INFOSYS 220 Chap.5 Activity Diagrams and Process Analysis
Activity Diagrams and Process Analysis
Make behaviour and conditions visible
An activity diagram models procedural flow through actions, transitions, decisions and parallel work. The course rule uses one initial state and permits multiple final states. A decision sends one incoming route through guarded alternatives; a merge reunites alternatives. A fork begins concurrent routes and a join synchronises them.
The diagram can expand a use case or represent a broader business process, but every route needs a meaningful ending.
Choose a model for the question
Process analysis compares current and future work, searching for delay, bottlenecks, poor handoffs, unnecessary activity and automation opportunities. A data flow diagram answers a different question: how data enters, is transformed, is stored and leaves.
Every data flow connects to a process; each process needs input and output; parent and child levels must balance. Neither model replaces stakeholder walkthroughs or evidence about actual work.
What this chapter covers
- 01
Actions, transitions, initial and final states
- 02
Decision guards, merges, forks and joins
- 03
Normal, alternative and exception routes from use case documents
- 04
Current and future process analysis
- 05
External entities, processes, stores and flows in a data flow diagram
- 06
Decomposition, balancing, syntax and semantic checks
Worked example · free
Correct a service approval flow
- 2Apply the single start rule.
- 3Add guards and correct the outcomes.
- 1Explain fork or join misuse.
- 2Distinguish the data flow view.
Key terms
- Activity Diagram
- A UML behaviour model showing actions, conditions, routes and parallel work.
- Guard
- A condition attached to an outgoing route that determines when that route may be followed.
- Fork
- A synchronisation bar that splits one route into concurrent activity paths.
- Join
- A synchronisation bar that waits for required concurrent paths before work continues.
- Process Analysis
- Study of current or future work to assess effectiveness, efficiency, gaps and change impact.
- Data Flow Diagram
- A logical model of processes, external entities, data stores and named data movements.
- Balancing
- Preserving the parent process inputs and outputs when it is decomposed into a lower level diagram.
Activity Diagrams and Process Analysis FAQ
Can an activity diagram have several starts?
The course direction is exactly one initial state. Several final states are allowed when routes end differently. A diagram with multiple starts loses a single entry point and makes it unclear how the represented activity begins.
When is a join required?
A join is used when concurrent paths created by a fork must synchronise before the next action. It should not reunite mutually exclusive decision outcomes, because only one alternative route occurs and the join would wait for a route that never began.
How does a data flow diagram differ from an activity diagram?
An activity diagram emphasises behavioural order, decisions and parallel routes. A data flow diagram emphasises data transformation, storage, external sources or destinations and named flows. It does not represent program control logic or the detailed chronology of user actions.
What does balancing test?
Balancing checks that decomposition preserves the external inputs and outputs of the parent process. Lower level processes explain how the transformation occurs, but they should not silently invent or lose boundary flows. Consistent terminology also helps reveal mismatch across levels.
Exam move
Use one documented use case as the source for both models. Highlight normal and alternative steps in one colour and exceptions in another. Draw one initial state, convert verbs into action nodes, place guards on decisions and end every route. Add a fork only if two activities genuinely proceed concurrently, and add the matching join only if later work depends on both.
Read each route aloud as a scenario and compare it with the use case document. Next, redraw the same situation as a data flow diagram. Identify external entities, transformations, stores and named data, then apply the rule that every flow starts or ends at a process. Check that each process has an input and an output. Decompose one process and compare the child boundary flows with the parent.
This side by side exercise prevents symbols from drifting across model types. For process analysis, mark waiting, rework, handoffs and repeated data entry on the current state before proposing automation. Write one improvement that changes time, one that changes a role boundary and one that removes an unnecessary activity.
Finish by testing readability at report size and conducting a walkthrough from the perspective of a stakeholder who did not draw the model.
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