Strategies for Global Optimization of Temporal Preferences

A temporal reasoning problem can often be naturally characterized as a collection of constraints with associated local preferences for times that make up the admissible values for those constraints. Globally preferred solutions to such problems emerge as a result of well-defined operations that compose and order temporal assignments. The overall objective of this work is a characterization of different notions of global temporal preference within a temporal constraint reasoning framework, and the identification of tractable sub-classes of temporal reasoning problems incorporating these notions. This paper extends previous results by refining the class of useful notions of global temporal preference that are associated with problems that admit of tractable solution techniques. This paper also resolves the hitherto unanswered question of whether the solutions that are globally preferred from a utilitarian criterion for global preference can be found tractably. A technique is described for identifying and representing the entire set of utilitarian-optimal solutions to a temporal problem with preferences.