4 Types of Project Dependencies

4 Types of Project Dependencies

I wrote an article to describe what are Project Dependencies. Project Dependencies are better characterized as Schedule Dependencies. In this article, I will describe different types of Project Dependencies.

types of project dependencies

Types of Project Dependencies are characterized by 4 different attributes:

  • Mandatory
  • Discretionary
  • External
  • Internal

You should also read my other articles on 4 Types of Project RelationshipsFinish to Start, Finish to Finish, Start to Start and Start to Finish. All 4 Project Dependencies are applicable on all 4 Project Relationships.

Out of the 4 types of Project Dependencies, only 2 are applicable in a given Project Relationship. Let us first understand different types of Project Dependencies. I will explain the definitions of each type of dependency with the help of few examples.

Mandatory

Mandatory Project Dependencies are those that are legally or contractually required. They are, sometimes, inherent in the nature of the work. Mandatory Project Dependencies are also called Hard Logic.

Consider 2 activities A and B. If B has a Mandatory Dependency on A then it means action on B cannot be performed until Action on A has been completed. Let us look at following examples to understand:

  • A – Requirements Documentation; B – Client Approval
  • A – Lay Building Foundation; B – Construct Floor
  • A – Build Car Prototype; B – Perform Crash Testing

Discretionary

Discretionary Project Dependencies are defined by the Project Team. There could be more than one way to define the sequence between 2 activities. The Project Team, however, prefers one sequence over the other sequences. There could be different reasons for the proffered sequence of the Project Team like best practices or lessons learned from prior experiences. Discretionary Project Dependencies are also called Preferred Logic, Preferential Logic or Soft Logic.

Consider 2 activities A and B. If B has a Discretionary dependency on A then it means action on B can be performed even before Action on A has been completed. It can also mean that action on A and B can be independently performed. However, the Project Team has chosen to make B dependent on A. Let us look at following examples to understand:

  • A – Develop System Module X; B – Develop System Module Y
  • A – Furnish Room R; B – Furnish Room S
  • A – Book Airline Ticket; B – Buy Insurance

External

External Project Dependencies are defined between non-project Activities and project activities. The non-project activities are done by people who are external to the Project Team. It means people who are not part of the Project Team e.g. Client, Vendors or any other external groups. The project activities, on the other hand, are done by the Project Team. The Project Team usually does not have control over non-project activities.

Consider 2 activities A and B. B has an External Dependency on A. It means B is a project activity while A is a non-project activity. Following examples will be helpful in understanding:

  • A – Client Go-Ahead; B – Initiate Project
  • A – Delivery of Equipment; B – Start Development
  • A – Approval of Building Plans; B – Start Construction

Internal

Internal Project Dependencies are defined between two project activities. The Project Team, usually, has complete control over project activities.

Consider 2 activities A and B. B has an Internal Dependency on A. It means both A and B are project activities. These are performed by the Project Team members. There is no involvement of any external party. Let us look at following examples to understand:

  • A – Develop System; B – Test System
  • A – Construct Wall; B – Paint Wall
  • A – Assemble Machine; B -Pack Machine

Concluding Comments

There are a total of 4 Types of Project Dependencies. However, only 2 are applicable at the same time. Project Dependency between 2 activities could be any one of the following:

  • Mandatory-External
  • Discretionary-External
  • Mandatory-Internal
  • Discretionary-Internal

I have noticed that sometimes there is a confusion between a Project Dependency and a Project Relationship. Sometimes one is used in place of the other. These are two distinct terms and should be used appropriately. Please leave a comment if you want to add more to the topic or if you have a question.

Praveen Malik, PMP is a certified Project Management Professional (PMP®) with a rich 20+ years of experience. He is a leading Project Management Instructor and Consultant. He regularly conducts Project Management workshops in India & abroad.

6 thoughts on “4 Types of Project Dependencies

  1. Thanks for the clarity, I just stumbled on the different types of dependencies and wanted to know more about it then your site provided a very good explanation with examples to it, thanks and keep up the good work

    One more thing though, looking at the dependencies, it kind of sounds like the internal dependencies can also be mandatory dependencies, or what is your take on that.

    • Thanks Michael. Please look at the “Concluding Remarks” in the article. I have mentioned there 4 different combinations: Mandatory-Internal is one of them.

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