml-dev] Non-schema approach to web service design: comments?

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One doesn't need to know much about web services to ask: If your 
application ain't broken (== serves its purpose well), what do you worry 
about? ;-)

VG


On Thu, 27 Oct 2005 ian.graham@utoronto.ca wrote:

> [Also: Anyone know of a good web service mailing list?? I certainly
> can't find one .... ]
>
> I want to describe our approach to Web service development, and
> get some feedback:has anyone else tried this?  Does this make
> sense?  If not, why. etc. ?
>
> Background: we are using continuous integration, so need
> easy refactoring of all code, including service interfaces.
> We use websphere as our service provider, and have (for now)
> .NET and websphere service consumers. This is an internal
> project, so we 'own' all interfaces (at least for now).
>
> We do not use WSDL/XSD to 'define' services. Instead the
> dev team uses xdoclet/JCF to decorate java classes with
> annotations defining the contract.  We have created xdoclet
> extensions to support custom constraints (e.g. checksums).
>
> The build generates the service provider code, along with WSDL
> and XSD files: the XSD's including <annotation>s in a custom,
> machine-readable format detailing the contract rules not
> expressed in the Schema. Indeed, today very little of the
> contract  is in the XSD: the goal is to place as much as
> possible in  XML Schema, the rest in the custom format.
>
> We have a simple .NET tool (partly home-built) that takes
> the WSDL/XSDs, plus the embedded annotations, and creates
> appropriate service consumer code (and constraints).  We can
> do similar things for Java consumers.
>
> What was the rationale?
>
> - Speed.  This approach is 2-4 times faster than one starting
>  with WSDL/XSD (done on a previous project). This is particularly
>  true when modifying/refactoring a service.
> - Simplicity. the annotations express business-relevant
>  constraints more easily (to developers) and completely than
>  XSD. In particular, they can specify constraints like
>  checksums and co-constraints, that are fundamental to the
>  contracts but that are not expressible in XSD.
> - Simplicity 2. We get a single (in java) book of record
>  for the contract -- whereas when we use WSDL/XSD we end
>  up with part of the contract in XML, and part in text
>  documentation (checksums, etc.).
>
> Some concerns raised have been:
>
> - Java-centred service design is a bad idea, as the overall
>  service architecture will be biased to the Java data and
>  component model (so should start with WSDL/XSD)
> - Approach could leave you high and dry if  xdoclet/JCF goes away.
> - Just Plain Bad to use a Custom non-standard approach.
>
> Thoughts?
>
> Ian
> --
> ian DOT graham AT utoronto DOT ca
>
>
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