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Thinking in Diagrams

BPMN

Processes & experienceField guide · Processes & experience · 3 of 6

What happens, precisely enough that it could be run?

BPMN, Business Process Model and Notation, is the Object Management Group’s standard for drawing a process as tasks, gateways and events in pools and lanes, each mark defined exactly enough that an engine can run an executable process drawn in it.

Marks

Section titled “Marks”
MarkDrawn asStands forSource
taska rounded box, thin-lined, its name insideone unit of workp. 154
A task in BPMN: a rounded box A rounded box: log the report. log thereport
gatewaya diamond, an X inside an exclusive onewhere paths split or join; at an exclusive one, one path is takenpp. 286, 289
An exclusive gateway in BPMN: a diamond with an X inside A diamond with an X inside, labeled repair needed? beneath it. repair needed?
sequence flowa solid line with a solid arrowheadthe order of the work, within one poolpp. 21, 95
A sequence flow in BPMN: a line with an arrowhead A rounded box: schedule the repair. Its sequence flow, a line with an arrowhead, runs right to a rounded box: fill the pothole. schedulethe repair fill thepothole
poola rectangle, named in a band at its sideone participantp. 111
A pool in BPMN: a rectangle named in a band at its side A rectangle, named town council in a band at its left, holding a rounded box: log the report. towncouncil log thereport
lanea band within a pool, named at its sidea role, system or departmentpp. 304–305
Two lanes in BPMN: bands within a pool, each named at its side One pool, named town council in a band at its left, holding two lanes, one above the other, each named at its left: customer services, with a rounded box, log the report; highways inspector, with a rounded box, inspect the road. towncouncil customerservices highwaysinspector log thereport inspectthe road
start event; intermediate eventa thin circle; a double thin circlewhere the process starts; something happening during itpp. 237, 249
A start event and an intermediate event in BPMN: a thin circle and a double thin circle A thin circle, a start event, labeled pothole reported beneath it; a double thin circle, an intermediate event, labeled repair booked beneath it. pothole reported repair booked
end eventa thick circlewhere a path ends; not in the figure, which is drawn at one width, so no start event either, which requires an end eventpp. 245–246
message flowa dashed line from a small open circle to an open arrowheada message between two pools; not in the figure, since a dash means hypothesis in this bookp. 119
call activitya thick-bordered rounded boxa reused process or task; not in the figurep. 154
remark; marks of one kindwords in an open bracket, joined by a dotted line; a dashed rounded box around themnot in the figurepp. 65–66, 69

A line with an arrowhead

Section titled “A line with an arrowhead”

A sequence flow means then: the task at its head is done next, within one pool. A message flow, between two pools, carries what one participant sends another. Whereas an effect produces a change in the variable at its head, a sequence flow only orders two tasks, and a message flow only moves a message.

A resident reporting a pothole

Section titled “A resident reporting a pothole”
A resident reporting a pothole to the town council, in BPMN One pool, named town council in a band at its left, holding three lanes, one above another, each named at its left with no line between its name and its tasks: customer services, highways inspector, repair crew. Tasks are rounded boxes, joined in order by sequence flows, lines with arrowheads; no event is drawn. In customer services, a task: log the report; its sequence flow runs down into the highways inspector's lane to a task: inspect the road, whose sequence flow runs right to a gateway, a diamond with an X inside, labeled repair needed? Its sequence flow marked no runs up into customer services to a task: tell the resident why not, where that path ends. Its sequence flow marked yes runs right to a task: decide how urgent, whose sequence flow runs down into the repair crew's lane to a task: schedule the repair, whose sequence flow runs right to a task: fill the pothole, whose sequence flow runs up into customer services to a task: tell the resident it is fixed, where that path ends. towncouncil customerservices highwaysinspector repaircrew log thereport inspectthe road repair needed? no tell theresidentwhy not yes decide howurgent schedulethe repair fill thepothole tell theresident itis fixed

Customer services logs the report, and after the highways inspector’s gateway it goes one of two ways: back to customer services to tell the resident why there will be no repair, or on to the repair crew. Each path ends at a task with no sequence flow out of it, valid where no events are drawn (p. 246).

When to draw one

Section titled “When to draw one”

Draw one where a process is to be run by an engine, or documented exactly, in as much detail as chosen, for others to build, check or take over: BPMN 2.0.2’s executable and non-executable processes (p. 21).

When not to draw one

Section titled “When not to draw one”

A process map does for a process no one will run, build from or take over. Organizational models, functional breakdowns, data models, strategy and business rules are outside what BPMN covers, and it is not a data flow language (§7.2, p. 20).

Reasoning and polish

Section titled “Reasoning and polish”
  • Reasoning5 of 5
  • Polish4 of 5one-pool process → executable process
  1. Tasks, sequence flows and one exclusive gateway in one pool
  2. Pools, messages, timers and subprocesses
  3. Events attached to a task, transactions, choreography, and conformance
Section titled “Related types”
  • In BPMN, steps, decisions and their order are drawn as on a process map, in a notation defined formally enough that some diagrams can be run by software.
  • BPMN’s swimlanes are of two kinds, a band for each participant and lanes within it, where a swimlane diagram has a lane for each party.
  • Diagrams of the work behind a service blueprint can be drawn in BPMN, a more internally focused notation, and referred to from the blueprint.

Sources

Section titled “Sources”
  • Object Management Group, Business Process Model and Notation (BPMN), version 2.0.2, formal/13-12-09 (January 2014), the source of every page number here, on every mark above and its drawing, executable and non-executable processes (§7.2.1), what a sequence flow and a message flow connect, optional start and end events (pp. 238, 246), and what BPMN leaves out (§7.2).