Activity definition

Activity definition is the dissection of the work breakdown structure from the project plan into parts whose duration can be meaningfully estimated.

Key Idea

Activity definition is describing the tasks that need to be performed in enough detail to estimate what resources and time will be required to complete them.


The lowest level of the work breakdown structure is known as the work package. Activity definition takes each work package and decomposes it further into schedule activities. These schedule activities are then used to form the foundation of the estimating, scheduling, executing, and monitoring and controlling of the project work. Simply put, activity definition is the breaking down of a project to the level where the duration of individual tasks can be estimated.

Inputs to activity definition

There are six inputs to activity definition:

  • The project scope statement.

  • The project management plan.

  • The work breakdown structure.

  • The work breakdown structure dictionary.

  • Organizational process assets.

  • Enterprise environmental factors.

The production of the first four inputs to the activity definition process have been described above. These define the project's deliverables and the steps required to achieve them. The project manager's task in activity definition is to divide these steps into a series of activities whose duration can be estimated in a manner that is consistent with the constraints of the organizational process assets and the enterprise environmental factors. Many a large engineering firm's projects have suffered serious schedule delays because project managers did not acknowledge that the organization's procurement system could not produce even simple items without several months' delay. The ability to recognize what is realistically achievable within an organization is crucial to the entire time management process.

Tools and techniques for activity definition

This ability to acknowledge what is and is not possible is often referred to as expert judgement. Expert judgement is one of five tools and techniques used during the activity definition process. The five are:

  • Decomposition.

  • Templates.

  • Rolling wave planning.

  • Expert judgement.

  • Planning components.

Decomposition is a planning technique that breaks the project scope and project deliverables into smaller components, until the project work is defined in sufficient detail to support executing, monitoring and controlling the work. The first experience the project manager has of decomposition is in the creation of the work breakdown structure to create the work packages. In activity definition the work packages are further decomposed to define the final outputs as schedule activities. Note the difference between the schedule activities created by this process and the deliverables from the creation of the work breakdown structure. It is usual for the team members responsible for each work package to undertake its decomposition.

In some cases similar projects may have been undertaken by the organization. In such cases, there may be templates of activity lists available to use on the new project.

Rolling wave planning is a method of planning immediate tasks in sufficient detail to enable work to proceed, while planning later work only to a high level in the first instance and not developing the detail until closer to the time of execution. This is particularly useful when detailed information affecting the later stages of a project becomes known only after earlier work is completed. In the decommissioning of nuclear power stations large savings have been achieved by deferring the planning of demolition work until a full survey of the hazards has been completed. This allows the safety case for demolition to be based on what the actual hazards are, rather than having to assume a more difficult to decommission, worst-case scenario.

Expert judgement comes from an individual or group who have specialist knowledge of the situation in hand. In the case of activity definition, the experts are likely to come from the project team members and other stakeholders who have had experience of this type of project before.

Two planning components are typically used in activity decomposition: control account and the planning package. These components are most successfully employed when there is insufficient decomposition of the project scope to provide a work package within the work breakdown structure. When this occurs the planning component can be used to create a high-level activity schedule for that branch of the work breakdown structure. This is likely to happen when an input to a phase of work is dependent on the unknown outcome of the preceding phases. For example, creating the scaled production process of a new pharmaceutical drug from the lab process can only be commenced once the lab process has been completed. A control account is a management control that integrates scope, budget, actual cost and schedule and compares them to earned value for performance measurement. A planning package is a level below that of the control account.

PMI says

Control account

'A Control Account is a managed control point where scope, budget, actual cost and schedule are integrated and compared to earned value for performance.' PMBOK Guide (p.355)


Activity definition outputs

There are four outputs from activity definition. They are:

  • The activity list.

  • The activity attributes.

  • The milestone list.

  • Requested changes.

The activity list contains all the schedule activities that are planned for the project. At this stage no schedules have been determined and neither have any dependencies. The activities in the list are assigned a unique identifying number, and a description of the scope of work they cover is recorded. This enables the team members to know which activity is being referred to and what exactly is expected to be accomplished during the activity, for example the design specifications for a piece of engineering, or the length of tarmac to be laid in road construction. The activity list is a component of the project management plan and the schedule activities are part of the project schedule.

Activity attributes provide greater information about the activities in the activity list, including activity descriptions, identifiers, predecessor and successor activities, logical relationships, resource requirements, lead times, lag times, constraints and assumptions; in other words, everything there is to know about the activity. These attributes are inputs to the schedule development process.

The third output is the milestone list. This is a list of the schedule milestones throughout the project. There are two types of milestones documented in this list: mandatory, such as being a contractual agreement; and optional, derived from the project requirements or historical information.

Requested changes is the last output from this process. It is likely that during the activity definition process changes to the project plan will be discovered. These changes must be formally documented and requested through the integrated change control process.

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Definitive Guide to Project Management. The Fast Track to Getting the Job Done on Time and on Budget
The Definitive Guide to Project Management: The fast track to getting the job done on time and on budget (2nd Edition)
ISBN: 0273710974
EAN: 2147483647
Year: 2007
Pages: 217
Authors: Sebastian Nokes
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