I just stumbled across a mildly interesting article,
A Conversation with Steve Ross-Talbot
"Merging the Worlds of Academics and Practitioners",
ACM Queue vol. 4, no. 2 - March 2006.
In it, among other things, Ross-Talbot claims that for practical use the
Pi-Calculus
(search on
lambda-the-ultimate.org)
is clearly superior to
Petri net theory.
Apparently, the Pi-Calculus allows callbacks to change the dependency
graph on the fly, while Petri Nets must be static.
He seems to say that from that it follows (he doesn't say why) that
the multiple thingees using the Pi-Calculus are composable while
multiple Petri Nets are not. If accurate, that's
interesting, as composability is a big advantage in practical
robustness... (For comparison, mutex locks are not composable but
transactions are, which is one of the many advantages of
transactions.)
Apparently his startup released and maintains their
pi4soa
"Pi Calculus for Service Oriented Architectures" toolkit under an Open
Source (Apache) license.