

A Simple Visual Model for Promises - remotesynth
http://flippinawesome.org/2013/10/14/a-simple-visual-model-for-promises/

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drewhk
There is a particularly interesting subset of Petri Nets -- (Extended) Free
Choice Petri Nets that I actually fell in love with. If someone is interested
in learning about them one of the best books on the subject is available here:
[http://www7.in.tum.de/~esparza/bookfc.html](http://www7.in.tum.de/~esparza/bookfc.html)

There are some limitations of the model, but the theory is still fascinating
(especially the duality property of Well-Formed PNs).

