Friday, June 24, 2011

Ugo Montanari's talk 22 June 2011

on the occasion of a celebration in Milan in honour of Gianni Degli Antoni.

Ugo spoke about his latest work about a compositional calculus for Petri nets using the wire calculus of Sobocinski.

I was disappointed that he didn't mention our work on connectors, which we have spoken about for years, including in joint projects, and which goes back to 1997 or even 1987.

In particular because the work of Sobocinski derives from ours. It arose in discussions with me (he even agreed that it was a joint project at the time), and lectures given by me, one at CT 2008 in Calais, where I emphasized the important difference between the parallel communication in Span(Graph) and that in conventional process algebras such as CSP and CCS. The slides are available at the CT site.
Sobocinski actually carried out a student project with me in 1997 at the University of Sydney on Span(Graph) and was present at our talks at AMAST 1997 in Sydney, one of which was on representing Petri nets in Span(Graph). He refers to both our AMAST papers in his article in CONCUR 2010, including the following quote:
"The operations of the calculus presented in this paper are fundamentally different to those utilised in the aforementioned literature. Indeed, they are closer in nature to those of tile logic [13] and Span(Graph) [18] than to the operations of CCS. More recently, similar operations have been used by Reo [2], glue for component-based systems [8] and the wire calculus [30]. Indeed, in [17] Span(Graph) is used to capture the state space of P/T nets; this work is close in spirit to the translation from nets to terms given in this paper."

I might say that even Arbab was influenced by us. He visited us in Como in 2000 and was talking about Manifold. I told him his connectors were not compositional. I believe his subsequent work on Reo was influenced by our discussions. Our paper in COORDINATION 2000, prior to Reo, used compositional connectors in modelling IWIM in CospanSpan(Graph).

The point of this post is not casual.
The main contention in all our work is that concurrency theory has taken a wrong direction for thirty years, because of the choice of the wrong basic operations. We have said this in many forums including IFIP WG1.3 without apparently any reaction. For some more detailed comments see this post.

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