BPMN 2.0 Element Guide

Events are triggers that start, modify, or complete a process. Events are shown by circles containing other symbols based on event type. There are three types of events:

Start Event Symbol

Intermediate Event Symbol

End Event Symbol

Events can be either catching or throwing.

Catching events

A catching event is any event that reacts to an external trigger. Something is started once the trigger is activated, such as:

• A process starting

• A process or process path continuing

• A task processing

• A sub-process being canceled

• Another process being used while a task or sub-process executes

Throwing events

A throwing event is any event that the process triggers itself, such as:

• During the process

• At the end of the process

An activity, or task, is defined by a particular action required. Activities and tasks are shown by rectangles with rounded corners:

Task Symbol

Subtask Symbol

Tasks

There are several different task types, as described in the following table:

Task	Description
Receive	Receiving a message can be modeled as a separate task. This task type is an alternative to the catching message event, which is why the symbol for the event defined in BPMN 2.0 is an empty envelope.
Receive (instantiated)	An instantiated task replaces the message start event, and is shown by a small event symbol in the top left corner of the symbol.
Script	Scripts execute directly in the process engine, and must be written in a language that the process engine can interpret.
Manual	A task executed by a user. The task can be executed by any user with access to the process.
Service	A task that is completed by a piece of software. An example is an accounting piece of software that processes pay roll.
User	A task executed by an assigned user.
Send	Tasks that are executed by a web call, or some web service. Typically very technical, and not often used.
Business rule	A task that applies a business rule.

Sub Process versus Call Activity

A call activity is visualized as a rounded task rectangle with a thick border and is used to execute another process definition as part of the current process instance. A call activity does not share context with the process instance. Process variables are explicitly mapped between the process instance and the call activity. The main use case for the call activity is to have a reusable process definition that can be called from multiple other process definitions.

To reference a process using call activity, use the wrench icon from the sub-menu in edit mode to explicitly link to another process. You can then navigate to the linked process when viewing the process model.

A sub process is a single activity that contains activities, gateways, and events which form a process. A sub process is completely embedded inside a parent process. You can use a sub process to create a new scope for events. Events that are thrown during execution of the sub process, can be caught by Boundary events on the boundary of the sub process, creating a scope for that event limited to just the sub process. Sub-processes have the following characteristics:

• A sub process has exactly one none start event. No other start event types are permitted. A sub process must have at least one end event.

• Sequence flow cannot cross sub process boundaries.

• A sub-process is visualized as a rounded rectangle with a minus box within it.

Gateways are decision points in your process that can change the path of the process based on conditions or events. They are shown as diamonds in the process model, and have several types:

Exclusive	Also referred to as an “either/or” decision, this is the most common type of decision in a business process. Exclusive gateways limit the possible outcome of a decision to a single path, and circumstances choose which one to follow.
Event -based	Event-based gateways are similar to exclusive gateways as both involve a single path in the process flow. In the case of an event-based gateway, however, you evaluate which event has occurred, not which condition has been met.
Parallel	To express parallel flow in BPMN, you use a parallel gateway. A splitting parallel gateway takes one input and has several outgoing flows that run at the same time. A joining parallel gateway takes multiple inputs and waits for them all to complete before continuing as a single outgoing flow.
Inclusive	Allows for parallel execution and decision-based exclusion of following sequence flows.
Exclusive (event based)	Event-based gateways and exclusive gateways function in a similar way. Users follow only one path of several potential outbound options. Event-based gateways are only triggered on intermediate events, and they wait for the event to occur before they trigger a decision. Event-based gateways only consider the first event that occurs.
Complex	Complex gateways are only used for the most complex flows in the business process. They use words in place of symbols and, therefore, require more descriptive text. Use complex gateways if you need multiple gateways to describe the business flow; otherwise, you should use an exclusive or inclusive gateway.
Inclusive (event based)	Event-based gateways and inclusive gateways function in a similar way. For inclusive gateways all outbound paths are followed, but are triggered on intermediate events.

Flows show the order of operations within a process model. There are two types of flows depicted:

Sequence flow	Shows the order of activities to be performed. It is shown as a straight line with an arrow. It might show a conditional flow, or a default flow.
Message flow	Depicts messages that flow across “pools,” or organization boundaries such as departments. It shouldn’t connect events or activities within a pool. It is represented by a dashed line with a circle at the start and an arrow at the end.

A pool represents major participants in a process. A different pool may be in a different company or department but still involved in the process.

Swim lanes within a pool show the activities and flow for a certain role or participant, defining who is accountable for what parts of the process.

Artifacts are additional information that developers add to bring a necessary level of detail to the diagram. There are three types of artifacts:

Data object	Shows what data is necessary for an activity.
Groups	Helps organize tasks or processes that have related value in the overall process. Groups help to better arrange your BPMN diagram and increase its readability and value.
Annotation	Allows you to describe the business process and flow objects in more detail. Annotations help make your BPMN more readable and further increase understanding of your process with end users.

Use the following tools to help build and update your process models.

Hand tool		This tool enables you to drag and drop an already placed element. By default, the hand tool is activated.
Lasso tool		This tool allows you to click and drag across several elements and select them.
Space tool		This tool allows you to add or remove space to the canvas.
Connector tool		This tool allows you to draw different types of connections to different elements or pools.
Start event		This element marks the start of the process.
Intermediate event		This element marks a secondary or intermediate step in the process.
End event		This element marks the end of the process.
Create gateway		This element marks a point in the process that could move in different directions depending upon the action needed.
Task		This element marks that a task is required for the event.
Subtask		This element marks a subtask for an existing task in the process.
Data object		This element marks that a task or event might require a script or development process.
Storage		This element marks a storage or data event that might require access to a specific database.
Pool		This element allows you to create a pool that groups specific elements into a process that is part of a larger process.
Group		This element groups surrounded elements into a group boundary.

 

Changing element sub-type

After you have added an element to the canvas, click the Wrench icon to access a sub-menu that allows you to quickly change the element's sub-type without needing to delete or remove the icon. For example, if you added a Task element to the canvas, but it needs to be changed to a Sub-task element, you can change this using the sub-menu from the Wrench icon.