Brief History of Scheduling
experience and history teach is this -
that people and governments never have learnt anything from history, or acted on principles deduced from it."
G W F Hegel (1770-1831): Introduction to Philosophy of History.
Keywords: Schedule, control, CPM, PERT.
A Brief History of Scheduling [P042]
The science of ‘scheduling’ as defined by Critical Path Analysis (CPA) will celebrate its 50th Anniversary in 2007. In 1956/57 Kelly and Walker started developing the algorithms that became the ‘Activity-on-Arrow’ or ADM methodology for DuPont. The program they developed was trialled on plant shutdowns in 1957 and the first paper on critical path scheduling was published in 1958. 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 published by Dr. John Fondahl in 1961 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 [ see: The Origins of Modern Project Management ].
The evolution of 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 thereby encouraging the widespread use of manual scheduling techniques, with only the larger (or more sophisticated) organisations being able to afford a central scheduling office and the supporting computer systems.
The advent of the ‘micro computer’ (ie, personal computer, or PC) changed scheduling for ever. The first commercial software for this class of computer was developed by Micro Planning Services in the UK running on an Apple II. Micro Planner v1.0 was released in 1980 after 14 months development [ see more on the history of Micro Planner ]. The first IBM PC was launched in 1981; although the definitive IBM XT was not launched until 1983. ‘Windows’ type operating systems became available in 1984 (Apple Macintosh) with ‘Windows v1.0’ (Microsoft) launched in November ‘85. The rapid spread of relatively cheap, easy-to-use’ PCs spawned dozens (if not hundreds) of PC based scheduling systems including TimeLine, CA Superproject and Primavera.
Most of the dominant scheduling software tools available today emanate from this period. By way of example, Primavera was founded in May 1983, the original software being converted from a mainframe batch entry system. Today Primavera is arguably the dominant ‘high end’ project scheduling tool world wide.
The evolution of PC based scheduling moved project controls from an environment where a skilled cadre of schedulers operating expensive systems made sure the schedule was ‘right’ (and the organisation ‘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 organisations.
This paper tracks the development of scheduling systems (with a particular focus on Micro Planner and Primavera) and looks at the way the evolving technology has changed the way projects are scheduled and managed.
Appendix A and B added post presentation based on additional information received.