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Unless one is say, creating ad hoc SQL queries and sending them
to a non-collocated database, why would deep schema information
be necessary? I don't think many private holders of data will
be too eager to expose all of the local schema information but
they would be willing to negotiate services that equal reports.
It is completely possible to expose the schema or to expose
an interface schema that middleware then transforms into
the local schema. As you say, Thomas, mappings. BTW, why would I
need OWL to implement what is essentially a business object?
I don't see the problem. What am I missing?
Joe, you may be asking for ad hoc querying. If so, it is
doable but not often done for external resources. Crystal
Reports and ODBC make it possible. The trick, as you note,
is that given a flat set of descriptions without the integrity
information, the security objects, etc., it is hard to build
a good query and easy to screw up a database if the ODBC
connection is badly configured. For that reason, the service
should provide the right codes and relationships for its
set of queries available by the role of the authorized and
authenticated querying agency. NCIC for example, has a
set of standard queries.
len
From: Thomas B. Passin [mailto:tpassin@comcast.net]
Chiusano Joseph wrote:
> I sent this e-mail over 24 hours ago to the W3C Semantic Web Services
> Interest Group, and I did not receive any pushback (a gentle way of
> saying I did not receive a reply ;). So I'm wondering if that is good or
> bad....
> Here is a scenario:
> ...
>
> At this point, we need the following to happen:
>
> (1) The Hotel Reservation Web Service must relay to the Travel Agent Web
> Service the information that is missing, and
> (2) The Travel Agent Web Service needs to obtain that missing
> information from the Travel Agent relational database
>
> It is #2 above that I perceive as a current gap - i.e. unless the Travel
> Agent relational database is sufficiently "semantically aware" (i.e.
> perhaps it implements an OWL ontology whose classes and properties are
> mapped to the database tables/fields respectively), there is no
> efficient and accurate way that the required information can be obtained
> from the Travel Agent relational database.
> </Scenario>
>
This seems to be no different from any other data integration problem.
In general, it is impossible to automatically map from one database
schema to another, because most databases do not/cannot contain enough
explicit schema and ontology information to do so. In many if not most
cases, people will have to create the mapping, or at least to adjust an
automatically-obtained mapping. If not a map, then a wrapper to make
the database respond like, say, and rdf database.
This is one reason I have never believed in the practicality of fully
automated service composition (or fully automated web service discovery,
for that matter, and for similar reasons). But if you say that the
agents are only to operate within known domains, the mappings or
wrappers could be prepared in advance, just as is done today.
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