There are several types of dependency relationships that you can apply between two tasks. The first task in the relationship is known as the predecessor and the second called the successor. Dependency types and descriptions are provided here:
The successor project task cannot finish until the predecessor project task is complete.
No
When a dependency is created between two tasks, the successor task's details are recalculated according to the dependency type you apply. The recalculation is also influenced by which duration unit each task is set to. The predecessor task does not move unless you manually change its details. When there are more than two tasks in a dependency, the predecessor task's details are recalculated appropriately when it is also a successor to another predecessor task.
These examples show the recalculation of the successor task when both tasks are in the duration unit of hours.
Predecessor
Successor
Dependency Type Applied
Recalculated Successor
Mon 01/01
7am - 2pm
Mon 01/01
11am - 3pm
Start to Start
Mon 01/01
7am - 11am
Mon 01/01
11am - 3pm
Mon 01/01
7am - 2pm
Start to Start
Mon 01/01
11am - 6pm
Mon 01/01
11am - 3pm
Mon 01/01
9am - 5pm
Finish to Finish
Mon 01/01
7am - 3pm
Mon 01/01
11am - 3pm
Mon 01/01
7am - 2pm
Finish to Finish
Mon 01/01
8am - 3pm
Mon 01/01
7am - 2pm
Mon 01/01
4pm - 10pm
Finish to Start
Mon 01/01
2pm - 8pm
Mon 01/01
7am - 2pm
Mon 01/01
11am - 3pm
Finish to Start
Mon 01/01
2pm - 6pm
Mon 01/01
7am - 2pm
Mon 01/01
11am - 3pm
Start to Finish
Mon 01/01
3am - 7am
Mon 01/01
7pm - 2am
Mon 01/01
11am - 3pm
Start to Finish
Mon 01/01
3pm - 7pm
About Lag Time on Task Dependency Relationships
Lag can be applied when there is a dependency relationship between two project tasks. The lag is the time gap added or subtracted from the end of a predecessor task before the successor task can start. The default lag is 0. Lag time can be a positive or negative value. For more information, see the description for the Lag field.
Formulas recalculate project task start or end dates and times accordingly in dependencies when you update the dependency's lag time.
Dependency Type
Recalculation
Lag Formula Used
Finish to Start
Start of the successor task.
Finish of the predecessor task plus or minus any applied lag time.
Start to Finish
Finish of the successor task.
Start of the predecessor task plus or minus any applied lag time.
Start to Start
Start of the successor task.
Start of the predecessor task plus or minus any applied lag time.
Finish to Finish
Finish of the successor task.
Finish of the predecessor task plus or minus any applied lag time.