BPMN Diagrams

BPMN (Business Process Model and Notation) diagrams let you model the flow of work across tasks, events, and decision points, optionally partitioned into pools and lanes to show which participant is responsible for each step. The WME BPMN editor follows the definition of BPMN models.

Pools and Lanes

A Pool represents one participant (an organisation, a system, or a role). Drag a Pool from the sidebar onto the canvas to create it. Pools can be resized by dragging their borders.

A Lane partitions a pool into responsibility zones. Drop a Lane inside an existing Pool. Flow nodes placed inside a lane are automatically assigned to that lane’s process; you can re-assign them by dragging them into another lane.

When a diagram has no pools, all flow nodes belong to a single implicit process.

Tasks

Tasks are the basic units of work. Seven concrete types are available in the palette:

  • Default Task: a generic task with no specific marker.

  • User Task: performed by a human actor (person icon).

  • Service Task: executed by a system or service (gear icon).

  • Send Task: sends a message to an external participant (filled envelope).

  • Receive Task: waits for a message from an external participant (empty envelope).

  • Manual Task: carried out without system support (hand icon).

  • Script Task: executes a script (scroll icon).

Double-click any task to rename it. Click the task to open its property popup and change its type or loop characteristics (none / standard loop / parallel multi-instance / sequential multi-instance).

Events

Events mark something that happens during a process. Three positions are available:

  • Start Event: the entry point of a process (thin circle). Drag onto the canvas or inside a pool to create. Supported triggers: none (default), Message, Timer, Conditional, Signal, Escalation, Error, Compensation, Link.

  • Intermediate Event: occurs between start and end (double circle). Catch variants (Message, Timer, Conditional, Signal, Link) and throw variants (Message, Timer, Signal, Escalation, Compensation, Link) are both supported.

  • End Event: the final state of a process (thick circle). Supported results: none (default), Message, Signal, Error, Escalation, Compensation, Terminate.

Click an event to select its trigger or result type in the property popup.

Gateways

Gateways control how sequence flows split and merge:

  • Exclusive (XOR): only one outgoing path is taken (X marker).

  • Inclusive (OR): one or more paths may be taken (circle marker).

  • Parallel (AND): all paths are taken simultaneously (+ marker).

  • Complex: custom merge/split logic (asterisk marker).

  • Event-based: the next event to occur determines the path (pentagon marker).

One outgoing sequence flow may be marked as the default flow (diagonal slash marker) on Exclusive, Inclusive, and Complex gateways, and on any Task. Set it in the flow’s property popup.

Sequence and Message Flows

Sequence flows connect flow nodes within the same process or sub-process. Draw one by hovering over a source element until the blue connection handles appear, then drag to the target.

Message flows connect elements across pool boundaries. They can connect pools to pools, tasks to pools, or tasks to tasks in different pools. Draw them the same way as sequence flows; the editor detects the cross-pool target automatically.

Data Elements

  • Data Object: a piece of data used or produced by a task within a process. Connect it to tasks with Data Associations.

  • Data Store: a persistent data repository shared across the whole model (database cylinder icon).

Artifacts

  • Text Annotation: attach a free-text note to any element via an Association.

  • Group: a dashed rectangle that visually groups elements without affecting flow.

Exporting

To export a BPMN diagram:

  1. Open the diagram in the editor.

  2. Click Export in the top bar.

  3. Select Export as BPMN (.bpmn).

The downloaded .bpmn file is BPMN 2.0.2-conformant and includes Diagram Interchange (DI) information so the layout is preserved when the file is opened in Camunda Modeler, bpmn.io, or any other conformant tool.

Importing

From a BPMN XML file (.bpmn)

  1. Click Import in the top bar.

  2. Select Import BPMN (.bpmn).

  3. Choose a .bpmn file exported from the WME or from another BPMN tool.

The editor reconstructs pools, lanes, all flow node types, sequence and message flows, and DI layout from the file.

From a B-UML Python file (.py)

  1. Click Import in the top bar.

  2. Select Import B-UML (.py).

  3. Choose a .py file generated by the BESSER BPMN generator.

The B-UML import executes the Python source to reconstruct the BPMNModel and converts it to WME JSON. Layout information is not preserved; the editor auto-positions the elements.

Validation

The WME BPMN editor highlights structural issues as you model:

  • Every sequence flow must have a valid source and target within the same container.

  • Message flows must cross pool boundaries.

  • A default flow may only be set on a Task, or on an Exclusive, Inclusive, or Complex Gateway.

  • Each pool must reference exactly one process.

  • Lane membership must be consistent with the enclosing process.

Errors are shown in the validation panel. Warnings (e.g. unreachable flow nodes) are shown separately and do not block export.