Understanding Constraints in Primavera P6
Constraints are applied to Activities when relationships do not provide the required result and are often a result of External Dependencies.
Typical applications of a constraint are to constrain an activity to a date for:
- The availability of a site to commence work.
- The supply of information by a client.
- The required finish date of a project.
Constraints are often entered against Milestone activities to represent contract dates and may be directly related to contract items using Notebook Topics.
Constraints are covered in detail in the Constraints chapter.
There are four types of dependencies available in Primavera P6:
- Finish-to-Start (FS) (also known as conventional)
- Start-to-Start (SS)
- Start-to-Finish (SF)
- Finish-to-Finish (FF)
Two other terms you must understand are:
- Predecessor, an activity that controls the start or finish of another immediate subsequent activity.
- Successor, an activity where the start or finish depends on the start or finish of another immediately preceding activity.
The following pictures show how the dependencies appear graphically in the Bar Chart and Activity Network (also known as PERT, Network Diagram and Relationship Diagram Views):
The FS (or conventional) dependency looks like this: