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Re: atomic services with no effects or outputs

From: Monika Solanki <monika@dmu.ac.uk>
Date: Fri, 21 Mar 2003 22:03:49 +0000
Message-ID: <3E7B8C45.7000208@dmu.ac.uk>
To: Mithun Sheshagiri <mits1@cs.umbc.edu>, www-ws@w3.org
Just an info: there is a note in the comment tag of the file that states:

NOTE: This is a sketch; not a complete example

The example therefore can be made more sell sufficient.

For effective service composition, I agree with you, that ideally the 
IOPEs of every collaborating service would have to be exposed. I am not 
sure at this moment, if and how these should be made mandatory, in some 
way in the service description. Probably a parser encapsulating certain 
rules could be used. However there is little that can be achieved 
without the IOPEs.



Mithun Sheshagiri wrote:

> Hi all,
>        There are several atomic services described in the CongoProcess 
> file that neither have outputs nor effects. I was wondering how can 
> these services be of use to us (entities other than the author). In my 
> understanding services either provide you with some information (e.g.. 
> ISBN lookup service with the ISBN number as the output) or do some 
> world altering activity (e.g. the ExpressCongoBuy service whose 
> execution results in the book being shipped to its destination). The 
> former has an output and the latter has some effect. Here the output 
> or effect implies some sort of a change.
> If a service does not indicate a change of state (i.e., if it does not 
> have i/e) then how can someone who discovers the service use it (say 
> for composition). Something does change when the service is executed 
> but the service does not reveal it. I would like to draw an analogy 
> between such services with methods that have return type "void". Take 
> the example of a program that implements a counter. The increment 
> method in this program returns void after incrementing the counter. I 
> further name the method foo. If I advertise this method as a web 
> service how will one use it since he/she has no idea about its 
> internal workings. But if I return a message (add an effect/output) 
> that says "Counter_Incremented" then won't it be much easier to 
> comprehend what the service does (assuming there is a Genie that maps 
> Counter_Incremented to an my concept of counter increment)..
> What I make out of this is that as long as I don't provide an output 
> or effect, only I, as the writer of the program can use it. By 
> describing the effect, I describe the service to the extent that 
> someone else might be able to use it.
> Do I make any sense or have I completely lost it.
> mithun

Monika Solanki
De Montfort University
Software Technology Research Laboratory
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The Gateway.
Leicester LE1 9BH, UK

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email: monika@dmu.ac.uk <mailto:monika@dmu.ac.uk>
web: http://www.cse.dmu.ac.uk/~monika/ 
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Received on Friday, 21 March 2003 16:59:31 UTC

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