Event-driven process chain: EPK definition, rules and examples

The event-driven process chain (EPC) as a graphical model language is used for the systematic representation of business processes. These processes are created using defined syntax rules and a semiformal modeling language. 

In the following article you will get all important information and a definition of the event-driven process chain and relevant symbols and objects. In addition, we name the most important rules of the EPC, explain the extended event-driven process chain and give a concrete EPC example and a guide for EPC creation. 

Table of Contents

1. Event driven process chain easily explained
2. Event driven process chain - EPC definition
3. EPC Symbols & Objects
4. EPC: Rules of the event-driven process chain
5. eEPC - Extended Event Controlled Process Chain
6. EPC example
7. Creating EPC - A Guide
8. EPC: Advantages / disadvantages of the event-driven process chain
9. Frequently asked questions (FAQ) about EPC

Event-driven process chain explained easily

• With the help of an EPC, business processes can be modeled in a simple and structured way. 
• In addition, processes within a company can be optimized and analyzed through visualization. 
• The original idea behind the development was the graphical representation of processes based on certain syntax rules. 
• The unambiguous rules make it possible to model business processes based on logic.
• An EPC consists of the three basic elements event, function and connector. 
• These elements can be connected with each other in different sequences and ensure a multi-layered yet clear overall structure. 
• An EPC must always begin and end with an event. 

Event Driven Process Chain - EPC Definition

The Event Driven Process Chain (EPC) is a graphical model language that is used to systematically represent the business processes of a company or organization. 

The method was developed by August-Wilhelm Scheer in 1992 as an essential part of the ARIS concept. ARIS stands for "Architecture of Integrated Information Systems". Common applications of EPC include process documentation, assignment of responsibilities, activity-based costing, and analysis and optimization of business processes. 

Die grundlegende Idee des Konzeptes liegt darin, Arbeitsprozesse mithilfe von definierten Syntaxregeln und einer semiformalen Modellierungssprache grafisch darzustellen. Grundsätzlich findet die Modellierung eines EPK-Modells von oben nach unten statt. Eine EPK besteht aus drei unterschiedlichen Elementen: 

The basic idea of the concept is to graphically represent work processes using defined syntax rules and a semiformal modeling language. Basically, the modeling of an EPC model takes place from top to bottom. An EPC consists of three different elements: 

• Events, 
• funktions, 
• and connectors. 

Unter einem Ereignis versteht man das Eintreten eines betriebswirtschaftlichen Zustandes, der eine Aktivität auslöst. Dagegen ist eine Funktion eine Aktivität, die ein Ereignis auslöst. Die drei logischen Konnektoren (UND, ODER und XOR) verbinden Ereignis und Funktion miteinander. 

An event is the occurrence of a business condition that triggers an activity. In contrast, a function is an activity that triggers an event. The three logical connectors (AND, OR and XOR) link event and function. 

An EPC must inevitably begin with an event and end with an event. Essential aspects are the representation of the control flow, the representation of concurrency / parallelism of conditional branches and loops, as well as the reproduction of the data flow.

In the case of the extended event-driven process chain (eEPC), the organizational units and information systems involved are also specified. An EPK is not predestined for a formal illustration, since properties for a transformation into another notation are not given. 

EPC Symbols & Objects

In addition to the three elementary components of any EPC already mentioned, there are other important EPC symbols and objects. In the following, in addition to function, event and connectors, we also explain connection arrows, AND link, OR link (inclusive OR), XOR link (exclusive OR) and process signpost. The Organizational Unit and Information Object objects are exclusive to eEPC.

Function

A function specifies what happens or should be done after a triggering event (Ex: "Process order"). Each activity to be performed in and during a business process must be modeled as a function. Each EPC must contain at least one function. A function is capable of having a maximum of one input and two outputs / two inputs and one output. 

Event

In an EPC, an event represents a relevant state for business management and information technology (e.g. "order received"). It is an occurred state within a business process. As a rule, it is followed by further process steps. 

Events are significant elements for the control of an organization or a company. Normally, a process chain begins and ends with an event. Function and event usually occur alternately, but there is usually a connector in between. An event may have a maximum of one input and two outputs / two inputs and one output. 

Connection arrows

A connector arrow indicates the flow of an EPC. As a rule, an EPC runs from top to bottom and is represented in this way. The connecting arrow is a directional arrow that connects two elements. 

Connectors

Connectors are logical links between functions and events. Here we distinguish between the three different connectors ("OR", "AND" and "XOR"). All connectors may have either only one input line but several output lines, or only one output line but several input lines. 

AND connector:

An AND connector specifies that all functions or events must occur to trigger the subsequent event or function. 

OR connector (inclusive OR)

The OR connector specifies that at least one event or function must occur (but more than one may occur) for the subsequent event or function to be triggered. 

XOR connector (exclusive OR):

The XOR connector specifies that at least exactly one event or function may occur to trigger the subsequent event or function.

Organizational Unit (eEPC):

The organizational unit indicates which person performs a function. An organizational unit can only be associated with one function.

Information object (eEPC):

Informationsobjekte geben die Daten an, die für die Durchführung einer Funktion notwendig sein. Ein Informationsobjekt kann nur mit einer Funktion verbunden werden.

Information objects specify the data that is required to perform a function. An information object can only be associated with one function.

Process signpost:

A process signpost makes it possible to link individual business processes.

EPC: Rules of the event-driven process chain

In order to guarantee the smooth flow of an event-driven process chain, certain rules must be observed. These rules apply partly in general, partly they refer explicitly to certain EPC symbols or objects.

General rules:

• Only the following symbols can be present in an EPC: events, functions, process route signs, logical links (AND, OR, XOR), organizational units, information objects.
• Relationships are valid if they are directly connected to your previous symbol or indirectly via relationships and lines.
• Basically, an EPC can only start or end with an event or a process route.
• An EPC must have at least one function.
• Symbols must be connected by lines.
• Events cannot be directly connected to other events.
• Functions cannot be directly connected to other functions.

Functions:

• A function cannot precede another function or a process route sign.
• A function can neither follow a process signpost nor another function. 
• Functions must follow at least one event or stand before at least one event.
• A function can have only one input line.
• A function can have only one output line.

Events:

• Events must not precede other events.
• Events may not directly follow other events.
• An event precedes or follows a function.
• An event can have only one input line.
• An event can have only one output line.

Process signposts:

• A process waypoint must precede an event or follow at least one event.
• A process signpost cannot precede a function or another process signpost.
• A process signpost can have only one input line.
• A process signpost can have only one output line.

Link operators

• Are not allowed to stand alone. 
• Are there to link symbols together.
• Are there to create forks in a process chain.
• Link operators must have one incoming arrow and at least two outgoing arrows when splitting a process chain.
• They must have at least two incoming arrows and one outgoing arrow when merging a process chain.
• "OR" or "XOR" operators representing a bifurcation of the process chain must not follow an event.  

Organizational Units (eEPC):

• Organizational units are assigned to functions by dashed lines or are in the same line of a function.
• Organizational units describe jobs.
• They are based on the organization chart of an organization or a company.

Information objects (eEPC):

• Information objects can be linked to functions using arrows.
• The arrows between a function and an information object (IO) describe data flows:
• IO → function describes the input data flow ("read").
• IO ← function describes the output data flow ("write")
• IO ↔ Function describes the process of data being read from the IO to the function, processed, and then returned from the function to the IO ("Read-Write").

eEPC - Extended Event Driven Process Chain

The extended event-driven process chain (eEPC) is, as the name suggests, an extended version of the EPC modeling language. As with EPC, eEPC is used to systematically capture business processes in companies or organizations. In addition to the already known symbols of the EPC, the eEPC is supplemented by further elements, such as an organizational unit and an information object. 

The application areas of the eEPK and the event-driven process chain overlap. The choice of the two modeling languages depends on whether the organizational unit or the information used for the representation is to be modeled. If the modeling of these two elements is required, users will need to resort to the extended event-driven process chain.

An extended event-driven process chain, like an EPC, serves the needs of non-formal practices. Basically, an eEPC maps parallel sequences of branches and loops or the representation of the control flow. It also reflects the flow of data and indicates which organizational units and information objects take place amid an eEPC. 

Extended event-driven process chains consist of standardized symbols and elements. However, they are not suitable for a formal representation because they cannot be converted into formal notations. 

EPC Example

An EPC example could be the following, visualized in the following. 

• Incoming order: Company XY first commissions clous to perform a tolerance determination. 

• The EPC starts with the order being received by clous and checked in the process flow. 
• Now the question arises whether clous accepts or rejects the order. Here, only one of the two events can occur. 
• If clous accepts the order, it will be processed and finally completed. 
• If clous rejects the order, the order is sent back to the client.

Creating EPC - A Guide

The following guide makes it easy to create an event-driven process chain. 

1. The first step is to identify the problem. Then decide which process should be modeled.
2. The next step is to create a complete list of all possible events and functions. It is not necessary to follow a chronological order.
3. In this step, both the beginning and the end of the process are defined. With regard to the predefined rules, each is an event.
4. Now the created list of events and the functions is put into an ordered temporal sequence.  
5. Once the order is established, the next step is to select the correct connectors. The final result comes from the complete sequence of event, function and connector.
6. Next, one selects a suitable tool to model the event-driven process chain. Examples are Microsoft Powerpoint or Lucidchart.
7. After choosing the appropriate tool, all symbols for the events, functions and connectors have to be created.
8. The final step is to arrange all the symbols into a finished EPK in the correct order.

EPC: Advantages / disadvantages of the event-driven process chain

As with pretty much everything, EPCs have specific advantages and disadvantages. In the following, we briefly discuss some of them.

Advantages EPC

Event-driven process chains are characterized in particular by their easy readability as well as their user-friendly operability. The user-friendly modeling language enables people who are not IT experts to quickly understand and learn it. 

An EPC can be analyzed accurately due to the visualization of the process, the simple clarity and the intuitive comprehensibility. Furthermore, these characteristics form the basis for learning how to analyze and represent an EPK. An accurate representation of processes can be implemented through an EPC. The fact that an EPC is a quasi-industry standard underlines this. 

EPCs are offered by various applications and supported by a wide range of tools. Thus, there are many possibilities to create EPCs easily and without much effort. A clear visualization of the dependency of events and functions is much easier compared to other representation methods. 

The few and unambiguous rules ensure that the creation of an EPK involves little work. The status of a process is consistently transparent due to the sequence of an event on a function.

Disadvantages EPC

EPCs have a shortcoming in the trainability of creative and complex processes. In addition, the representation of monitoring activities is problematic and cannot be easily mapped.

Whether the rule of having an event follow a function is actually useful can be questioned upon closer examination. Compared to an eEPC, an EPC neglects the person performing the activity. In addition, EPCs do not show how long the waiting times or throughput times of a process are. 

Finally, there is the possibility that the top-down modeling leads to a confusing representation and confuses the viewer.

Frequently asked questions (FAQ) about the EPK

What is an EPC?

With the help of an event-driven process chain (EPK), business processes can be logically captured and visually represented. Furthermore, an EPC is a modeling language that is used for the previous purposes. The classic elements and symbols of an EPC represent events, functions and link connectors. In the application case, EPCs are usually used for process documentation or for the analysis and optimization of processes in companies. 

How is an EPC structured?

Basically, an EPC begins and ends with an event. The structure of an EPC follows the top-down principle and is therefore read from top to bottom. An event is followed by a function. These two elements are connected by a logical connector. 

How is an EPC model created?

An EPC is first created by thinking about the desired process. Then one writes an unordered list of all possible events and functions and considers all necessary connectors. Then a desired sequence is determined and a tool for modeling is selected. Finally, all symbols are finalized and the EPK is arranged in the desired order.

What is the difference between EPK and eEPK?

EPC and eEPC have little to no differences. As the name implies, the extended event-driven process chain is simply an extension of the existing modeling language. The only notable difference is the two added elements of "organizational unit" and "information object".