Process Orchestrations

Abstract

The process orchestrations chapter is the centre of gravity of the book. After introducing control flow patterns independently from specific notations, the most important process modeling notations are introduced, starting with Petri nets. Event-driven process chains are presented as a means to informally characterize simple business processes. Workflow nets are introduced as a specific variant of Petri nets that enable formal analysis of business processes. Yet Another Workflow Language is discussed and its execution semantics is described. Finally, the industry standard Business Process Model and Notation is discussed. All important concepts of the BPMN in Version 2 are described and illustrated by examples.

Bibliographical Notes

Control flow patterns are the building blocks of process orchestrations; they were introduced by van der Aalst et al. (2003c). A revised version was published in Russell et al. (2006). Petri nets were introduced by Petri (1962). Girault and Valk (2010) published a textbook on Petri nets that investigated in detail the specification and verification of computer systems.

There are numerous extensions of Petri nets, including the colour extension reported in Jensen and Kristensen (2009), which looks at modelling and validation of concurrent systems. van der Aalst and Stahl (2011) provide a comprehensive approach to modelling processes, based on coloured and hierarchical Petri nets.

Workflow nets are introduced in van der Aalst (1998) and also in van der Aalst and van Hee (2004), where organizational aspects and tools are also addressed. Event-driven process chains are introduced in Scheer (2000). The application of event-driven process chains is reported in Scheer et al. (2004). An investigation of the formal semantics of event-driven process chains is given in Kindler (2004); run time considerations are reported in Cuntz and Kindler (2005). Investigations regarding the semantics of the or join are reported in Mendling and van der Aalst (2007) and in Gfeller et al. (2011).

Yet Another Workflow Language is introduced in van der Aalst and ter Hofstede (2005); the YAWL system is described in van der Aalst et al. (2004). ter Hofstede et al. (2010) present a comprehensive book about all aspects of the YAWL language, the YAWL system, and related approaches. Graph-based workflow languages are introduced in Leymann and Altenhuber (1994) and Leymann and Roller (1999); workflow applications are considered in Leymann and Roller (1997).

In the context of flexible workflow management, graph-based workflow languages, including their technical aspects like handling of application data, are introduced in Weske (2000). A graph-based workflow language with block structuring is proposed by Reichert and Dadam (1998). In the context of the Unified Modeling Language, Activity Diagrams can be used to represent business processes, as shown in Booch et al. (2005). An early overview of workflow languages is given in Forst et al. (1995); Weske et al. (2005) devote a chapter to workflow language, also discussing service composition languages.

Instantiation of process models is discussed in Decker and Mendling (2009), where BPMN and other process languages are investigated with respect to their instantiation semantics.

The BPMN specification is available by the Object Management Group (2011). A poster explains the key concept of the BPMN in a concise way; more information can be found in BPM Offensive Berlin (2011). A workshop series is devoted to the Business Process Model and Notation; workshop proceedings are available as Mendling et al. (2011) and Dijkman et al. (2011). This notation is also in the centre of Silver (2011), where practical aspects of BPMN are discussed.