If a task is a non-parent task, it could have dependency tasks. The predecessor tasks determine the dates of the current task. The dates of the successor tasks are determined by the current task.
To define dependency relations, use the "Editing Task" window. To open the window, double-click a task name on the Gantt sheet.
There are four types of dependencies.
| Dependency | Chart | Usage |
|---|---|---|
| Finish to start |  | The predecessor task’s end date determines the successor task’s start date. |
| Start to start |  | The predecessor task’s start date determines the successor task’s start date. |
| Finish to finish |  | The predecessor task’s end date determines the successor task’s end date. |
| Start to finish |  | The predecessor task’s start date determines the successor task’s end date. |
A task could have multiple predecessors and successors. If multiple predecessors determine the start date of a task, the latest date is used; likewise, if multiple predecessors determine the end date of a task, the latest date is used.
There is only one dependency relation allowed between two tasks. For example, if there are two tasks A and B, it isn’t allowed to define two dependencies between the two tasks.
Also, cyclic dependency should be avoided. For example, if the start date of Task A is determined by Task B and the start date of Task B is determined by Task C, you cannot define say the start date of Task C is determined by Task A. The "Refresh All" button on the Excel ribbon can detect this type of dependency.
For each dependency relationship, you can specify a "Lag". The lag is the additional time between the two tasks. For example, if Task A has a "Finish to Start" relationship with Task B and Task A ends on August 1st and the lag is 2, then Task B starts on August 4th. The calculation of lag does not consider rest days and holidays defined by resources.