A Predecessor Activity is an activity that logically comes before a dependent (successor) activity in a project schedule. The timing and sequence of the successor are determined by the relationship with its predecessor.
Predecessor activities define how and when dependent work can begin or end, and are critical to building a schedule model using the Precedence Diagramming Method (PDM).
Key Characteristics
- Defines Sequence – Determines the order of activities
- Drives Dependency Logic – May influence start or finish of successors
- Used in All Schedule Models – Common to all network-based scheduling techniques
- Impacts Critical Path – Delays in predecessors can propagate downstream
Example Scenarios
- Code development must finish before testing can start (Finish-to-Start)
- Procurement must start before onboarding a vendor (Start-to-Start)
- Approval must finish before product launch can finish (Finish-to-Finish)
Mermaid Diagram: Predecessor Relationships
flowchart LR A[Predecessor: Design Complete] -->|FS| B[Successor: Development Begins] A -->|SS| C[Successor: Test Environment Setup] A -->|FF| D[Successor: Documentation Review Ends]
Why Predecessor Activity Matters
- Ensures Logical Flow – Creates a structured and traceable schedule
- Enables Accurate Forecasting – Allows impact analysis for upstream changes
- Supports Dependency Management – Identifies which tasks must be completed first
- Feeds Critical Path Analysis – Helps determine project timeline constraints
See also: Successor Activity, Summary Activity, Precedence Diagramming Method, Logical Relationship, Schedule Network Diagram.