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[moca] Re: RE: RE : synchronous implementation of Pi calculus with choice?



Hi, 

> The thing that struck me is the problem of implementing a language
which
> may have multiple channels involved in multiple distributed choice
> operations.

Besides the problem of failures that is already being discussed by 
others people in this forum, there is another consensus problem 
that arises when trying to implement in a distributed system a language

like the full pi-calculus (as described in the first paper on the 
pi-calculus by Milner et al.) or more in general a language with mixed 
choice, i.e. choice involving both input and output channels(*). This
is 
related to impossibility results like the leader election on certain
symmetric networks or the (symmetric) dining philosophers. 

If you are interested, you can find a description of the problem on

 C. Palamidessi. Comparing the Expressive Power of the Synchronous and 
 the  Asynchronous pi-calculus. Mathematical Structures in Computer 
 Science. To appear. 
 (http://www.cse.psu.edu/~catuscia/papers/pi_calc/mscs.ps) 

Mihaela Herescu and myself have proposed a probabilistic solution to
the
problem: we have gives an embedding of the full pi-calculus in a 
probabilistic version of the asynchronous pi-calculus, and we have 
proposed a distributed implementation of the latter (the code is
written 
in Java, but the implementation is distributed in the sense that it
uses
message-passing, not shared memory). You can find the details in 

 M. Herescu and M. Herescu. Probabilistic asynchronous $\pi$-calculus.
 Proceedings of FOSSACS 2000, volume 1784 of Lecture Notes in Computer 
 Science, pages 146--160. Springer-Verlag, 2000. 
 (http://www.cse.psu.edu/~catuscia/papers/Prob_asy_pi/report.ps) 

 C. Palamidessi and M. Herescu.A Randomized Distributed Encoding of the
 Pi-Calculus with Mixed Choice. IFIP TCS 2002: 537-549
 (http://www.cse.psu.edu/~catuscia/papers/prob_enc/report.ps) 

 Mihaela Herescu, Phd Thesis. http://www.cse.psu.edu/~herescu/thesis.ps

(*) Note: I think that the full pi-calculus with mixed choice is
more suitable than its less expressive versions (pi-calculus with 
input-guarded choice only, asynchronous pi-calculus), to describe 
transactions. I am very much interested in this topic too.
Unfortunately
I am traveling and I am not able to check my email regularly. I will be

back next Monday and I hope it won't be too late to be involved in this

very interesting discussion. 

Greetings to all the people of the moca list, -Catuscia



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