Project Activity Diagram

A project will consist of number of tasks to be performed. These tasks need to be performed by taking into account all interactivity dependencies. Some of the tasks have to be performed in pure sequence while many tasks can be done concurrently. 

The team will examine the list of tasks and will decide the dependencies between them to come up with an order of sequence in which they will be carried out. Every task will have a predecessor and also a successor. Creating a right sequence of tasks will ensure that the tasks are done properly and the final deliverables come out nicely. Optimum sequence will also ensure that we can complete all the tasks in the most optimum time by leveraging concurrency.

There are 2 different methods for creating an activity sequence diagram as below:

• Precedence Diagramming Method (PDM) – This is also known as Activity on Node (AON)
• Arrow Diagramming Method (ADM – This is also known as Activity on Arrow (AOA)

Precedence Diagramming Method is popular and used most frequently. Arrow Diagramming Method has limitations and is not easy to understand; hence ADM is not used so often.

Precedence Diagramming Method allows use of 4 different type dependency relationships such as Finish-to-Start (FS), Start-to-Start (SS), Finish-to-Finish (FF) and Start-to-Finish (SF) to create an optimum activity sequence diagram. This provides immense flexibility. 

Arrow Diagramming Method only allows the use of Finish-to-Start (FS) relationship, leading lot of limitations. ADM also uses dummy activities to preserve the correct dependencies.