A Brief History of Scheduling
CRITICAL PATH ANALYSIS
Valuable research was done by Mr Patrick Weaver, The Managing Director of Mosaic Project Services Pty Ltd, in Melbourne Australia, on the history of scheduling. He has graciously allowed us to insert a copy of his material in this book, proving his passion for the training and development of Project Planners. We include his introductory comments in the main body of the book, and the complete paper is included in APPENDIX 1.
The science of “scheduling” as defined by Critical Path Analysis (CPA) celebrated its 50th Anniversary in 2007. In 1956/57 Kelly and Walker started developing the algorithms that became the “Activity-on-Arrow” or ADM scheduling methodology for DuPont. The schedule they developed was trialled on plant shutdowns in 1957 and their first paper on critical path scheduling was published in March 1959. The PERT system was developed at around the same time but lagged CPM by 6 to 12 months (although the term “critical path” was invented by the PERT team). Later the Precedence (PDM) methodology was developed by Dr. John Fondahl; his seminal paper was published in 1961 describing PDM as a “non-computer” alternative to CPM. Arguably, the evolution of modern project management is a direct consequence of the need to make effective use of the data generated by the schedulers in an attempt to manage and control the critical path.
THE EVOLUTION OF CPM
The evolution of CPM scheduling closely tracked the development of computers. The initial systems were complex mainframe behemoths, typically taking a new scheduler many months to learn to use. These systems migrated to the “mini computers” of the 1970s and 80s but remained expensive, encouraging the widespread use of manual scheduling techniques, with only the larger (or more sophisticated) organizations being able to afford a central scheduling office and the supporting computer systems.
The advent of the “microcomputer” (i.e. personal computer, or PC) changed scheduling forever. The evolution of PC based scheduling moved project controls from an environment where a skilled cadre of schedulers operating expensive systems made sure the scheduling was “right” (and the organization “owned” the data) to a situation where anyone could learn to drive a scheduling software package; schedules became “islands of data” sitting on peoples’ desktops and the overall quality of scheduling plummeted.
Current trends back to “Enterprise” systems supported by PMOs seem to be redressing the balance and offering the best of both worlds. From the technology perspective, information is managed centrally, but is easily available on anyone’s desktop via web enabled and networked systems. From the skills perspective PMOs are re-developing career paths for schedulers and supporting the development of scheduling standards within organizations. This paper tracks the development of scheduling and looks at the way the evolving technology has changed the way projects are scheduled and managed.
It is the aim of the authors that, by mastering the techniques outlined in this book, and with some solid practical project scheduling experience, the readers will become better Project Planners. This should restore some of the lost scheduling quality resulting from the introduction of scheduling software, as postulated by Mr Patrick Weaver. The authors are also of the opinion that the lack (or scarcity) of proper training programs, contribute to poor scheduling quality.
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