Step-1: Activity Diagram:
- A flowchart that visually represents the sequence of activities and decisions in a process or project. It shows the flow from one activity to another but lacks time or resource detail.
- Used primarily in UML (Unified Modeling Language) for software modeling.
Step-2: Network Diagram:
- A graphical representation of a project’s activities and their dependencies. It shows the order and sequence of tasks using nodes (activities) and arrows (dependencies).
- Two types:
- AOA (Activity on Arrow) – Arrows represent activities.
- AON (Activity on Node) – Nodes represent activities (most common).
Step-3: Forward Pass:
- Calculates the earliest start (ES) and earliest finish (EF) times for each activity, beginning at the project start.
- Formula:
Step-4: Backward Pass:
- Determines the latest start (LS) and latest finish (LF) times by moving backward from the project’s end.
- Formula:
Differences Between Activity Diagrams, Network Diagrams, and Gantt Charts
| Aspect | Activity Diagram | Network Diagram | Gantt Chart |
|---|---|---|---|
| Purpose | Models workflows/processes | Maps activity dependencies | Tracks task schedules over time |
| Visualization | Flowchart of activities | Nodes (tasks) and arrows (dependencies) | Bars showing task duration and overlap |
| Time Representation | No time element | Shows project timeline and dependencies | Directly shows duration, progress, and deadlines |
| Focus | Workflow, software modeling | Critical path and task dependencies | Schedule tracking and resource allocation |
| Use Case | Software and system modeling | Project planning and scheduling | Project management and tracking progress |
Step-5: Calculating the Critical Path
- Critical Path:
- The longest path through the network diagram. It shows the sequence of tasks that determine the shortest project duration. Any delay in the critical path delays the project.
Steps to Calculate Critical Path:
- List all project activities and durations.
- Identify dependencies (predecessors).
- Draw the network diagram.
- Perform forward and backward passes.
- Calculate slack for each activity.
- The path with zero slack is the critical path.
Step-6: Calculating Slack (Float)
- Slack:
- The amount of time an activity can be delayed without delaying the project.
- Formula:
- Zero Slack indicates the activity is on the critical path.
