BPMN 2.0 Flow Objects

The flow objects are divided into the following three groups:

  • Activities
  • Gateways
  • Events

Activities

Belong to the group of activities:

  • Tasks
  • Transactions
  • Event Subprocess
  • Call Activity

Task

A task is an elementary unit of work.

An additional [+] marks an activity as a closed subprocess.

 

Annotation:
Most BPMN modeling tools allow a subprocess to be expanded or collapsed by clicking on the [+] symbol. As a result, any detailing of the representation (zooming) can be achieved, as a result of which the readability and comprehensibility of the diagrams is substantially improved.

Example:

Transaction

A transaction is a group of activities that logically belong together.

The transaction log can also be specified.

 

Event Subprocess

An event subprocess is placed in another sub-process. It is triggered by a start event and can interrupt the surrounding sub-process – depending on the type of start event – or interrupt it in parallel.

 

 

Call Activity

A Call Activity represents either another process or a globally defined task that is used (called) in the current process.

 

 

Gateways

Through the use of gateways, two goals are achieved in process sequences:

  • Branching of a process execution into alternative (split) or multiple (fork) execution paths, or
  • Merging of multiple alternative (merge) or concurrent (join) execution paths

Gateways can occur in different forms:

  • Default or Exclusive (XOR) Gateway
  • Parallel (AND) Gateway
  • Inclusive (OR) Gateway
  • Event-based Gateway
  • Complex Gateway

The different types of gateways differ in branch and merge behavior!

Exclusive (XOR) Gateway

Branching: The flow is directed to exactly one outgoing edge, depending on conditions.

Merging: It waits for (any)one of the incoming edges to activate the outgoing flow.

 

Parallel (AND) Gateway

Branching: All outgoing edges are activated simultaneously.

Merging: It waits for all incoming edges before the outgoing flow is activated (synchronization).

 

Inclusive (OR) Gateway

Depending on the condition, this gateway activates one or more outgoing edges or synchronizes incoming edges.

The logic of behavior is attached in the form of an annotation.

 

Event-based Gateway

This gateway is followed by events or recipient tasks.

The sequence flow is directed to the event that occurs first.

 

Exclusive (XOR) event-based Gateway

The process is started or continued if one of the following events occurs.

 

 

Parallel (AND) event-based Gateway

The process is started or continued when all of the subsequent events occur.

 

 

Complex Gateway

This gateway is for branch and merge scenarios that are not covered by the other gateways.

The logic of behavior is attached in the form of an annotation.

 

Events

Occurring events are distinguished as follows …

  • the position in the process: Start, Intermediate, End
  • the effect: Catching („white symbol“), Throwing („black symbol“)
  • the kind: Message, Timer, Exception, …

The first group (position in the process) is differentiated according to the type of surrounding circle.

 

 

 

The second group (effect) according to the color of the symbol inside the circle:

A white icon (catching) indicates that an event is being received,

a black symbol (throwing) indicates that an event is triggered.

 

 

 

 

The symbol inside the circle indicates the third distinction criterion (type).

 

 

 

Combining these characteristics results in several concrete event types.

Posts (Activities):

Posts (Gateways):

Posts (Events):

Additional Information: Participants • Connecting Objects • Artifacts

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