A Logical Relationship defines a dependency between two activities or between an activity and a milestone in a project schedule. It determines how tasks are sequenced and connected, influencing project flow and scheduling decisions.
Key Types of Logical Relationships
- Finish-to-Start (FS) – The successor task cannot begin until the predecessor task finishes.
- Finish-to-Finish (FF) – The successor task cannot finish until the predecessor task finishes.
- Start-to-Start (SS) – The successor task cannot start until the predecessor task starts.
- Start-to-Finish (SF) – The successor task cannot finish until the predecessor task starts.
Example Scenarios
Software Development
- FS Example: Testing cannot begin until coding is completed.
- SS Example: Frontend and backend development start simultaneously.
Construction Project
- FF Example: Electrical work must finish before final inspections can finish.
- SF Example: A shift handover cannot be completed until the next shift begins.
Event Planning
- FS Example: The event venue setup must be completed before guest registration starts.
- FF Example: Marketing efforts must continue until ticket sales conclude.
Mermaid Diagram: Logical Relationships in Scheduling
flowchart LR A[Task A Predecessor] -->|Finish-to-Start FS| B[Task B] A -->|Start-to-Start SS| C[Task C] B -->|Finish-to-Finish FF| D[Task D] C -->|Start-to-Finish SF| E[Task E]
Why Logical Relationships Matter
- Defines Task Dependencies – Ensures proper sequencing of activities.
- Prevents Scheduling Conflicts – Helps avoid misaligned tasks and delays.
- Optimizes Project Flow – Facilitates efficient execution of work packages.
- Supports Critical Path Analysis – Essential for determining key project constraints.
See also: Finish-to-Finish (FF), Finish-to-Start (FS), Start-to-Start (SS), Start-to-Finish (SF), Schedule Dependencies.