Resource - Constrained Project Scheduling A View on Recent Developments

Scheduling and sequencing is concerned with the optimum allocation of scarce resources over time. Scheduling deals with defining which activities are to be performed at a particular time. Sequencing concerns the ordering in which the activities have to be performed. The allocation of scarce resources over time has been the subject of extensive research since the early days of operations research in the mid 1950s. The result is a vast and not easy to digest literature and a considerable gap between sclaeduling theory and shop floor practice. Practioneus blame scheduling theoreticians to spend scarce research money for studying toy problenas such as sequencing a set of simultaneously available unordered jobs with lcnown durations on a never failing machine in order to optimize irrelevant objective f~~nctions. Theoreticians blame practitioners for their ignorance about the recent development~, theii-reluctance in applying useful theory, or their over-enthusiasm in applying scheduling procedures miles away from their natural field of application. Despite this mutual 'interest', the major issues largely remain unresolved ~ I I practice, and scheduling and sequencing problems remain the subject of intensive research. All this does not come by surprise. Scheduling and sequencing theory , more than any other field in the area of opcrations management and operations research, is characterized by a virtually unlimited num