Constraint-based methods for scheduling discretionary services

  • Authors:

  • Xiaofang Wang;Nicola Policella;Stephen F. Smith;Angelo Oddi

  • Affiliations:

  • (Correspd.) School of Business, Renmin University of China, Beijing, China. E-mail: xiaofang.wang@gmail.com;European Space Operations Centre, European Space Agency, Darmstadt, Germany. E-mail: nicola.policella@esa.int;The Robotics Institute, Carnegie Mellon University, Pittsburgh, PA, USA. E-mail: sfs@cs.cmu.edu;ISTC-CNR, Institute for Cognitive Science and Technology, National Research Council of Italy, Rome, Italy. E-mail: angelo.oddi@istc.cnr.it

  • Venue:
  • AI Communications
  • Year:
  • 2011

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Abstract

A project network composed of discretionary tasks typically exists in service professions, such as journalism, clinic, software development or financial analysis, where the quality (or value) of a task increases with the time spent on it. Since a longer task duration consumes more resources (i.e., workers' time), the project manager must strike a balance between quality and time by scheduling tasks and setting their durations while respecting the project deadline, precedence and resource constraints. We formulate this problem, give a polynomial-time optimal algorithm for the single capacity case and prove the NP-completeness of the general multiple capacity case. Then we develop two hybrid solution procedures integrating linear optimization and an AI search procedure - precedence constraint posting - for the general case. Our results verify the effectiveness of these procedures and show there exists a potential synergy between objectives of maintaining temporal flexibility and maximizing quality, which implies that existing techniques in building flexible schedules can be adapted to solve this new class of problems.