Much like a relay race, projects are often completed by passing tasks from one team member to the next. Unlike a relay race, some project tasks require other tasks to move forward before they can be started. This relationship between tasks is known as a dependency.

As a project manager, understanding how dependencies work can help you define a clear and consistent plan before initiating the project itself. Here’s what you need to know.

What is a dependency in project management?

In general, a dependency is something that relies on something else.

General examples of a dependency:

• • Babies are dependent on caregivers
  • Plants are dependent on sunlight
  • Fish are dependent on water

As it relates to project management, a dependency is a task that relies on the completion of a different task.

Examples of dependencies in project management:

• • A company’s PR statement is dependent on the CEO’s approval of the messaging
  • A reimbursement is dependent on an expense report submission
  • A bug fix is dependent on the identification of its root cause

As a project manager, it’s important to keep tabs on all of your project dependencies so stakeholders are aware of when they need to begin their part of the project.

What are dependencies in Project Management

Types of dependencies in project management

While the concept of dependences is simple, they can come in many variations.

Logical dependencies

Also known as a causal dependency, these dependencies are parts of a project that are necessary for a project’s completion. They’re often the goal output for all of the preceding tasks and cannot run parallel with other tasks.

For example, you cannot delegate a task to someone else if you don’t have another person on your team. In this case, hiring another team member is considered a logical dependency.

Resource dependencies

Resource dependencies are project restraints as it relates to a limited amount of resources that you have for your project. If there are additional resources available for the project, this dependency would not be an issue.

For example, the progress of Project B is dependent on a single designer finishing Project A so that they have the bandwidth to complete Project B without getting overworked.

Read: Your guide to getting started with resource management

Preferential dependencies

Preferential dependencies are created by team-imposed processes, but are not necessarily required for a project to be completed.

For example, an editor may require one final review before sending an article to publish. While this is a step that’s created by the team to ensure there are no mistakes, this step isn’t necessarily needed for the project to be completed.

​​External dependencies

External dependencies are tasks that are dependent on outside factors that you or your team have no control over. Internal dependencies are more common, as they rely on things that your team can control.

A good example of an external dependency is when a weather phenomenon prevents a shipment of fresh fruit from arriving at a restaurant. A chef could have had a menu that required oranges, but due to a surprise frost, they’re unable to create the dishes necessary. The chef was externally dependent on the orange vendor for creating specific dishes.

Types of task dependencies in project management

Some dependencies are specific to the two tasks involved. Here are the most common types of task dependencies:

• Finish to Start (FtS): This is the most common task dependency. Task B cannot start until Task A is complete. This functionality is common in the Waterfall project management methodology.
• Finish to Finish (FtF): Task B cannot finish until Task A is also completed. This is common with tasks that have subtasks within them; if the subtasks are not completed, you cannot complete the parent task.
• Start to Start (StS): Task B cannot start before Task A starts. These are for tasks that are required to run in parallel with each other. A good example of this is a timed e-commerce launch. A social media marketer may want to post an announcement for a sale going live, right as a web developer pushes the correct web page to go live. The social media marketer does not start until the web developer starts to ensure that the announcement goes out at the same time.
• Start to Finish (StF): Task B must start for Task A to be completed. This is important for situations that require overlap. An example of this would be coverage on a support line. A representative cannot leave until a different representative comes to relieve them of their duties so that there is always someone available to provide customer support.

Attributions:

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