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Thanks for the replys so far. Let me make this more
specific - the immediate goal is not query optimisation or federated search (the
same query across multiple sources), but query answering that relies on joins
between two or more independent databases or sources. Further, I am
specifically not looking at global-as-view systems, in which the system knows in
advance how to map queries expressed in its mediated relations to queries
expressed in web service interfaces to the source databases. From my
limited understanding, tools like Siri, Ontology Works and Ontoprise are
global-as-view systems.
Rather, we are looking at Local-as-view systems, in
which there are known mappings from the relations exposed by the sources to
fragments of the relations in the mediated schema. This means we can pick our
sources at run time based on factors such as cost, trustworthiness or even
whether the system is up. Systems from the period 1995 to 2005 include
Information Manifold, Info Master and SIMS. I'm trying to find out whether
systems like that have been exploited in commercial tools, and if not, why
not?
Doing this declaratively would seem to require both an
ontology description of the contents of a data source and a description of
the source itself - the queries it exposes, the costs of queries, etc. One
question that springs to mind is whether this could be mediated through a UDDI
equivalent system?
Sean Barker, Bristol
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I've just been looking at some of the work on
automatic query decompostion. It looks like there was a great deal of work in
the late nineties, see for example Alon Halevy "Answering Queries Using Views: A
Survey" but more recent work looks thinner on the ground, although there is some
on using T-boxes. Given the age of the work, are there any tools or systems out
there that support automatic query decomposition? or if not, why
not?
Sean Barker,
Bristol
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