Flow diagrams to Petri nets

This document describes how the FD2PN component has been reused for several workflow languages. This component features a reusable transformation from a Workflow concept to a Petri net, which is able to deal with several of the patterns defined in the Workflow patterns catalog.

The menu provides links to the different artefacts of the case study.

Code for Bentō:

Event-Driven Process Chains (EPC)

Event-driven Process Chains (EPCs) is a type of flowchart used in business process modelling. EPC models describe the flow of control of business processes as a chain of functions, events, and logical connectors. Functions represent activities in a business process. An event expresses a precondition (trigger) for a function or a postcondition that signals the termination of a function. Logical connectors and, or, and xor are used according to their names to build the control flow of a process in a natural way [HOS05].


The following diagram corresponds to the EPC meta-model.


The binding maps Functions and Events into Tasks in the concept. In the latter case only when the event has at least one outgoing connection. Otherwise, the event is considered a FinalTask. This kind of distinction also happens with the logical connectors. In this way, an And connector might be mapped into a ParallelSplit (when it has several outgoing connections) and/or a Synchronization (when it has several incoming connections). Similarly, a Xor connection is mapped to an ExclusiveChoice (when it has exactly one incoming connection and several outgoing ones) or to a SimpleMerge (when it has more than one incoming connection and exactly one outgoing one). Finally, Or connections are mapped to a MultiChoice when they have one incoming and severl outgoing connections. ControlFlow objects are naturally mapped to FlowEdges. As ControlFlows may actually connect Functions, Events or LogicalOperators through different source (fsource, esource, lsource) and target references (ftarget, etarget, ltarget), an OCL expression needs to check what they connect by looking at the non-empty references.

binding epc {  
	concept   FD   : "platform:/resource/bento.examples.flow_diagrams.petrinets/metamodels/flow_concept.ecore"
	metamodel EPC  : "platform:/resource/bento.examples.flow_diagrams.petrinets/bindings/epc2pn/epc.ecore"
	class FlowDiagram     to EPCDiagram
	class Node            to ProcessObject 
	class Task            to Function, Event when if self.oclIsKindOf(EPC!Event) then self.outgoing->size() > 0 else true endif
	class FinalTask       to Event when self.outgoing->size() = 0 
	class ParallelSplit   to And when self.outgoing->size() > 1
	class Synchronization to And when self.incoming->size() > 1
	class ExclusiveChoice to Xor when self.incoming->size() = 1 and self.outgoing->size() > 1
	class SimpleMerge     to Xor when self.incoming->size() > 1 and self.outgoing->size() = 1
	class MultiChoice     to Or  when self.incoming->size() = 1 and self.outgoing->size() > 1
	class FlowEdge        to ControlFlow
	feature FlowDiagram.nodes is objects
	feature FlowDiagram.edges = self.flows->select(f | f.oclIsKindOf(EPC!ControlFlow)) 
	feature Node.outs is outgoing -- defined by all children classes of ProcessObject
	feature Node.ins is incoming  -- defined by all children classes of  ProcessObject
	feature Task[Event].name is name
	feature Task[Event].isInitial = self.incoming->size() = 0
	feature Task[Function].name is name
	feature Task[Function].isInitial = false
	feature FinalTask.isTerminating = true 
	feature FlowEdge."in" = if not self.fsource.oclIsUndefined() 
	                        then self.fsource 
	                          if self.lsource.oclIsUndefined()
	                          then self.esource
	                          else self.lsource
	feature FlowEdge.out = if not self.ftarget.oclIsUndefined() 
	                        then self.ftarget
	                          if self.ltarget.oclIsUndefined()
	                          then self.etarget
	                          else self.ltarget