Unifiable Preference Expressions for Pervasive Service Composition

Composing services in a pervasive environment usually involves user-in-the-loop adaption which is absent in most of the traditional enterprise service composition mechanisms. In such environment, the criteria for selecting and ranking services are usually specified by users, which tend to be vague and subjective. The criteria can be contradictory and the activated services can interfere with one another. This paper addresses these issues by defining a unifiable and negotiable expression language called the Preference Expression that is capable of specifying both enumerative/numeric as well as mandatory/negotiable user preferences. A set of unification rules for possible conflicting preferences is also derived. Experimental results show that the proposed approach is able to achieve high composition precision and maintains reasonable success rate at the same time.