Communicating Mobile Processes

Advanced Programming Specialist Group event

Thursday 13th January 2005, 6.00 pm

BCS, Davidson Building, 5 Southampton Street, London WC2. (Southampton Street runs north from The Strand to the Covent Garden Piazza; nearest rail stations - Charing Cross, and Covent Garden).

Professor Peter Welch, University of Kent.

This talk presents a new model for mobile processes in occam-pi (which gives a secure and efficient binding of key elements from Hoare's CSP and Milner's pi-calculus into a programming language of industrial strength). A brief overview of channel and data mobility in occam-pi will also be presented. The audience need not have prior knowledge of either classical occam, occam-pi, CSP or the pi-calculus!

A process, embedded anywhere in a dynamically evolving network, may suspend itself mid-execution, be safely disconnected from its local environment, moved (by communication along a channel), reconnected to a new environment and reactivated. Upon reactivation, the process resumes execution from the same state (i.e. data values and code positions) it held when it suspended.

Its view of its environment is unchanged, since that is abstracted by its synchronisation (e.g. channels and barriers) interface and that remains constant. The environment behind that interface will (usually) be completely different. The mobile process itself may contain any number of levels of dynamically evolving sub-network.

This model is simpler and, in some ways, more powerful than our earlier proposal, which required a process to terminate before it could be moved. Its formal semantics and implementation, however, throw up extra challenges.

We present details and performance of an initial implementation. An example application of this technology supports one of the 'Grand Challenge for Computer Science' areas: the large scale modelling of biological mechanisms (involving millions of dynamically assembling and communicating processes), to which the notions of Communicating Mobile Processes are a natural fit.

Note that the overheads for semantic comprehension and analysis, as well as for run-time, of occam-pi are sufficiently low so that systems involving millions of processes are practical on modest processor resources (e.g. a laptop).

Free, but please ask Dr Frank Martin to add your name to the security list by e-mailing him at -: Notification is required individually for each meeting.

CPD Value:
Half unit

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