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SOAP services as database query interfaces / SOAP design patterns?

From: Dan Brickley <danbri@w3.org>
Date: Mon, 18 Nov 2002 16:55:17 -0500 (EST)
To: <www-ws@w3.org>
Message-ID: <Pine.LNX.4.30.0211181629280.1318-100000@tux.w3.org>


I was looking again at the registry of (public) SOAP Web Services at
http://www.xmethods.com/ and was struck (again) by the fact that many,
perhaps most, of these services appear to be based around database
queries, ie. they return a single item or list of items corresponding to
record(s) picked out by the argument(s) passed in the SOAP request.

Lottery results given a region and date. Car rental quotes given a query
specification. Zipcode to lat/long mappings. Searches against Shakespeare
etexts. Telephone codes from city names. Weather forecasts from zipcodes.
Book data given ISBN. Whois lookups. Population size given countrycode.

etc etc. You get the idea. SELECT/FROM/WHERE-esque use cases.

So I'm interested in whether this recurring pattern of Web Service
deployment can be captured for machine use, or less ambitiously, whether
anyone has offered a more careful analysis than mine of the ways in which
real live SOAP services are being deployed in the public Web as a way of
exposing database lookup facilities. I'd like to be able to consult a
database of SOAP services and pick out those which offer such lookup-based
information services. I'd like to know which of those have an interaction
pattern that typically returns a list of 'hits' versus which return a
single 'hit'. I'd like to know how each service represents a search with
zero hits versus a search that fails for some other reason (malformed
query; database temporarily down etc.).

Basically it strikes me that there is a lot of hidden commonality across
these lookup-based Web services, and that there would be significant
benefit to having machine-friendly characterisations of aspects of that
commonality. Many of them are probably thin wrappers for SQL queries and
ODBC/JDBC/DBI anyway. My current understanding of WSDL and the Web Service
Description effort is that it would support richer
description/classification of these services, but doesn't come with innate
support for representing these.

Um, I guess I'm rambling now. The purpose of this mail was to enquire
whether folk on www-ws could point me to any work on classifying
query/lookup based SOAP services, eg. using WSDL extensions, RDF/DAML-S etc.

Thanks for any pointers,


ps. this is related to my earlier enquiry about the use of W3C's XQuery
for Web Service discovery, see thread beginning

Received on Monday, 18 November 2002 16:55:17 UTC

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