Activiti BPMN elements

The simple diagrams that BPMN consists of to represent the business workflow prove to be helpful for both business users and developers. The four basic categories of BPMN elements are as follows:

1. ‹‹ Flow objects
2. ‹‹ Connecting objects
3. ‹‹ Swim lanes
4. ‹‹ Artifacts

Flow objects

Flow objects consist of various shapes that represent the core elements of business process representation, which characterize the behavior of a business process. To represent the flow of the object, three elements are used: events, activities, and gateways.

• Events :Events can be considered as the actions that occur during the business process. They are represented using a circle in a business process diagram. An intermediate event is represented using concentric circles. There are three types of events: start, intermediate, and end.
• The start event : The start event indicates the start of your business process. It is represented using a single circle. In your business process, you should have only one start event. The start event can be represented as follows:
• Intermediate event : Intermediate event refers to the events taking place between the start and end of the business process. These events do not affect the business process as they do not start or terminate the business process. You can have n number of intermediate events within your business process. The intermediate events are represented using concentric circles, as follows:
• The end event : The end event is represented using a thick-bordered circle as follows, and indicates the end of your business process; there should be at least one end event within your business process:

• Activities : Activities represent the tasks or work that is being performed within a business process. The shape that represents the activities in a BPMN is a round-cornered rectangle. There are various types of activities, such as task, Sub-Process, and the call activity. 
• Task : A task activity is used in a business process when there is an activity to be implemented within a process. It is represented by a round-cornered rectangle. Tasks can be used when there are some actions to be performed in your business process. Various types of tasks  are provided by BPMN, such as the script task, user task, service task, and mail task. A task is represented as follows: The following are the different types of tasks:
• Script task: This task is used for the automation of a task. We can have our logic     implemented here.
• User task: This task can be used in a business process when human interaction is     required for the business, for example, when details are to be filled or verified by   a human. 
• Mail task: This is a type of service task that has services implemented to send e-mails or notifications from the process.
• Service task: This refers to a custom task in which you want some specific operations to be done. Similar to the mail task, which is a type of service task that is used to send e-mails from the process, we have a custom service written for the process.

• Sub-Process : A Sub-Process is a task that is used to represent levels within our business process. This task is useful when we want to display the leveled diagram of a business process. A Sub-Process will be represented as follows:

• The call activity : With the help of the call activity, we can re-use a global process or task that is available within the process engine. On executing the call activity, the control of execution is transferred to the global process or task. A call activity is represented as follows: