No person can survive in isolation. we are all interconnected and dependent on each other for the essentials of life. There is hardly anything in our world that has absolutely no connection with something else. The same goes with project management, a project is made up of several tasks or activities and every activity has some dependencies. No activity or task exists in isolation, they either affect other tasks or get affected by them.
If you are a project manager, this article is all you need to understand what project dependencies are, their types, and how they help in managing projects in a better way.
Precedence Diagramming Method in Project Management
Precedence diagram is a technique that helps the project team to schedule the project activities. It is used for constructing a schedule model where activities are represented by nodes and are graphically linked by one or more logical relationships to show the sequence in which the activities are to be performed.
So, what is Task Dependency?
After the resource allocation, the next big challenge for the project manager is to schedule a task. For that, the Project manager must need to identify dependencies between tasks.
In project management, dependency is a logical relationship between activities and tasks such that the initiation and completion of one activity are dependent on the initiation and completion of the other activity. In other words, one preceding activity relies on the other succeeding one.
Predecessor activity: An activity that logically comes before a dependent activity in a schedule.
Successor activity: An activity that logically comes after another activity in a schedule.
Lead and Lag in Project Management
Lead and Lag are two important scheduling terms used with relationships like Finish to Start, Start to Start dependencies. It may occur between multiple scheduled activities.
Lead Time in Project Management
According to the PMBOK Guide 6th Edition, “A lead is the amount of time whereby a successor activity can be advanced with respect to a predecessor activity.”
In simple words, lead allows successor activity to start early. For Example, let assume that the time duration for the designing activity is 10 days and the time duration for the coding activity is 20 days. The designing activity is on its 5th day and you have started the coding activity. While there are still 5 days for the designing activity, the coding activity has started 5 days in advance before the design activity finishes. Here, the lead time will be of 5 days. The Project manager usually uses this technique to reduce the overall time of the project.
Lag Time in Project Management
According to the PMBOK Guide, 6th edition, “A lag is the amount of time a successor activity will be delayed with respect to a predecessor activity.”
It is opposite to lead, lag makes successor activity to delay its start. For example, let assume that the duration of the developing activity is 20 days and the duration of the testing activity is 5 days. After completing the developing activity, you wait for 2 days, and then you start the testing activity. Here, the delay of 2 days is lag time.
Types of dependencies in project management
There are four types of dependencies or logical relationships in the Precedence diagramming method.
- Finish-to-start (FS): A logical relationship in which a successor activity cannot start until a predecessor activity has finished. For Example, activity A should be completed in order to give start to activity B.
- Finish-to-finish (FF): A logical relationship in which a successor activity cannot finish until a predecessor activity has finished. For Example, activity A should be completed before activity B will be completed.
- Start-to-start (SS): A logical relationship in which a successor activity cannot start until a predecessor activity has started. For Example, activity B can only start when activity A has started.
- Start-to-finish (SF): A logical relationship in which a successor activity cannot finish until a predecessor activity has started. For Example, activity B can only finish when activity A has started.
Gantt Chart Representation:
|||P. M. Institute, A Guide to the PROJECT MANAGEMENT BODY OF KNOWLEDGE, Newtown Square, Pennsylvania, USA: Project Management Institute, Inc, 2017.|