W3C home > Mailing lists > Public > public-sws-ig@w3.org > March 2006

RE: Semantics of WSDL vs. semantics of service

From: Shi, Xuan <xshi@GEO.WVU.edu>
Date: Thu, 16 Mar 2006 14:22:02 -0500
Message-ID: <D81F456794C18B4DA3E2ABC47DBBEEF2094FC2@www.geo.wvu.edu>
To: "'Kunal Verma '" <verma@cs.uga.edu>, "'public-sws-ig@w3.org '" <public-sws-ig@w3.org>
Cc: "Shi, Xuan" <xshi@GEO.WVU.edu>

Kunal,

Thanks very much for your concerns. That's a typical question in Web
services composition. Given the example of ESRI's address geocoding Web
services, since it is a paid service, the requester needs to invoke two Web
services in order to get the result. First, the request need to invoke an
authentication service by passing the user name and password to the service
provider to generate a dynamic token, which then is used as an input
variable to invoke the geocoding service.

Here is the problem as you see the requesters have to invoke two Web
services to get the result. In my opinion, the source of the problem is that
the developers or service providers only care about how to develop the
service, but less consider how requester can consume the service in a much
simpler and easier way.

So, can we send one request to the service provider to invoke two or more
Web services? Yes, definitely. The precondition is that service providers
have to change their development routines to handle all such processes on
the server side, other than let the requester to send the request two or
multiple times to get the result.

The solution was detailed in two articles that can be accessed at:

http://www-128.ibm.com/developerworks/webservices/library/ws-intdist/
http://www-128.ibm.com/developerworks/library/ws-semantic/

You can see how to transform all kind of composite Web services into atomic
ones so that requester can just send one service request document to the
service provider who, then, has to handle all processes on the server side
to invoke multiple functions to generate a response.

That's why service deployment is so easy to the requesters by OSRR. Service
providers have to sacrifice somehow in such a process unfortunately :)

Best wishes,

Xuan



--

Do you think that all Web services can be generalized to this
approach. In many cases, it may not be possible to just send a single
request to a service, since an interaction might be needed by invoking
more than operation of the service.

An simple example could be a WS that has two operations - getQuote and
placeOrder. The user may not want to place an order until he gets the
quote. In that case, the user would have to invoke both operations of
an services as it would not be possible to just send one request to
invoke both the operations.

My question is how would OSRR handle this case? Would you not have to
model both the operations ?
Received on Thursday, 16 March 2006 19:22:39 UTC

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