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Abstract
This paper sets out to examine the feasibility of application of the fuzzy set theory in modelling the time scheduling uncertainty in a contemporary and dynamic project execution environment. As such, issues like activity duration uncertainty, resource availability and, finally, resource levelling are considered relevant and are examined herein. In this way, the research aims to contribute to a scarcely researched topic, namely that of the multi-project resource levelling question in projects with uncertain activity durations. A relevant modelling framework is proposed and it is concluded that the proposed methodology may be of particular interest to practical, real-world applications.
Keywords: Fuzzy Project Scheduling, Multiple Project Management, Resource Levelling.
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Introduction
Uncertainty in the Scheduling of Single Projects
The management of projects in an uncertain environment requires decisions that are based on inconsistent, vague and imprecise data. The shortcomings of traditional scheduling methods such as CPM and PERT, that employ deterministic or basic probabilistic views consent to the formulation of a more generic methodology meeting the real-world requirements for project scheduling that may not be modelled satisfactory by the above views. It should be noted that probability theory and fuzzy set theory are two distinct approaches; the former deals with random events by assigning probability distributions to the data whereas the latter deals with the imprecision of the data. Fuzzy Project Scheduling (FPS) is based on fuzzy set theory and is useful in dealing with circumstances involving uncertainty, imprecision, vagueness and incomplete data.
In terms of FPS, Prade (1979) was the first researcher to propose the application of fuzzy set theory in scheduling problems. Chanas and Kamburowski (1981) presented a fuzzy version of PERT which they named FPERT. Important research in Fuzzy Project Scheduling has been conducted by McCahon and Lee (1988), Chang et al. (1995), Mon et al. (1995), Hapke et al. (1994), Lorterapong and Moselhi (1996), Dubois et al. (2003), Bonnal et al. (2004), Chen and Huang (2007). Overall there have been about 40 papers published in major international journals addressing various aspects of this new scheduling approach. Guiffrida and Nagi (1998) provide an excellent overview of FPS.
In both traditional CPM and FPS the issue of resource availability limitations is extremely crucial. Hence, in such situations, resource...