BPMN: Business Process Modeling and Notation

Business Process Modeling and Notation (BPMN)

• BPMN 1.0 was proposed in May 2004, and adopted by the Object Management Group in February 2006
• The current version is BPMN 2.0 and is based on a revision of other notations and methodologies
• The primary goal of BPMN is to provide notation readily understandable by all business users
• BPMN standardizes the notation used by business experts and IT specialists to bridge the gap between them

Business Process Modeling and Notation Core Elements

• Process diagrams (business process diagrams) are at the core of BPMN modeling.
• There are five core element categories for implementing the properties of business process diagrams
• Flow objects
• Data/information
• Connecting objects
• Swim lanes
• Artifacts

Flow Objects

• Main graphical elements of BPMN that define the behavior of a process
• There are three types of flow objects:
  • Event (displayed as a circle)
  • Activity (displayed as a rectangle with rounded corners)
    • Activities can be further subdivided into 'tasks' and 'subprocesses'
  • Gateway (displayed as a diamond)
• Events come in three basic forms:
  • Start event indicates where a particular process starts
  • End event indicates where the process ends
  • Intermediate event occurs between the start and end-event, used to respond to a trigger
• Activity is a step in a process that performs work
  • There are three types of activities: process, sub process, task
    • A task is an atomic activity
    • Processes and subprocesses are non-atomic entities
• A gateway is used for splitting and joining flows
  • Gateways are typically used for if-then-else decisions

Data/Information

• Data can be either processed within a process or exchanged between different processes
• These data exchanges comprise five BPMN elements:
  • Data object
  • Data input
  • Data output
  • Data store
  • Message

Connecting Objects

• Allows an individual to connect flow objects to one another or to connect to supplementary information
• There are three different types of connecting objects:
  • Sequence flow
    • Sequence flows define the sequence of activities performed in a process
  • Message flow
    • Message flows show the flows of messages between two participants
    • A message flow connects two separate pools or objects within separate pools, but never within the same pool
  • Association
    • Associations associate data, text, and other artifacts with flow objects

Swim Lanes

• Used to group the primary modeling elements
• There are two types of groupings in BPMN: pools and (swim) lanes
  • Pool is used to represent a participant in a process; it can partition a set of activities from others
  • Lane is used for sub-partitions within a pool, and can divide activities

Artifacts

• Provide additional information about a process
• There are two types of artifacts: group and text annotation

Events

• The most common types of events are start and end events, which are used in top-level processes
• Start events depend on how such events are triggered
  • Most common way of marking the beginning of a BPMN process is with a message trigger

Event Triggers

• Here is a list of various types of triggers:
  • Message trigger
  • Timer trigger
  • Condition trigger
  • Signal trigger (similar to a message trigger)
  • Multiple and parallel multiple triggers

End Events

• End events represent the different results a process may produce
• Typically, the type of end event is the logical counterpart of the corresponding type of start event

Event Results

• Here is a list of various types of results:
  • Message result
  • Signal result
  • Multiple results

Activities

• A process is comprised of several subprocesses and activities
• BPMN 2.0 defines several kinds of activities:
  • Service task
  • Send task
  • Receive task
  • Instantiating receive task
  • Manual task
  • User task
  • Script task
  • Business rule task

Subprocesses

• An activity can be defined as a subprocess meaning insertion into that point can occur
• Subprocesses are of two forms:
  • Collapsed: looks like a regular activity except for the plus sign indicating it contains additional process logic
  • Expanded: shows the logic contained inside, follows the same design principles as a top-level process

Gateways

• Used to represent decisions, with different types of gateways available
• Each gateway that splits the flow in multiple paths is matched by another gateway of the same type that merges those paths
• BPMN 2.0 defines several kinds of gateways: exclusive, parallel, inclusive, complex

Looping

• A process represents a sequence of activities with each activity executed before moving to the next
• Activities are typically executed at most once, but can be run multiple times in practice
• BPMN allows the specification of whether an activity is to be executed multiple times
• Loop activity helps keep an activity running until a certain condition is true

Intermediate Events

• Intermediate events occur somewhere along the flow of the process
• In BPMN, an intermediate event that waits for some input is said to be "catching"

Intermediate Processes

• Here is a list of intermediate processes:
  • Timer event waits until a deadline is reached or a certain amount of time, has passed
  • Condition event waits until a certain condition is true
  • Signal event waits for a certain signal
  • Multiple event can wait for multiple things to happen

Event-Based Gateway

• Event-based gateways are similar to intermediate events with multiple triggers
• The first event to occur will determine the branch to be followed and the remaining branches will be skipped

Exception Handling

• In BPMN, there are ways to represent exceptions and include behavior specifically targeted at handling them
• The BPMN 2.0 language provides several constructs to represent exception handling
  • Error events
  • Intermediate events
  • Escalation events
  • Event subprocesses

Error Events

• These are the traditional solution to the problem of representing exceptions in BPMN
• The error event is a special kind of event that can take the form of an intermediate event if the error is being caught
• The error event can take the form of an end event if the error is being thrown

Intermediate Events

• These are attached to the boundary of activities and are the most commonly used constructs to represent exceptions
• The attached events are interrupting events, meaning their occurence interrupts the execution of the activity
• BPMN enables noninterrupting attached events where an inquiry can be handled with a response returned without interrupting the activity

Escalation Events

• These events are a variation on error events where the main purpose is to alert someone higher up in the business
• Escalation events mean that someone with higher responsibility (e.g. supervisor) will be called to intervene or at least be notified
• A difference between error events and escalation events is escalation events may be thrown by intermediate events
• Another difference is that escalation events may be caught by noninterrupting attached events

Event Subprocesses

• Event subprocesses can be triggered by an event occuring in parallel with the main process flow
• This event may occur at any point during the process, and the subprocess will be run immediately as a reaction to that event
• An event subprocess is able to keep listening for events during the entire duration of a process

Transactions

• Transactions in business processes work differently from traditional database systems' transactions
• In business processes, there are long-running transactions with the work committed in a stepwise function
• BPMN languages provide constructs to represent transactions and compensation in business processes:
  • Compensation handlers: Association between task A and task B means task B is the compensation handler for task A
  • Transactional subprocesses: Transactional subprocesses act as a container serving other activities/subprocesses
  • Compensation events: Compensation handlers can also be triggered through compensation events

Summary of BPMN

• BPMN is a graphical notation for modeling business processes
• Provides a range of elements to create business process models
• Notation of BPMN is sufficiently clear and describes process behavior to be translated into an executable form