granularity/definition of a "service"

Hi All,

Keeping aside the "web" part, I am interested in understanding the 
semantics of the word "service". Within the web service world, what is 
the lowest level of granularity a service can have. What would be the 
most appropriate definition for the basic building block from which 
bigger units can be composed.  Services communicate via sending and 
receiving messages. Can communication primitives also be classified as 
services i.e in this context is it appropriate to consider the operation 
of sending and receiving as services themselves and can they be modelled 
as such ? The BPEL4WS specifies these and other control constructs as 
"Activity". So in this context is a "service" at a higher level of 
abstraction  then an "Activity" or do they have equivalent semantics.

-Monika
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Monika Solanki
Software Technology Research Laboratory(STRL)
De Montfort University
Gateway building, G4.61
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
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