Petri Nets-Data Dictionary

Petri Nets-Data Dictionary

Petri nets — Formal technique for describing concurrent interrelated activities 

Consists of four parts

(1)             A set of places

(2)             A set of transitions

(3)             An input function

(4)             An output function

Originally of interest to automata theorists Found wide applicability in computer science

Performance evaluation Operating systems

Marking of a Petri net Assignment of tokens Tokens enable transitions

Petri nets are non-deterministic

If more than one transition is able to fire, then any one can be fired

Use of inhibitor arcs an important extension: Small circle instead of arrow

A transition is enabled if

At least one token is in each of its (normal) input arcs and No tokens on any of its inhibitor input arcs