ASK OCE — July 20, 2006 — Vol. 1, Issue 10
Fifty Years on the Critical Path
Engineering projects have been tied to schedules since the time of the pyramids, but the modern notion of project scheduling is only as old as spaceflight itself.
Though their origins are separate, the rise of modern scheduling has roughly paralleled the development of the space industry. In "A Brief History of Scheduling: Back to the Future,"
Patrick Weaver, the Managing Director of the Australian firm Mosaic Project Services, takes a look back at the genesis and evolution of Critical Path Analysis, which will celebrate its fiftieth anniversary in 2007.
Weaver traces the beginnings of modern scheduling to 1957, when mathematicians James Kelley and Morgan Walker put the finishing touches on algorithms that would become the ADM scheduling methodology for the DuPont Company. Their method was first applied to address the cost of plant shutdowns; they sought to solve the time-cost conundrum associated with plant shutdowns and restarts. Their analysis — done with the help of a UNIVAC
mainframe computer — showed that rather than merely flooding a project with labor to recover lost time, management could instead focus resource and effort on the "right" task to reduce the down time without significantly increasing cost. With Kelley and Morgan's new method, DuPont saved 25 percent on shutdowns. Their first paper on critical path scheduling was published in 1959.
Weaver points out that the evolution of scheduling coincided with advances in computer hardware and software. The first computers were colossal mainframes, and new schedulers often had to spend months learning to properly use them for CPA. By the 1980s, however, the PC revolutionized the field. PC-based scheduling was transformed from the hands of relatively few highly skilled and specialized mainframe schedulers to anyone who had the proper scheduling software package on a desktop computer.
This democratization of scheduling was not all for the better, in Weaver's estimation. Critical path schedules in the PC context became "islands of data" marooned on individual PCs, leading to a drastic decline in the quality of scheduling. Since then, the rise of computer networking has facilitated scheduling that employs centralized enterprise systems supported by project management organizations. Though such systems manage scheduling information centrally, the data are easily available to anyone with the proper web and network access.