Before embarking on our journey to understand the mentioned terms, let’s understand Decomposition

Decomposition as a means of breaking down scope into work package or work packages into smaller activities

I understand that for many of us, the project manager it doesn’t make a lot of sense to have two activities as we usually deliver both in Single sitting and also as one document without a very clear demarcation between WBS and activities.  Well! yes on small projects, the difference doesn’t matter much. But, as things get more complicated, it’s crucial to understand the difference and to do a good job creating each one.

WBS

Work Breakdown Structure (WBS) is a fundamental project deliverable that arranges the team’s work into manageable divisions. According to the Project Management Body of Knowledge (PMBOK), a work breakdown structure refers to deliverable-oriented classified decomposition of the work to be accomplished by the project team. WBS visually defines the scope in manageable units that a project team can comprehend with every level of the work breakdown structure providing extended definition and detail. Though it covers all the work in the work and only the work required but it’s not a contractual agreement.

The project team typically develops the project work breakdown structure by determining the key functional deliverables and dividing those deliverables into further systems and sub-deliverables. WBS helps to focus on communication and accountability at a level of detail required to manage a project. These sub-deliverables are eventually decomposed until only one person can be assigned. At this point, the particular work packages are needed to produce sub-deliverables that are identified and assembled together.

The work package signifies the list of tasks to accomplish a certain unit of work. If you are familiar with any detailed project schedules, then you will probably recognize the tasks under the work package that needs to be completed with a specific level of effort and in the allocated time frame.

Work packages refer to the lowest unit of work that a project can be segmented when developing your Work Breakdown Structure (WBS).

From a cost viewpoint, the work packages are often put together and allocated to a particular department to carry out the work. These departments or cost accounts are referred to as an organizational breakdown structure. They are provided a specific budget to produce the defined deliverables. By incorporating the cost accounts from the managerial breakdown structure and the project’s work breakdown structure, the whole business is capable of tracking the financial progress in addition to overall project performance.

WBS covers all the deliverable and all the work needed to be delivered on the Project

WBS is part of the Planning process group and falls into Project Scope Management.  WBS is developed to establish a common understanding of project scope.

Activity

An activity is referred to as the scheduled phase in a project plan with an individual beginning and end. An activity typically comprises multiple tasks and upon completion, the entire activity is completed. Many activities can be combined leading to the summary activity. The duration of an activity can be figured out by considering the effort it takes to complete the designated tasks. The beginning and end of the activity are also determined by limitations commonly known as dependencies. In addition to that, the milestone is another determining factor. These dependencies between activities and other planning factors are visualized and estimated in a Gantt diagram. This is often used by project managers to plan tasks and monitor their progress.

The work packages are disintegrated into scheduled activities to create an activity list. This activity list is used in developing the project schedule. An activity has an anticipated duration. In case an event has no time period, it is referred to as a milestone. The work package is the lowest level of deliverables in a project. It’s an outcome of an endeavour.

They are an important part of the project satisfying the tasks and offering value to the stakeholders. On the other hand, a series of activities result in the work package. It’s one imperative step of the endeavour. An activity neither provides value to the stakeholders nor is handed over to the project stakeholders.

This is part Planning process group and falls into Project Schedule Management

Example:

Consider a Software Development Project. Let suppose the project team has developed WBS with software modules as work packages. Incorporation of all modules will result in the accomplishment of the software product. For instance, one module is “Module Y”, it would refer to a work package. Project Team will carry out a sequence of activities to create “Module Y”. These activities may include algorithm writing, coding, testing, integration etc. Project Team will repeat these activities until the final “Module Y” is created.

Differences

• A WBS is a list of the components of the deliverable.**
• An Activity List is a list of the activities we will engage in during the project.**
• The WBS is created as the finest level detail of defined project scope, after progressive elaboration**
• the first step in detailed time and cost estimation is the creation of the Activity List.**
• WBS is decomposed to the smallest level of deliverable i.e Work Package. This level is valued by stakeholders and properly recognized as deliverable
• Activities are action sequence to deliver the Work Package, the lowest level of WBS
• WBS components have tangible values and can be handed over to the Stakeholders
• The activity list is used for Scheduling in Scheduling Softwares like MS Project or Primavera to create a Gant Chart. It needs resources & has a time frame.

The WBS has to do with the project’s WHAT, while the schedule deals with the project’s HOW and WHEN.

Further Readings

1. Control Account, Work Package, Planning Package
2. Effort vs Duration vs Schedule
3. Product Scope vs Project Scope
4. Breakdown Structure for Project Management**
5. Project Scope Management
6. Work Breakdown Structure (WBS)