Event-driven process chain

An Event-driven Process Chain (EPC) is a type of flowchart used for business process modelling. EPC's can be used for configuring an enterprise resource planning (ERP) implementation,[1] and for business process improvement.

Contents

Overview

Businesses use EPC diagrams to lay out business process work flows, originally in conjunction with SAP R/3 modeling, but now more widely. There are a number of tools for creating EPC diagrams, ARIS Toolset of IDS Scheer AG,[2] (Now taken over by Software AG [3]), free modeling tool ARIS Express by IDS Scheer AG , ADONIS of BOC Group,[4] Mavim Rules of Mavim BV,[5] Business Process Visual ARCHITECT of Visual Paradigm, Visio of Microsoft Corp., Semtalk of Semtation GmbH, or Bonapart by Pikos GmbH. Some but not all of these tools support the tool-independent EPC Markup Language (EPML) interchange format. There are also tools that generate EPC diagrams from operational data, such as SAP logs. EPC diagrams use symbols of several kinds to show the control flow structure (sequence of decisions, functions, events, and other elements) of a business process.

The EPC method was developed within the framework of ARIS by Prof. Wilhelm-August Scheer at the Institut für Wirtschaftsinformatik at the Universität des Saarlandes in the early 1990s.[6] It is used by many companies for modeling, analyzing, and redesigning business processes. As such it forms the core technique for modeling in ARIS, which serves to link the different views in the so-called control view, which will be elaborated in section of ARIS Business Process Modeling.

To quote from a publication on EPCs:[7] "An EPC is an ordered graph of events and functions. It provides various connectors that allow alternative and parallel execution of processes. Furthermore it is specified by the usages of logical operators, such as OR, AND, and XOR. A major strength of EPC is claimed to be its simplicity and easy-to-understand notation. This makes EPC a widely acceptable technique to denote business processes."

The statement that EPCs are ordered graphs is also found in other literature, but is probably a misformulation: an ordered graph is a(n undirected) graph with an explicitly provided total node ordering, while EPCs are directed graphs for which no explicit node ordering is provided. No restrictions actually appear to exist on the possible structure of EPCs, but nontrivial structures involving parallelism have ill-defined execution semantics; in this respect they resemble UML activity diagrams. Several scientific articles are devoted to providing well-defined execution semantics for general EPCs.[8][9] One particular issue is that EPCs require non-local semantics,[10] i.e., the execution behavior of a particular node within an EPC may depend on the state of other parts of the EPC, arbitrarily far away.

In the following the elements used in EPC diagram will be described:

Elements of an event-driven process chain

Event 
Events are passive elements in EPC. They describe under what circumstances a function or a process works or which state a function or a process results in. Examples of events are "requirement captured", "material on stock", etc. In the EPC graph an event is represented as hexagon. In general, an EPC diagram must start with an event and end with an event.
Function 
Functions are active elements in EPC. They model the tasks or activities within the company. Functions describe transformations from an initial state to a resulting state. In case different resulting states can occur, the selection of the respective resulting state can be modeled explicitly as a decision function using logical connectors. Functions can be refined into another EPC. In this case it is called hierarchical function. Examples of functions are "capture requirement", "check material on stock", etc. In the EPC graph a function is represented as rounded rectangle.
Organization unit 
Organization units determine which person or organization within the structure of an enterprise is responsible for a specific function. Examples are "sales department", "sales manager", "procurement manager", etc. It is represented as an ellipse with a vertical line.
Information, material, or resource object 
In the EPC, the information, material, or resource objects portray objects in the real world, for example business objects, entities, etc., which can be input data serving as the basis for a function, or output data produced by a function. Examples are "material", "order", etc. In the EPC graph such an object is represented as rectangle.
Logical connector 
In the EPC the logical relationships between elements in the control flow, that is, events and functions are described by logical connectors. With the help of logical connectors it is possible to split the control flow from one flow to two or more flows and to synchronize the control flow from two or more flows to one flow.
Logical relationships
Control flow 
A control flow connects events with functions, process paths, or logical connectors creating chronological sequence and logical interdependencies between them. A control flow is represented as a dashed arrow.
Information flow 
Information flows show the connection between functions and input or output data, upon which the function reads changes or writes.
Organization unit assignment 
Organization unit assignments show the connection between an organization unit and the function it is responsible for.
Process path 
Process paths serve as navigation aid in the EPC. They show the connection from or to other processes. The process path is represented as a compound symbol composed of a function symbol superimposed upon an event symbol. To employ the process path symbol in an EPC diagram, a symbol is connected to the process path symbol, indicating that the process diagramed incorporates the entirety of a second process which, for diagramatic simplicity, is represented by a single symbol.

Example

As shown in the example, customer order received as the initial event, which creates a requirement capture within the company. In order to specify this function, sales is responsible for marketing, currency etc. As a result, event 'requirement captured' leads to another new function: check material on stock, in order to manufacture the productions. All input or output data about material remains in the information resource. After checking material, two events may happen-with or without material on stock. If positive, get material from stock; if not, order material from suppliers. Since the two situations cannot happen at the same time, XOR is the proper connector to link them together.

Meta-model of EPC

Although a real process may include a series of stages until it is finished eventually, the main activities remain similar. An event triggers one function; and a function will lead to one event. Meanwhile, an event may involve one or more processes to fulfill but a process is unique for one event, the same goes for Process and Process Path. As for the function, its data may be included in one or more information resources, while Organization Unit is only responsible for one specific function.

References

  1. ^ Bart-Jan Hommes (2004). The Evaluation of Business Process Modeling Techniques. TU Delft. p.137.
  2. ^ IDS Scheer AG
  3. ^ Software AG
  4. ^ BOC Group
  5. ^ Mavim BV
  6. ^ A.-W. Scheer (2002). ARIS. Vom Geschäftsprozess zum Anwendungssystem. Springer. p.20.
  7. ^ Anni Tsai et al. (2006). "EPC Workflow Model to WIFA Model Conversion". In: 2006 IEEE International Conference on Systems, Man, and Cybernetics, Taipei, Taiwan, pp. 2758-2763]
  8. ^ Wil van der Aalst (1999). Formalization and Verification of Event-driven Process Chains. In Information & Software Technology 41(10), pp. 639-650
  9. ^ Kees van Hee et al. (2006). "Colored Petri Nets to Verify Extended Event-Driven Process Chains". In Proc. of the 4th Workshop on Modelling, Simulation, Verification and Validation of Enterprise Information Systems (MSVVEIS06), May 23–24, 2006 Paphos, Cyprus, pp. 76-85.
  10. ^ Ekkart Kindler (2006). On the Semantics of EPCs: A Framework for Resolving the Vicious Circle. Technical Report. Computer Science Department, University of Paderborn, Germany.

External links