In any project, tasks often rely on one another either sequentially or concurrently. Dependencies establish the order in which tasks should be executed to ensure smooth progress towards project completion. Understanding and managing these dependencies are crucial for effective project planning and execution.

This article will explain the different types of task dependencies that can be utilised on the project schedule, how to create these dependencies, reviewing the linked dependencies, and how to update the dependencies using the replan function.

Understanding Task Dependencies

Task dependencies are relationships that define the order in which tasks need to be performed. Recognising these relationships is essential for efficient project planning, execution, and control. By effectively managing dependencies, project teams can enhance productivity, mitigate risks, and ensure timely project completion.

Fluid supports four types of task dependency relationships: Finish-to-Start, Start-to-Start, Finish-to-Finish, and Start-to-Finish. Each type has a specific role in defining how tasks relate to one another.

Dependency Type	Description	Dependency link on the UI
Finish-to-Start	Description: The predecessor task must finish before the successor task can start. Example: Land must be bought before building can begin. UI Representation: A line connects the end point of the predecessor to the start point of the successor.
Start-to-Start	Description: The predecessor task must start before the successor task can start. Example: Excavation must start before foundations can be laid. UI Representation: A line connects the start point of the predecessor to the start point of the successor.
Finish-to-Finish	Description: The predecessor task must finish before the successor task can finish. Example: Plastering must be completed before painting can be completed. UI Representation: A line connects the end point of the predecessor to the end point of the successor.
Start-to-Finish	Description: The predecessor task must start before the successor task can finish. Example: Roof installation must start before interior painting can be completed. UI Representation: A line connects the start point of the predecessor to the end point of the successor.

Lag Time

Each dependency has a lag time, which is the delay between the predecessor and the successor. Lag time is set to 0 by default when a dependency is created. However, this can be adjusted to account for necessary delays or overlaps between tasks.

• Positive Lag: Adds delay between the end of the predecessor task and the start of the successor task. For example, if there's a 2-day lag, the successor task will start 2 days after the predecessor task ends.
  
  
• Negative Lag (Lead Time): Allows the successor task to start before the predecessor task finishes. For example, if there's a -2 day lag, the successor task will start 2 days before the predecessor task ends.
  
  

Adjusting the lag time helps in managing the flow of tasks and ensures that the project timeline accurately reflects the necessary delays or overlaps between tasks.

Creating Task Dependencies

To create dependencies between tasks on the Gantt chart, follow these steps:

1. Identify Task Points: Each task has start and finish points (dots at the beginning and end of the task) visible when hovering over the task on the Gantt chart.
   
   
2. Drag and Link: Click and drag the start or finish point of one task to the start or finish point of another task. This action creates a dependency link.
   
   
3. Set the lag time: Double-click on the link to set the lag time.

Example: The task "Design the electrical transmission system" has its end point linked to the start point of the task "Finalise the system architecture design." This link establishes a Finish-to-Start relationship.

Reviewing Task Dependencies

You can review task dependency relationships via the schedule task dialog or directly on the Gantt chart.

Via Task Dialog:

1. Open Task Dialog: Double-click on the task to open its dialog.
2. Navigate to Predecessors Section: View the list of predecessors and their details, including:
   • Title of Successor: Name of the task the predecessor is linked to.
   • Type: Type of dependency relationship.
   • Lag: Duration of the delay between the predecessor and successor.
   • Unlink: Option to delete the dependency.

Via Gantt Chart:

• Double-click on the Link: This action opens a minimised dialog showing the same link information as in the task dialog.