Essential Business Process Modeling

Petri Nets

The Petri network (or Petri net ), a notion devised in 1962 by the mathematician Carl Adam Petri, is a formal graphical process modeling language that can design systems as diverse as train track switches and business processes. With respect to the latter, Petri nets help describe—and indeed, can be used to implement—the semantics of process control flow, including basic branch and join rules, as well as more complicated synchronization scenarios; notably, dead path elimination , a core topic in the languages WSFL and BPEL. Petri net theory saturates the literature on process patterns, a topic introduced in Chapter 4. The keen analysis of this work, undertaken by a group of pro-Petri authors referred to in this book as the P4, injects much-needed rigor into an historically ambiguous and haphazard subject. Though among BPM champions it lacks the renown of the pi-calculus, the Petri net is a valuable abstraction and merits the attention it has been paid.

Petri Nets in a Nutshell

The Petri net’s characteristic appearance is that of an unusual assembly of circles, rectangles, arrows, and black dots. The beginner might at first mistake it for a state-transition diagram, reasoning that the circles and rectangles are states, the arrows transitions, and the dots some other curious artifact specific to the model. But although the Petri net shares with the state machine a preoccupation with the notion of state, to compare the two is like comparing apples and oranges.

In Petri’s ...