Partial Valuation Structures for Qualitative Soft Constraints

Soft constraints have proved to be a versatile tool for the specification and implementation of decision making in adaptive systems. A plethora of formalisms have been devised to capture different notions of preference. Wirsing et al. have proposed partial valuation structures as a unifying algebraic structure for several soft constraint formalisms, including quantitative and qualitative ones, which, in particular, supports lexicographic products in a broad range of cases. We demonstrate the versatility of partial valuation structures by integrating the qualitative formalism of constraint relationships as well as the hybrid concept of constraint hierarchies. The latter inherently relies on lexicographic combinations, but it turns out that not all can be covered directly by partial valuation structures. We therefore investigate a notion for simulating partial valuation structures not amenable to lexicographic combinations by better suited ones. The concepts are illustrated by a case study in decentralized energy management.