BPMN
BPMN, Business Process Model and Notation, is the graphical notation standardised by the Object Management Group for modelling business processes, published as BPMN 2.0.2 and adopted as the international standard ISO/IEC 19510. Three properties define it, and none rests on the number of its symbols: it models a collaboration between independent participants, it treats events as first-class typed objects and its execution semantics are formal enough for a model to be run by a process engine. Its notation unfolds across three levels, from descriptive to executable, each a refinement of the one before.
Goal
BPMN serves to fix, unambiguously, the way a process unfolds: who does what, what triggers each step and what passes from one participant to another, drawn as an object in its own right.
The deliverable ranges from the collaboration diagram, legible to the business, to the executable model that is the specification for a process engine, what sets BPMN apart in process modelling: it can be executed or feed a simulation.
Usage
When to use it
- An interaction crossing an organisational boundary: two independent participants exchange messages, to be modelled as a collaboration of pools.
- A future process intended for automation: the BPMN model becomes the specification a process engine executes.
- Typed events matter: deadlines, triggering messages and error handling must be explicit objects of the model.
- Governance and compliance of hand-overs: the hand-over is drawn as an object, which documents responsibilities and sequences in an auditable way.
- As-is / to-be process improvement: the semantics, who does what and what triggers what, must remain unambiguous.
When not to use it
- One organisation, one chain, binary tests, a non-technical consensus: take the flowchart, with no boundary to cross the pools and messages are decorative.
- Detailing a single software use case, guarded branches and true concurrency inside a system: take the UML activity diagram.
- The question is what constrains and performs a function, not the sequence: take IDEF / IGOE, where rules and resources are structural.
Description
A collaboration between independent participants
A pool is a participant, an organisation that acts on its own account, a capability no other notation in the family has. The distinction with a flowchart does not therefore rest on lanes, a notational addition all four notations accept alike, but on a semantic rule: the only thing that crosses a pool's boundary is a message flow.
Events make explicit what triggers or ends a step; gateways route the flow without deciding it, the decision staying in the preceding task.
| Notation | Sequence or scope? | Messages across an organisational boundary? | Typed events? | Executable by an engine? | Formal semantics? | Swimlanes possible? |
|---|---|---|---|---|---|---|
| Flowchart | sequence | no | no | no | no | yes |
| BPMN | sequence | yes | yes | yes | yes | yes |
| UML Activity Diagram | sequence | no | no | no | yes | yes |
| IDEF / IGOE | scope | no | no | no | yes | n/a: no lanes, no time |
The three modelling levels
BPMN is organised into three nested levels: three conformance sub-classes, Descriptive, Analytic and Common Executable, named levels 1, 2 and 3 by Bruce Silver. Each level refines the one before into a single model. The descriptive level meets most needs, the one the Swiss standard eCH-0158 retains for public administration.
- 1DescriptiveOMG conformance sub-class · Silver level 1
For the business teams that map the process.
The base set: pools and lanes, tasks and sub-processes, sequence and message flows, simple start and end events, exclusive and parallel gateways. The shared, universally legible baseline, what the process is.
- 2AnalyticOMG conformance sub-class · Silver level 2
For the analysts and architects who analyse and improve the process.
Adds the typed events and exception handling: messages, timers and errors, intermediate and boundary events, event sub-processes. The detail that lets you reason about performance and failures.
- 3Common ExecutableOMG conformance sub-class · Silver level 3
For those who automate the process.
Adds the execution detail beneath the diagram: data, expressions, service interfaces. The model becomes the specification a process engine executes.
BPMN describes the flow of control, who does what and in what order. The movement of data across a system is a different question, treated by the data flow diagram.
You'll find more detail in our BPMN tutorial.
AI considerations
An assistant model produces a first descriptive draft from a written procedure, which the session then corrects, and checks a model against conventions, naming, exception paths, rules of the targeted level, mechanical work.
Two decisions cannot be delegated: the boundary of the participants is a stakeholder fact, and the accuracy of what executes is verified against the sources and the engine's real behaviour, never against the plausibility of a generated answer.
Examples
A Swiss SME files its annual payroll declaration with its AVS compensation fund. The concept the drawing makes visible fits in one sentence: a pool is a participant, and the only thing that crosses its boundary is a message flow. The employer and the fund are two separate legal entities, hence two pools, and everything that passes from one to the other is a message.
- Pool = participant
- Sequence flow
- Message flow
The two directions of the exchange are message flows: the employer sends the declaration, the fund returns the statement or a rejection. The rest is internal to each pool. The January deadline is a timer start event. The rejection is a typed end event: the model carries them as objects.
Visualizations
The geometry carries the meaning: a figure that departs from the standard states something false, as verifiable as a text. The three levels read as a stack where each level adds to the one before.
Cost
| Phase | Level | Justification |
|---|---|---|
| Preparation | Medium | Identify the actual participants and gather the people who know the exchanges and deadlines. A descriptive draft needs nothing more than a whiteboard. |
| Execution | Medium | A descriptive collaboration fits in a facilitated session; the analytic level adds typed events and exceptions, the executable level the data and interfaces. |
| Documentation | High | An executable model is versioned with the engine it drives. A descriptive diagram is maintained more cheaply, but loses its value as soon as it diverges from the ground. |
Tooling
A whiteboard is enough for the first descriptive draft. General-purpose drawing tools, Visio, diagrams.net or Lucidchart, carry correct BPMN stencils, but their contribution stops at the image: nothing there guarantees that a gateway is valid.
Dedicated platforms, Camunda, Bizagi, Signavio or the ARIS suite, hold the model as an executable object, validate the syntax and run the process on an engine. A Swiss administration models against the eCH-0158 conventions.
Sources
- OMG, Business Process Model and Notation (BPMN), Version 2.0.2, 2014: the primary standard; its conformance clause (clause 2) defines the three modelling sub-classes, the collaboration clause (clause 9) the pools and message flows, the process clause (clause 10) the sequence flows, activities, events and gateways.
- IIBA, A Guide to the Business Analysis Body of Knowledge (BABOK Guide) v3, §10.35 Process Modelling: the definition, the element list and the recognised limitations of process modelling, including the use of the model as a basis for simulation or execution.
- ABPMP, Guide to the Business Process Management Common Body of Knowledge (BPM CBOK), §3.3.1 BPMN 2.0: the treatment of BPMN among the process-modelling notations and its organisation into descriptive and analytic sets.
- ABPMP, Guide to the Business Process Management Common Body of Knowledge (BPM CBOK), §3.3.2 Swim Lanes: swimlanes are a notational addition and not a distinct notation.
- ISO/IEC 19510:2013, Information technology - Object Management Group Business Process Model and Notation: BPMN adopted as an international standard, the one a Swiss public-sector buyer references in a tender.
- eCH, eCH-0158 BPMN modelling conventions for public administration, V1.2: the Swiss e-government standard that restricts BPMN's options for the public sector, with an emphasis on the descriptive level.
- Bruce Silver, BPMN Method and Style, 2nd edition: the three-level method, built on OMG's conformance sub-classes.
- HERMES 2022, project management method of the Swiss Confederation: BPMN is named there as the notation for the process-modelling result, attributed to the Object Management Group.