A Dependency is a logical relationship between two or more activities, where the timing, sequencing, or completion of one activity depends on another. Dependencies define the order of execution in a project schedule and impact overall project flow.
Key Aspects of Dependencies
- Control Task Sequencing – Dictate the order in which tasks must be performed.
- Impact Schedule Management – Delays in dependent tasks can affect project deadlines.
- Can Be Mandatory or Discretionary – Some dependencies are fixed, while others are based on best practices.
- Essential for Critical Path Analysis – Help determine the longest project duration.
Types of Dependencies
Type | Description | Example |
---|---|---|
Finish-to-Start (FS) | Task B cannot start until Task A is finished. | A house cannot be painted until construction is completed. |
Start-to-Start (SS) | Task B can start only after Task A has started. | Coding and testing can begin simultaneously after requirements are finalized. |
Finish-to-Finish (FF) | Task B cannot finish until Task A is finished. | Final editing of a book cannot be completed until writing is finished. |
Start-to-Finish (SF) | Task B cannot finish until Task A has started. | A security shift cannot end until the next shift has started. |
Mermaid Diagram: Dependency Example
graph LR; A["Task A: Lay Foundation"] -->|FS| B["Task B: Build Walls"] B -->|FS| C["Task C: Install Roof"] C -->|FS| D["Task D: Paint Exterior"] B -->|SS| E["Task E: Start Interior Work"] D -->|FF| F["Task F: Final Inspection"]
Example Scenarios
Software Development
A code review (Task B) cannot begin until code implementation (Task A) is completed (Finish-to-Start dependency).
Construction Project
Plumbing installation (Task B) must start at the same time as electrical wiring (Task A) (Start-to-Start dependency).
Event Planning
A marketing campaign launch (Task B) cannot be completed until advertising content creation (Task A) is finalized (Finish-to-Finish dependency).
Why Dependencies Matter
- Ensure Logical Task Sequencing – Define relationships between project activities.
- Improve Scheduling Accuracy – Helps in setting realistic deadlines.
- Identify Bottlenecks Early – Allows proactive risk mitigation.
- Support Critical Path Analysis – Helps determine key project constraints.
See also: Critical Path Method (CPM), Task Sequencing, Project Schedule, Lead and Lag Time.