You can’t bake a cake unless you have all the ingredients, you can’t turn the TV on unless you’ve plugged it into a power socket, you can’t answer a question unless you’ve been asked one. These are all examples of situations where a task cannot start or finish before the one prior starts or finishes. This is also known as a dependency, or as the Max Wideman Glossary defines it, the ‘relationships between products or tasks’ such that ‘one requires input from the other’.
Thinking about dependencies in a project management context, it is clear to see that a project will never consist of a set of isolated tasks and that there will always be some sort of dependency. Hence, it is safe to say: Where there’s a project, expect a dependency.
What types of dependencies are there?
The type of dependency depends on the circumstances, relationships and other factors that condition it. These are the 5 most common examples of dependencies in project management:
- Logical Dependency (or Casual Dependency)
This happens where there is a fundamental task that needs to be completed in order for the next task to even initiate. It’s an inherent part of the project and cannot be avoided.
An example of this is creating a movie; the script and story board need to be planned before you can start to film.
- Discretionary Dependency (or Preferential Dependency)
This happens where there are several paths the project can take, but because of best practice, protocols or desired processes, there is a preferred sequence of tasks which includes certain dependencies.
An example of this is how someone makes a cup of tea. There are several different ways you can make a cup of tea; the main steps being to add a teabag, boiling water, milk and/or sugar to a mug… Whatever sequence of steps you choose to follow leaves you with the same result; a cup of tea.
- Resource-based Dependency
This depends on the resources available in the project. There is a dependency when two tasks require the same resources and there isn’t enough resource to do the tasks at the same time, making one task dependent on the other. There is no resource-based dependency where there is enough resource for all tasks.
An example of this is where two tasks in the project require all members of staff. In a case like this, one task must be completed before the next task can start, because of the lack of people.
- Internal Dependency (or Cross-team Dependency)
An internal dependency arises where there are multiple teams working in parallel to achieve the objective of a complex project. This is a very common dependency in large companies where there are multiple departments.
This dependency can arise where one team’s work feeds into another team’s work. For example, training staff members is dependent on having training material. If the creators of training material have not started or finished creating the materials, the team cannot start training.
- External Dependency
An external dependency is a task that the project manager does not have control over, its start or finish depends on a third party or external factor. Examples of external dependencies may be weather conditions affecting your harvest or waiting for a license or permission from a third party to continue your sequence of tasks.
What type of tasks are there?
Tasks themselves can create dependencies depending on their relationship with other tasks or what phase of the project they are in.
There are 4 types of task dependencies:
Look out for dependencies
A dependency in Project Management can pose a challenge to the timeline of a project by affecting a project manager’s scheduling and maintenance of the order and requirements of tasks. To successfully manage dependencies a project manager can:
- Identify possible dependencies by laying out the sequence of tasks in a project plan.
- Engage with stakeholders
- Make a risk log and keep updating it
- Make a contingency plan
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Resources:
- http://www.maxwideman.com/pmglossary/PMG_D02.htm
- https://rindle.com/blog/the-ultimate-guide-to-project-dependencies
- https://kissflow.com/project/dependencies-in-project-management/
