Precedence Diagramming Method (PDM)

The Precedence Diagramming Method (PDM) is a network scheduling technique that visually represents project activities and their dependencies. It is commonly used in Critical Path Method (CPM) scheduling to define the sequence of work.

Key Aspects of Precedence Diagramming Method (PDM)

• Uses Nodes for Activities – Tasks are represented as boxes (nodes).
• Defines Task Dependencies – Uses arrows to show relationships between tasks.
• Supports Critical Path Analysis – Helps determine the longest sequence of tasks.
• Identifies Four Dependency Types – Finish-to-Start (FS), Start-to-Start (SS), Finish-to-Finish (FF), and Start-to-Finish (SF).

Types of Dependencies in PDM

1. Finish-to-Start (FS) – Task B cannot start until Task A finishes. (Most common)
2. Start-to-Start (SS) – Task B cannot start until Task A starts.
3. Finish-to-Finish (FF) – Task B cannot finish until Task A finishes.
4. Start-to-Finish (SF) – Task B cannot finish until Task A starts (Rarely used).

Example Scenario

Software Development Project

A simplified PDM example for feature release:

• Define Requirements (A)
• Develop Features (B)
• Perform Testing (C)
• Deploy to Production (D)

Mermaid Diagram: Precedence Diagramming Method Example

flowchart LR
    A[Activity A: Design] -->|FS| B[Activity B: Build]
    A -->|SS| C[Activity C: Prototype]
    B -->|FF| D[Activity D: Integration Test]
    C -->|SF| E[Activity E: Monitor Setup]

Why PDM Matters

• Optimizes Scheduling – Clearly defines how tasks are linked.
• Identifies Critical Path – Highlights activities that determine project duration.
• Prevents Scheduling Conflicts – Ensures tasks are sequenced correctly.
• Improves Resource Allocation – Helps teams plan workloads efficiently.

See also: Schedule Network Diagram, Critical Path Method (CPM), Dependency Management, Gantt Chart.