Large decentralized networks, e.g., the Semantic Web, peer-to-peer and ubiquitous computing, require approaches to security that are scalable, subjective and reliable. Hence, soft-security notions like trust and trust propagation, conceived as computational means to evaluate trust relationships between individuals, come into play.

Our major contributions to decentralized trust management through this paper are twofold. First, we introduce our classification scheme for trust metrics along various axes and discuss advantages and drawbacks of existing approaches for suchlike scenarios. Hereby, we will devise our advocacy for local group trust metrics, guiding us to the second part which presents Appleseed, our novel proposal for local group trust computation. Compelling in its simplicity, Appleseed borrows many ideas from spreading activation models in psychology and relates their concepts to trust evaluation in an intuitive fashion.