Rationale of Project Management by Precedence Diagram Method

Work Breakdown Structure

The concept of Work Breakdown Structure (WBS) developed with the Program Evaluation and Review Technique (PERT) in the United States Department of Defense (DoD). PERT was introduced by the U.S. Navy in 1957 to support the development of its Polaris missile program. While the term “work breakdown structure” was not used, this first implementation of PERT did organize the tasks into product-oriented categories.

By June 1962, DoD, NASA and the aerospace industry published a document for the PERT/COST system which described the WBS approach. This guide was endorsed by the Secretary of Defense for adoption by all services. In 1968, the DoD issued “Work Breakdown Structures for Defense Materiel Items” (MIL-STD-881), a military standard requiring the use of work breakdown structures across the DoD.

In 1987, the Project Management Institute (PMI) documented the expansion of these techniques across non-defense organizations. The Project Management Body of Knowledge (PMBOK) Guide provides an overview of the WBS concept, while the “Practice Standard for Work Breakdown Structures” is comparable to the DoD handbook, but is intended for more general application.

Under a professional project management methodology, every single project being managed must have a WBS.  Without it, the project will take longer and the project will be negatively impacted.

According to PMI – A Work Breakdown Structure (WBS) is a deliverable-oriented grouping of project components that defines and organizes the total scope of the project; work not in the WBS is outside the scope of the project.

The backbone of any good schedule or budget is a well-rounded work breakdown structure that includes all work packages to fulfill the scope of the project requirements. A well-rounded work breakdown structure has the following characteristics:

– the entire scope of work is included
– the agreed work packages can be associated with both a cost (i.e. resourcing, materials, etc.) and a
– time (i.e. a start and finish time can be interpreted)
– the work package can be identified at the lowest level and each preceding level is within the scope of the project

Precedence Diagram Method

The term “precedence diagramming” first appeared around 1964 in the User’s Manual for an IBM 1440 computer program. One of the principal authors of the manual was J. David Craig of the IBM Corporation. Craig was also apparently responsible for naming the technique as “precedence diagramming method” (PDM).

This is a method of constructing a project network diagram using:

– nodes to represent activities and
– full arrows to show the dependencies.

Do you know that Precedence Diagram Method (PDM) is the method of choice for most project management software packages?

Common Scheduling Software in the market using PDM and WBS:

– MS Project 2019 by Microsoft https://www.microsoft.com/en-ph/store/cart
– Primavera P6 CPM Schedule by Oracle https://www.oracle.com/ph/industries/construction-engineering/primavera-p6/
– WBS Schedule PRO by Critical Tools https://www.criticaltools.com/