hi,
IMHO there is no such thing of ONE data model for a SOA landscape. Moreover data models are not in the relam of SOA at all.
SOA is about services and transparency, i.e. the data model underlying one service is irrelevant to the service consumer. Data persisted by an application being exposed (in part or as a whole) as a service can be modeled in any way possible. Two services, though being orchestrated within one process, do not need to be based on the same kind of data modeling paradigm nor actual data model. This is a far reaching result of loose coupling.
What is considered to be useful is a 'global' datatype repository, e.g. the subset of customer data making it up to some customer object being exchanged via webservices with other applications has to be defined in a (service) local datatype anyway and this datatype should be defined in a global datatype repository (or service repository) to be reused on a wide scale. Global metadata if you like, or least common denominator of all the customer objects in the landscape.
One shouldn't stick to pragmatic to those global datatypes though. Sometimes, I believe, it's more useful to create variants of entities to be exchanged, to allow for something like a semantic transposition or mediation.
Summary: Data models belong to the realms of different 'sub-domains' of the landscape, data type definitions may be aggregated into global repositories.
Interesting reading (though in kind of disagreement with my view of matters) can be found <a href="http://www.tdan.com/i032ht02.htm">here</a>.
my 2 cents,
anton
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