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Model of Concurrency in DAML-S

From: Monika Solanki <monika@dmu.ac.uk>
Date: Mon, 22 Sep 2003 07:47:28 +0100
Message-ID: <3F6E9B00.5040806@dmu.ac.uk>
To: www-ws@w3.org

In DAML-S we have the notion of an Atomic service and a Composed 
Service. Composed services are built out of Atomic Services using 
Control constructs. The control constructs that we can use for 
specifying concurrency are Split, Concurrent, Parallel, Split-Join, 
Fork-Join, unordered etc. Now as per my understanding, if I specify say 
Split as a control construct, for a composite service built out of two 
atomic services, it would mean that both of them execute independently.. 
Basically as per my conclusion, atomic services  can either execute 
sequentially or in parallel, independent of each other.

For a scenario given below, I have two thoughts

1. There are 3 composite processes, A, B and C.
2. All the 3 start execution in parallel i.e split.Now after some 
computation, B needs a value from A.It requests A for the value, gets 
the value and carries on computation.
3. After some time B needs value from C. It requests C for the value, 
gets it and carries on computation, and finally terminates
4. In some cases it may happen that one of the processes may have to 
wait for some value from some other process, because it did not finish 
on time .

Option 1:
 >From here we see that some kind of a synchronization is needed between 
the 3 processes. Can we capture that in the DAMl-S model ? Is such a 
specification part of the model ? Do we have control constructs for them?
 From all the examples that we have on the website and the 
documentation, I have not been able to answer all these questions. I 
want to build up such kind of an example and analyse the level of 
complexity that can be handled through the DAML-S specs.

Option 2:
Since communication will actually happen within the atomic services of 
these composite services and since atomic services can execute 
sequentially or independently in parallel with each other, the 
 representation of this problem in DAML-S is possible in terms of atomic 
services and control constructs.

I am certain abut option 1, however option 2 may solve this problem. I 
want a second opinion about option 2. Will the actual solution need new 
constructs or is option 2 the solution


Monika Solanki
Software Technology Research Laboratory(STRL)
De Montfort University
Hawthorn building, H00.18
The Gateway
Leicester LE1 9BH, UK

phone: +44 (0)116 250 6170 intern: 6170
email: monika@dmu.ac.uk
web: http://www.cse.dmu.ac.uk/~monika
Received on Monday, 22 September 2003 02:42:17 UTC

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