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What Is the Difference Between WBS, Project Plan and Project Schedule?

If you are new to the project world, you are confronted with lots of seemingly similar terms and definitions.

What is, for instance, the difference between a work breakdown structure, a project plan and a project schedule? Let's resolve the confusion.

I'm sorry to disappoint any expectations of a short answer: Although the three terms are sometimes used interchangeably, they are no synonyms but usually relate to very different management tools.

Why usually?

There is no uniform definition of neither of the three terms. Depending on the project management methodology you follow, different meanings may be associated. It may very well happen that in one context a project plan is defined in a particular way and in another context it means something different. With this warning ahead, the distinction presented in this article will apply to most circumstances.

Work breakdown structure (WBS)

The work breakdown structure (WBS) is at the core of project planning. Project managers use the WBS to divide the project into controllable elements. It is a visual and hierarchic representation of all work needed to complete the project. Depending on the size of the project the decomposition could include partial projects, deliverables and work packages.

Work packages form the lowest level of planning and consist of activities which are assigned to different individuals. Several work packages together result in deliverables and those might form partial projects which put together make up the end result of the project.

You do not list time components or dependencies in a WBS to keep a clear focus on the work to be done. A WBS should be created before a detailled project plan as it is a basis to estimate the resources needed and to create a cost and time schedule. What is not mentioned in the WBS, will not be part of the project's scope and therefore not be delivered.

Project Schedule

Gantt chart view in Merlin Project

Every project needs a project schedule. Without a solid schedule, your project won't succeed.

The project schedule communicates not only what needs to happen to complete the project but also shows when it needs to happen. It gives a clear view what work needs to be performed, who will be doing the work, which resources are necessary and in which time frame the work has to be accomplished. In this way, the project schedule generates a timeline and indicates when the project as a whole will be completed.

Project managers usually use project management software to integrate all data in one dynamic file which then can be updated depending on changes in resources and requirements during the course of the project.

To start scheduling a project you first need to ask yourself three questions:

. What needs to be done?
. When will it be done?
. Who will do it?

Take the WBS as a foundation. Look at all the different activities and determine the time and effort it will take to complete each task. Next, put the activities in a chronological order and make sure to take into account dependencies between different tasks. Some can't be started before others are completed. In the end, assign the necessary resources.

Scheduling a project is one of the hardest parts in project management but it is extremely important. The project schedule is an invaluable checklist for the project manager to keep the project on track.

Project Plan

A project plan establishes a general framework which guides all further planning. It is a formal approved document which defines how the project will be executed, monitored and controlled. Its primary use is to document planning assumptions and decisions, facilitate communication among project stakeholders, and document approved scope, cost, and schedule baselines. Usually, the plan is created as a text document with some illustration to visualize key aspects.

Important aspects a project plan usually covers:

  • Goals and objectives
  • Project scope
  • Milestones and timeline
  • Project organization, key roles
  • Cost plan
  • Quality management plan
  • Resource plan
  • Stakeholder management
  • Communications management
  • Project change management
  • Risk management approach
  • Descriptions of tools, technology and techniques

The project team and its key stakeholders should agree on and approve the project plan.

Conclusion

As the explanation above has shown, work breakdown structure, project schedule and project plan are distinct management tools and usually do not refer to the same concept. However, as there is no one uniform definition for neither of the terms, make sure everyone is on the same page when you refer to WBS, project plan or project schedule. It's commonplace but true: Clear communication is crucial for project success.

Project Management with a bit of Magic!

Merlin Project combines traditional methods with Kanban.