What is a Work Breakdown Structure?
The work breakdown structure is a hierarchical framework for organizing & ordering the activities that make up the entire project scope. It should cover all project scope & be broken down into “unique and manageable parts that correspond to key deliverable, phases of work, or milestones. Development of a WBS begins with decomposition of the project scope of work. This process breaks down the entire scope into discrete elements for which work can be planned and managed effectively.
The WBS typically consists of two components:
Levels – These establish the hierarchical structure of the work breakdown structure. Typically the highest level of the WBS is identified as level 0 or level1.
Elements – A discrete member of the WBS at each level of the hierarchy. It may be referred to as a node. At this level it represents the scope of work or task to be performed. The lowest level of any branch of the WBS is defined by the project requirements including estimating & control.
WBS dictionary: The WBS dictionary describes each of the work elements. It may include milestones, deliverables, activities, scope, dates, resources, costs and requirements. Includes: End result or expected work product, Relationships and dependencies between elements of work, Optional Elements (Risk factors, Assumptions or limitations, Tech. specifications, other supporting docs.) WBS provides a decomposition of the scope of work, it is product (deliverable – based) or process oriented, it established the basic building blocks for the planning, it establishes a common frame of reference for aligning cost estimating, scope control, project control etc…
Schedule Classifications:
It defines the project & engineering definition & degree of completeness required for schedule development.
Schedule Levels: It establishes the level of detail required for communication, reporting (for all levels of management) & execution. The schedule class designations are labeled Class 1, 2, 3, 4 & 5. A Class 5 schedule is based upon the lowest degree of project definition & a Class 1 schedule is closest to full project definition & maturity.
Class 5 Schedule: (Degree of project definition required: 0% to 2%)
Class 5 schedules are generally prepared based on very limited information, and subsequently have wide accuracy ranges.
Class 5 schedules are prepared for any number of strategic business planning purposes. Top down planning using high level milestones and key project events.
Class 4 Schedule: (Degree of project definition required 1% to 15%)
Class 4 schedules are generally prepared based on limited information & subsequently have fairly wide accuracy ranges.
The class 4 schedule should define the high level deliverable for each specific stage going forward. This document should also provide an understanding regarding the timing of key events. A high level WBS may be established at this time. Top down planning using high level milestones and key project events. Semi detailed.
Class 3 Schedule: (Degree of project definition required 10% to 40%)
Class 3 schedules are generally prepared to form the basis of execution for budget authorization, appropriation, and / or funding. As such, they typically form the initial control schedule against which all actual dates and resources will be monitored.
The class 3 schedule should be a resource loaded, logic driven schedule developed using the precedence diagramming method (PDM). The schedule should be developed using relationships that support the overall true representation of the execution of the project. The amount of detail should define, as a minimum, the work package (WP) level (or similar deliverable) per progress type/ unit and any intermediate key steps necessary to determine the execution path (The WP rolls up into the predefined WBS). They are used as the project schedule until replaced by more detailed schedule. Package top down planning using key events. Semi-detailed.
Class 2 Schedule: (Degree of project definition required 30% to 70%)
Class 2 schedule are generally prepared to form a detailed control baseline against which all project work is monitored in terms of task starts and completions and progress control.
The class 2 schedule is a detailed resource loaded logic-driven schedule that should be developed using the critical path method (CPM) process. The amount of details should define as a minimum, the required deliverable per contract per work package (WP). The schedule should further define any additional steps necessary to determine the critical path of the project necessary for the appropriate degree of control. They are used as detailed control baseline against which all actual start and completion dates and resources monitored for variations to the schedule, and form a part of the change/ variation control program. Bottom up planning. Detailed.
Class 1 Schedule: (Degree of project definition required 70% to 100%)
Class 1 schedule are generally prepared for discrete parts or sections of the total project rather than generating this amount of detail for the entire project. The updated schedule is often referred to as the control schedule and becomes the new baseline for the cost/ schedule control of the project.
The class 1 schedule may be a detailed, resource loaded, logic-driven schedule and is considered a production schedule used for establishing daily or weekly work requirements.
Class 1 schedule are typically prepared to form the current control schedule to be used as the final control baseline against which all actual start and completion dates and resources be monitored for variations to the schedule, and from a part of the change/ variation control program. They may be used to evaluate to support vendor/ contractor negotiations, or claim evaluations and dispute resolution. Bottom up planning. Detailed.
Identification of activities:
Identification of activities in schedule planning & development provides guidelines for the conversion of scope definition to specific activities and tasks required to complete a project. Identification of activities is a key planning step that takes place early in the schedule planning & development process which also includes estimating duration, identifying external project constraints, determining and defining resources. To begin the planning process, information in the scope documents must first be translated into manageable activities.
Review of Scope documents & supporting information, which may include the following:
Statement of work, Functional requirements, Project concept documentation (including all appropriate contract drawings and technical specifications), Work breakdown structure (WBS), Significant project milestones and constraints, Project estimate (including preliminary schedule of values), Risk analysis information including appropriate regulatory considerations that may affect the schedule, Project procurement/ contracting plan. (Long lead items), Lessons learned from previously completed similar projects.
At the conclusion of the schedule planning sessions, the list of activities should be reviewed for completeness. That review should include:
- Does the list of schedule activities include the entire project scope?
- Have all major & long lead time procurement been included?
- Is the level of detail appropriate for the project phase, complexity, and risk?
- Can all activities be summarized according to the WBS?
- Does each activity have a single responsible and accountable individual?
- Have specialists been consulted for unique requirements?
- Have past project history and lessons learned been considered?
- Is each activity capable of being measured and uniquely identified?
- Have all significant project milestones been included?
- Have all activity assumptions been documented?
- Have external constraints and drivers been considered?
During the activity planning process, it is critical that all work performance assumptions are clearly documented. Also, project scope interpretations, inclusions, and other basis information should be documented. This documentation will help reduce the risk of error or misapplication in subsequent schedule development. Eventually, these assumptions will become a part of the written schedule basis document.
Milestones: Milestones are unique events with no duration that mark significant points in project execution.
Summary Activities: Summary activities are a special grouping of activities that acquire the duration of the period of time between the predecessor and successor activity of the summary activity. They should be used only for summarizing a linked series of activities that occur between the span of the first predecessor and last successor activities. Summary activities are useful for presenting higher level graphics and tabular reports of discrete date.
WBS: The work breakdown structure (WBS) is a work categorization tool used for planning, managing, executing & reporting for the project. Therefore, the WBS should be a major reference source during the planning process, especially for identifying activities. Each activity must have only one WBS designation.
Duration of Project: Shorter duration projects typically require less level of detail than a longer duration project. As a general guideline, activity durations should be approximately the same length as the project’s planned frequency of progress status reporting.
Project complexity: Complex projects may have short durations, such as maintenance outages measured in hours, but may still require a greater level of detail in activity identification.
Execution Methodology: Projects with a high level of sub-contracting generally require less detail than self-performed projects.
Phase of project: The level of detail in activity identification should match the type of work being performed, & the information available for that phase.
Cost of Project: Generally, the higher the cost of the project, the greater level of detail in activity identification.
Ability to adequately review the schedule: The owner of a project should not require the submission of a schedule that is more detailed and complex than the owner is able to properly review. The owner is responsible for a reasonable understanding of the contents.
Cost of maintaining schedule: A higher level of detail in activity identification typically results in increased cost of maintaining and statusing the schedule.
Client Expectations: The client/ owner may have specific schedule requirements that may determine the level of detail required in activity identification.
Project Risk: Typically high risk projects are planned in detail to assist in risk mitigation.
Measurable: When identifying activities, the team should ensure that every activity can be easily measured & uniquely controlled.
Rolling wave planning: “Rolling wave” is schedule planning and development method in which near-term activities are planned in more detail than later term activities. As the near term work or program is executed, the team will identify the subsequent detailed activities that are required and replace the corresponding summary activity “place holders”. Rolling wave planning is an activity planning technique reserved for experienced schedulers working on long term/ complex ventures.
Developing Activity Logic:
Development of activity logic (network logic) for the sequencing of activities in a logical way generally before duration estimating can be performed. Logic development methods include precedence diagramming, or arrow diagramming methods. Logic is the set of activities and dependency relationships between them. Logic dictates the planned sequencing of activities. A network diagram is often used to illustrate the logic.
Planning & scheduling are not the same. Planning is determining how the work will be done, while scheduling is the analysis & calculation of start & finish dates. Logic enables the combination of activities to be arranged in one of the aforementioned formats so that a completion date can be established. Logic also enables backward passes to arrive at optimal overall schedule duration.
When should you Develop Logic:
Logic development is an iterative planning process. Initial logic development is begun after identification of activities, and before the scheduling process step occurs. This process is further refined duration schedule development & optimization. Generally, logic development starts with an activity list. Activities can be linked with hard logic (i.e. sequence of each activity is predetermined, such as footing form-work must be in place before concrete can be placed) or soft logic (such as footing A before footing B) wherein related activities may be combined & accomplished in a different order as determined at the time of execution. Development of activity logic is a pure planning step where relationships are established regardless of the dates on which activities fall.