dependencies in project management

4 Types of Dependencies In Project Management With Examples

You might know there are 4 types of dependencies in project management viz. Mandatory, Discretionary, External, & Internal.

In this article, you will find definitions, detailed description, and examples of different types of schedule dependencies. It follows from my previous article where I explained basics of dependencies.

Project Dependencies are better characterized as Schedule Dependencies. To understand the foundational concepts you should read my previous article.

4 Types Of Dependencies In Project Management

Mandatory Dependency

Mandatory Project Dependencies are are legally or contractually required. They are, sometimes, inherent in the nature of the work. They 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 Dependency

Discretionary Project Dependencies are defined by the Project Team. There could be more than one way to define a sequence between 2 activities. The Project Team may prefer one sequence over the other. The team would choose their preferred sequence because of best practices or lessons learned from prior experiences. These are also called Preferred Logic, Preferential Logic or Soft Logic.

Consider 2 activities A and B. A and B can be independently performed or one can be performed after the other. The Project Team can chose 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 Dependency

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 e.g. representatives from Client’s organization, Vendors’ organization 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. If B has an External Dependency on A then it would signify that 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 Dependency

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. If B has an Internal Dependency on A then it would signify that 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

Project Relationships Are Not Dependencies

You would have noticed that I have not talked about activity relationships in this article.

Activity relationships are closely related to project dependencies but have a different meaning. In some project management literature you will find the terms dependency and relationship used interchangeably. This is factually incorrect.

Like dependencies, there are 4 types of relationships – Finish to Start, Finish to Finish, Start to Start and Start to Finish.

All 4 dependencies can be expressed for all 4 relationships.

Final Words – Conjunction Of Project Dependencies

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

Over To You

How do you use dependencies in your projects? Do you document them in a separate log? Are they shared with different stakeholders?

Please share your thoughts and leave a comment below.

16 thoughts on “4 Types of Dependencies In Project Management With Examples”

  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.

  2. Hard logic the client’s approval is something where we the contract papers comes to action. I have seen most of the time a Client put a Consultant in between and it becomes harder to get approvals.


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