BPMN 2.0 Activities

BPMN Activity Basics

An Activity

• is work that is performed within a Business Process
• can be atomic or non-atomic (compound)
• represent points in a Process flow where work is performed
• is executable element of a BPMN

Process.

Activity can be:

• Task
  • an atomic Activity within a Process flow
  • is used when the work in the Process cannot be broken down to a finer level of detail
  • an end-user or applications are used to perform the Task when it is executed
• Sub-Process
• Call Activity
  • allows the inclusion of re-usable Tasks and Processes in the diagram

Types of Tasks

Receive Task

• Waits for a Message to arrive from an external Participant
• Once the Message has been received, the Task is completed

• Starts the process
• MUST NOT have any incoming Sequence Flow
• Instantiate attribute MUST be set to true

User Task

• A typical “workflow” Task where a human performer performs the Task with the assistance of a software application
• The task is scheduled through a task list manager of some sort

Examples:

• Phone operator updates customer record
• User changing their password

Manual Task

• Is expected to be performed without the aid of any business process execution engine or any application

Examples:

• A telephone technician installing a telephone at a customer location

Business Rule Task

• Provides a mechanism for the Process to provide input to a Business Rules Engine and to get the output of calculations that the Business Rules Engine might provide

Script Task

• Is executed by a business process engine
• The modeler or implementer defines a script in a language that the engine can interpret
• When the Task is ready to start, the engine will execute the script
• When the script is completed, the Task will also be completed.

Sub-process Markers

• A Sub-Process is an Activity whose internal details have been modeled using Activities, Gateways, Events, and Sequence Flows
• A Sub-Process is a graphical object within a Process, but it also can be “opened up” to show a lower-level Process

Types of Sub-Processes

Sub-process Markers

Event Sub-Process

• An Event Sub-Process is a specialized Sub-Process that is used within a Process (or Sub-Process)
• The triggeredByEvent attribute is set to true
• An Event Sub-Process is not part of the normal flow of its parent Process—there are no incoming or outgoing Sequence Flows.
• It MAY occur many times.
• Event Sub-Process has a Start Event with a trigger:
  • Message, Error, Escalation, Compensation, Conditional, Signal, and Multiple
• An Event Sub-Process object shares the same basic shape as the Sub-Process object, which is a rounded rectangle

When an Event Sub-Process is triggered the parent Process:

1. can be interrupted
2. can continue its work (not interrupted)

This is determined by the type of Start Event that is used

Transaction

• Is a specialized type of Sub-Process that will have a special behavior that is controlled through a transaction protocol (such as WS-Transaction)
• The boundary of the Sub-Process will be double-lined to indicate that it is a Transaction
• The behavior at the end of a successful Transaction Sub-Process is slightly different than that of a normal Sub-Process
• When each path of the Transaction Sub-Process reaches a non-Cancel End Event(s), the flow does not

immediately move back up to the higher-level parent Process, as does a normal Sub-Process

• First, the transaction protocol needs to verify that all the Participants have successfully completed their end of the Transaction
• Most of the time this will be true and the flow will then move up to the higher-level Process
• But it is possible that one of the Participants can end up with a problem that causes a Cancel or a Hazard
• In this case, the flow will then move to the appropriate Intermediate Event, even though it had apparently finished successfully

Ad-Hoc

• A group of Activities that have no REQUIRED sequence relationships
• A set of Activities can be defined for the Process, but the sequence and number of performances for the Activities is determined by the performers of the Activities.

Call Activity

• A Call Activity identifies a point in the Process where a global Process or a Global Task is used
• The Call Activity acts as a ‘wrapper’ for the invocation of a global Process or Global Task within the execution
• The activation of a call Activity results in the transfer of control to the called global Process or Global Task

Loops

Upstream Sequence Flow

Standard Loop

• The Activity will loop as long as the boolean condition is true
• The condition is evaluated for every loop iteration, and MAY be evaluated at the beginning or at the end of the iteration
• In addition, a numeric cap can be optionally specified
• The number of iterations MAY NOT exceed this cap

Multi-Instance

• The instances MAY execute in parallel or MAY be sequential.
• Either an Expression is used to specify or calculate the desired number of instances or a data driven setup can be used
• In that case a data input can be specified, which is able to handle a collection of data
• The number of items in the collection determines the number of Activity instances
• This data input can be produced by an input Data Association
• The modeler can also configure this loop to control the tokens produced.