BPMN 1.2 tutorial
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Introduction
This article provides a short overview of BPMN 1.2. BPMN is a so-called flowcharting notation language for defining a so-called businnes process in terms of connected activites, events and gateways.
Overview of BPMN 1.1/1.2 (2008/9)
According to the BPMN 1.2 specification, “The primary goal of BPMN is to provide a notation that is readily understandable by all business users, from the business analysts that create the initial drafts of the processes, to the technical developers responsible for implementing the technology that will perform those processes, and finally, to the business people who will manage and monitor those processes. Thus, BPMN creates a standardized bridge for the gap between the business process design and process implementation. Another goal, but no less important, is to ensure that XML languages designed for the execution of business processes, such as BPEL4WS (Business Process Execution Language for Web Services), can be visualized with a business-oriented notation.”
According to the 1.2 specification, BPMN has four categories of core elements for defining a business process:
- (1) Flow Objects
- define the behavior of a business process and are the most important constituant elements of process diagrams.
- Types: Event (start, intermediate, end), Activity (task, sub-process and process), Gateway (various)
- (2) Artifacts (Artefacts)
- are used to provide extra information about the process
- Types: Data Object, Group, Annotation
- (3) Swimlanes
- group elements into processes performed by entities
- Types: Pool, Lane
- (4) Connecting Objects
- connect flow objects and artifacts (above) to each other
- Types: Sequence Flow, Message Flow, Association. Process diagrams can be structured in three ways:
- Sequence flows define an order of activities performed in a process. Each flow has a single source (a start event, activity or gateway) and a single target (a end event, activity of gateway). Elements of a sequence flow are connected with solid arrows.
- Message flows either connect two pools or flow objects within these pools. As opposed to sequence flows, they cannot connect objects within the same pool. Message flows are represented with dashed arrows.
- Associations associate flow objects with information and artifacts and are drawn with dotted lines.
Message and sequence flows are usually drawn orthogonally, i.e. sequence goes in one direction (either top->down or left->right) and messages in the other.
BPMN 1.2 event elements
Events
An event is something that "happens" during a process and it will affect the flow of the process. It usually has either a cause or an impact or both. In more operational terms, events will affect the sequence of the timing of process activities.
There are three main types of events: start events, intermediate events and end events. Events are represented as small circles.
Start Events
Start events indicate the initiation of a process and are usually associated with a trigger. The five types of triggers defined by v. 1.1 are represented with graphical markers.
- Plain (generic) start events
- do not specify any trigger
- Message start events
- start when a message is received from an other participant
- Timer start event
- indicate a given time/date for starting
- Conditional start events
- a process is triggered when certain business conditions become true.
- Signal start events
- A signal arrives that has been broadcasted from another process
- Multiple start events
- Defines multiple ways of triggering a process.
Intermediate events
There are 10 types of intermediate events in BPMN 1.2. All of these can respond to (catch) a trigger and some can set off (throw) a trigger. Catching events (only) also can be directly attached to the boundary of an activity.
Events are drawn as double circle. Catching event markers are drawn with strokes and throwing events are drawn filled.
- Simple ("none") intermedia event
- Events in the main flow of the process that are not further specified.
- Message (catching and throwing) intermediate events
- When catching, a message arrives from a participant and triggers the Event. If the process was waiting for the message it then can continue. Messages also can be used for exception handling, i.e. the process will continue differently.
- When throwing in normal flow, a message is sent to another participant.
- Summarized, messages are used to receive/send between 2 participants A and B.
- Timer (catching) intermediate event
- A set time/date will trigger the event, i.e. also inserts a delay
- Error (catching) intermediate event
- Only can be used in the boundary of an object. Can either catch a named error or all errors if none is specified
- Cancel (catching) intermediate event
- This cancel event must be used in the boundary of a transaction subprocess. It can be triggered either by a message or by a cancel end event in the subprocess.
- Compensation (catching and throwing) intermediate events
- When catching, a compensation activity attached to this event will be triggered.
- In normal flow, when throwing an event is defined, this event will be triggered, else "compensation" is broadcasted to all activities in the process.
- Conditional (catching) intermediate event
- Event is triggered when a condition becomes true
- Link (catching and throwing) intermediate event
- Links connect two sections of a process (at the same level), e.g. to implement looping, goto or simply move to a "next page". There can be multiple source, but only one target link.
- Signal (catching and throwing) intermediate event
- Signals can be sent and received accross process levels, pools and even diagrams. As opposed to messages, targets cannot be identified, i.e. there is always a specific source (throwing) but specific target. In other words, a signal is like a flare. Catching events must be attached to the boundary of an activity.
- Multiple (catching and throwing) intermediate event
- In normal flow, a multiple event can either catch or throw various events. When attached to an activity it can only catch.
End events
- Simple ("none") end event
- showing that and where a process ends
- Message end event
- indicates that a message is sent to a participant when the end of the process is reached
- Error end event
- an error code should be generated. This code then can be caught by an error catching intermediate event in the parent. If there is none, then the system also can handle this.
- Cancel end event
- is only used in transaction sub-processes and will signal that this transaction should be cancelled.
- Compensation end event
- can either compensate an activity that is identified. Otherwise all activities in the process can be subject to compensation if they have a compensation intermediate event attached.
- Signal end event
- a signal is generated. It will be broadcasted to any process (i.e. signal catching events) that can receive it. A signal is different from a message. The latter always has a source and a target.
- Terminate end event
- triggers an immediate end to the process and all its activities. The process is ended without compensation of event handling.
- Multiple end event
- multiple consequences of ending the Process.
Activities
An activity stand for the work that company performs. An activity can be atomic or non-atomic (compound). The types of activities that are a part of a Process Model are:
- Tasks
- Sub-Process
- Process, but these are represented with swimmlanes
Simple tasks
An "atomic" (simple) task is a simple activity performed within an organization. The correspond to a step in the process flow. Tasks and Sub-Processes are represented with rounded rectangles.
Examples
Model of a discussion
Email voting process
Model of surgery programming
The process model presented by Roja et al. (2008) shows at a high level abstraction the programmed surgical patient (PSP) process and the activities that are carried out when a patient is admitted into the hospital for the accomplishment of the surgical treatment of a disease that has been clinically diagnosed previously. This model is a result of a joint work between hospital and BPMN expert and it has been obtained through a reiterative and incremental method.
“The modelling of the programmed surgical patient process and its subprocesses has allowed to us to prepare an understandable model for the involved health professionals and make the communication of processes easier. Additionally, modelling allows early detection and correction of errors. This work is an essential previous step for further analysis and improvements in healthcare processes, including the adoption of information technology standards.” (Roja et al. (2008))
A BPMN 1 meta model
A more difficult to understand meta-model (i.e. an inofficial UML class diagram of BPMN was published by WSPER ("whisper").
Links and bibliography
See BPMN for more links and references
- Dive into BPMN
- Modeling Workflow Patterns through a Control-flow perspective using BPMN and the BPM Modeler BizAgi by Marcus Goetz, Institute of Applied Informatics and Formal Description Methods University Karlsruhe (TH).
- BPMN_Tutorial.pdf by Martin Owen and Jog Raj, Popkin Software