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Connecting Objects

What Connecting Objects Are

In BPMN 2.0, connecting objects define the relationships and flow of information between elements in a process model. They link activities, events, and gateways, guiding the process flow or conveying data and messages. The primary connecting objects are sequence flows, message flows, and associations.

Sequence FlowSequence Flow
Message FlowMessage Flow
AssociationAssociation

Sequence Flow

A sequence flow defines the order in which activities, events, and gateways are performed in a process. It shows the logical progression of tasks from one step to the next.

ProcessMind BPMN sequence flow arrow for process order

This represents the order in which tasks should be executed, shown as a solid line ending with an arrowhead. It can indicate a conditional or default pathway.

  • Example: A sequence flow connects a “Submit Application” task to a “Review Application” task, showing that the review follows the submission.
  • Types of Sequence Flows:
    • Normal Sequence Flow: The default flow between activities.
    • Conditional Sequence Flow: A sequence flow that only proceeds if a specific condition is met (indicated by a small diamond).
    • Default Sequence Flow: The fallback flow if no conditions are met (indicated by a diagonal slash at the starting point).
  • Use Case: Use sequence flows to guide the step-by-step progression of a process, ensuring activities are executed in the correct order.

Message Flow

A message flow represents communication between different participants or processes, typically when they are part of different pools. It is used to show the exchange of information between processes, which might be operating independently.

ProcessMind BPMN message flow for communication between pools

The message flow connector shows communication between different pools or across organizational boundaries, such as departments. It is not intended for linking events or activities within the same pool. This connector is represented by a dashed line, starting with a circle and ending with an open arrowhead.

  • Example: A message flow connects a “Send Invoice” task in one pool (the supplier) to a “Receive Invoice” task in another pool (the customer), showing that the invoice is sent between them.
  • Use Case: Use message flows to illustrate communication between different entities or business participants, such as when one company sends an order request to another.

Association

An association connects artifacts (such as data objects, text annotations, or groups) with flow objects (activities, events, gateways) to provide context or clarify relationships. Associations do not impact the sequence of the process but are used for documentation and additional details.

ProcessMind BPMN association line for linking artifacts and flow objects

This element is shown as a dotted line without an arrowhead or circle. It links an event, activity, or gateway with an artifact.

  • Example: An association connects a “Generate Report” task to a “Report Document” (a data object), showing that this task produces the document.
  • Types of Associations:
    • Normal Association: Connects elements like tasks to data objects or annotations.
    • Directional Association: Shows the flow of data from or to a task (indicated with an arrow).
    • Bi-Directional Association: Indicates two-way relationships between elements (shown with two arrowheads).
  • Use Case: Use associations to link additional information, such as data objects or text annotations, to tasks or events without affecting the process flow.

Associations in exported BPMN files

Associations are exported as standard bpmn:association elements together with the artifacts they link, so they survive a round trip through export and import. A link between an activity and a data object or data store is the exception: it is written as that activity’s bpmn:dataInputAssociation or bpmn:dataOutputAssociation, which is why its direction survives. ProcessMind does not model association direction on plain associations: a directional or bi-directional association from an imported file comes back as a plain association.

Example

Imagine a process for managing customer orders:

  • Sequence Flow: After receiving an order, the system processes the order and then sends it for delivery. Each step (receiving, processing, delivering) is connected by sequence flows.
  • Message Flow: Once the order is processed, a message is sent to an external shipping company to handle delivery. This communication is represented by a message flow between the two entities.
  • Association: A “Customer Order” data object is associated with the “Receive Order” task to show that this task deals with order data.

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