BPMN Methodology. Part 2.
Core Components of BPMN
Business Process Model and Notation (BPMN) uses various graphical elements to visualize and model processes.These elements capture different aspects of processes such as activities, decisions, events, and flows between them.Below is a description of the main BPMN components.
Activities
Activities represent specific steps or tasks within a process. They are depicted as rounded rectangles. Several types of activities exist:
- Task: A single action performed by a user, system, or other actor.
- Subprocess: A part of the process that groups multiple activities into a single block. Subprocesses simplify the main process by hiding detailed steps that might otherwise clutter the model.
- Multi-instance Tasks: Tasks performed repeatedly—for example, when the same task must be completed for multiple entities (e.g., approvals from multiple people). These can be either parallel or sequential.
Events
Events represent something that occurs during the execution of a process and may influence its flow. Events are usually shown as circles and come in several types:
- Start Event: Indicates the beginning of a process. Represented by a thin, empty circle.
- Intermediate Event: Occurs during the process and may trigger further actions (e.g., timer, message, error). Displayed as a circle with a double thin line.
- End Event: Marks the completion of a process or a branch. Shown as a circle with a thick border.
Gateways
Gateways are used to split or merge flows within a process. They serve as decision points that determine how the process proceeds. Represented by a diamond shape, several types of gateways exist:
- Exclusive Gateway: Allows selection of a single path from multiple options. Used when only one branch should continue.
- Parallel Gateway: Enables simultaneous execution of multiple flows. The process continues on all following branches concurrently.
- Inclusive Gateway: Allows one or more branches to proceed, depending on specific conditions.
- Event-based Gateway: The process flow is determined by an event, such as waiting for a message or a time limit.
Flows
Flows illustrate the connections between process elements and how the process progresses. There are three main types:
- Sequence Flow: Defines the order of activities and is represented by a solid line with an arrow.
- Message Flow: Shows the exchange of messages between different entities or processes. Used between swimlanes (participants), represented by a dashed line with an arrow.
- Association: Links data objects, notes, or artifacts with activities or events. Shown as a dashed line without an arrow.
Swimlanes
Swimlanes divide process steps among different actors or systems involved in the process. They help visualize responsibility for each activity.
- Pool: Represents a main organizational entity, such as an organization or system.
- Lane: A subdivision within a pool, representing a specific department or role responsible for parts of the process.
Artifacts
Artifacts are supplementary elements that help document and clarify the process:
- Data Object: Represents data used or produced within the process, such as a document, message, or database record.
- Data Store: A location where the process can read or write data, such as a database, spreadsheet, or server.
- Groups: Visually group multiple elements into a logical set without affecting process execution.
- Annotations: Provide additional information about elements in the model to enhance understanding of the context.
These are the essential BPMN components that enable comprehensive and precise process modeling. Each element has its specific purpose and usage rules to ensure that BPMN models accurately reflect real processes and remain understandable to all involved.
Collaboration and Process Diagrams
Collaboration Diagram
A collaboration diagram is a type of BPMN diagram used to model interactions between multiple process participants.It features pools representing participants who exchange messages via message flows.This diagram doesn’t show detailed processes inside each pool but focuses on the main process (typically from the perspective of one participant, e.g., a citizen) and the communication between participants (e.g., with external actors).
Used for:
- Modeling communication between organizations, departments, or systems.
- Visualizing how different entities collaborate toward a common goal.
- Highlighting message exchanges between participants.
When to use:
- To capture interactions among multiple processes or participants.
- To model external interactions (e.g., between a citizen and an institution).
- When you want to show high-level collaboration among stakeholders.
When not to use:
- When you need to model detailed steps within a single process.
- When all processes are within one department or organization (in that case, a process diagram is better suited).
Example of use in modeling life events
Modeling the “Birth of a Child” life event:
- Pool 1: Parent (individual person)
- Pool 2: Authority (public institution)
- Message flows: “Submit birth certificate request,” “Deliver birth certificate”
- This diagram would illustrate how the parent and authority interact during the application process.
Process Diagram
A process diagram focuses on modeling the internal flow of activities within a single process or participant.It includes start and end events, activities, sequence flows, and optionally gateways for decision logic.
Used for:
- Showing detailed steps required to complete a process.
- Visualizing the sequence of activities.
- Capturing the process logic including conditions, exceptions, and parallel flows.
When to use:
- To model the internal logic of a process, such as the steps from order receipt to delivery.
- To analyze or optimize internal procedures.
- To document workflows within one organization or department.
When not to use:
- When the process involves multiple participants and communication among them (then use a collaboration diagram).
- When you need to illustrate message exchanges or interactions between organizations.
Example of use in modeling life events
When modeling the “Birth of a Child” life event, a process diagram could detail the internal procedure of the authority processing the application:
- Start event: “Birth certificate request received”
- Activities: “Verify data,” “Create birth certificate,” “Send birth certificate”
- End event: “Application processed”