Agent-based trust model involving multiple qualities

Abstract

A key limitation of current Web services standards is the inability to differentiate service instances at runtime using (nonfunctional) qualities of services (QoS). Such differentiation is necessary to allow for runtime selection and binding to service instances in a manner that continually adapts selected services to the service consumer's preferences and needs. Quality values are volatile, depend on the trust associated with instances and service providers, and also depend on the needs of service consumers. We propose a multiagent framework where agents consider the consumers' QoS preferences, determine trust levels to associate to service instances and providers, and automatically select service instances on a consumer's behalf. The service agents use a trust model that is centered on a shared conceptualization for QoS (ontology) and a QoS preference model that considers consumer's tradeoffs among qualities as well as relationships between qualities. We evaluate our approach via simulations on simplified but realistic service instances and service consumers. Our results show that using these considerations for QoS, service agents are able to determine over time the 'best' service selection for a consumer. Copyright 2005 ACM.