Activity diagrams describe the actual workflow behavior of an information technology system. These diagrams are very similar to state diagrams because activities are the actual state of doing something. These diagrams describe the real status of the activities of a system showing the entire sequence of activities carried out. Also, these diagrams can show conditional or parallel activities.
When to use it: activity diagrams
Activity diagrams should be used in conjunction with other modeling techniques such as interaction diagrams and state diagrams. The main reason behind using these diagrams is to model the workflow behind the system being designed. These diagrams are also useful for analyzing a use case by describing what actions should take place and when they should occur, describing a complicated sequential algorithm, and modeling applications with parallel processes.
Advantages of activity diagrams:
- The UML modeling language included that these diagrams are typically easily understandable to both analysts and stakeholders.
- In UML for the IT business analyst, “The activity diagram is most useful for the IT BA to represent the workflow [because] it’s easy to understand, both for BAs and end users. “
- Since they are among the easiest to use diagrams available, they are generally considered an essential tool in an analyst’s repertoire.
- Additionally, as noted above, activity diagrams allow an analyst to display multiple conditions and actors within a workflow through the use of lanes. Lanes, however, are optional since a single condition or actor is normally displayed without them.
Disadvantages of activity diagrams:
The UML modeling language includes that these diagrams have the potential to become overly complex because their easy-to-use nature can lend themselves to a complete description. In other words, since the project-related information is so easy to display, why not include it in its entirety? When an analyst has a large project, creating an overly complex single diagram can be a temptation.
However, as one author points out, “if you are using activity diagrams to define the structure of a workflow, you should not attempt to explore various levels of activity graphs down to their most ‘atomic’ level.” Instead, an analyst should try to present a new diagram for each workflow or, if more applicable, use lanes to present different actors within the same workflow.
Another aspect of these diagrams is that they cannot be used in place of a state diagram or sequence diagram because “the activity diagrams do not give details about how the objects behave or how the objects collaborate.” This is not a disadvantage in itself, but it is important for an analyst to keep it in mind when applying diagrams to their work.
In conclusion, activity diagrams are fairly easy to learn and will be useful for most projects because they clearly and moderately demonstrate how things work. ”Unlike many diagramming techniques, these diagrams also allow the representation of multiple options and actors within a workflow, and are easy to follow even for non-technical users
Activity diagram applications:
This diagram has been expanded to specify the flows between steps that transmit physical matter (eg, gasoline) or energy (eg, torque, pressure).
- Additional changes allow the diagram to better support continuous behaviors and continuous data flows.
- The UML 2 specification significantly extended the characteristics and scale of activity diagrams beyond their previous classification as a special case of state diagrams.
- Today, activity diagrams can be thought of as flowcharts for the 21st century, and UML modelers use activity diagrams to describe them.
- Also, these diagrams are useful in the following methods:
- Business rules
- Functions that occur in parallel
- Complex chain of multiple use cases
- Software flows and logic control configurations
- Procedures with judgment points and alternate flows
- Single use cases