Inferring Trust Based on Similarity with TILLIT

A network of people having established trust relations and a model for propagation of related trust scores are fundamental building blocks in many of todays most successful e-commerce and recommendation systems. However, the web of trust is often too sparse to predict trust values between non-familiar people with high accuracy. Trust inferences are transitive associations among users in the context of an underlying social network and may provide additional information to alleviate the consequences of the sparsity and possible cold-start problems. Such approaches are helpful, provided that a complete trust path exists between the two users. An alternative approach to the problem is advocated in this paper. Based on collaborative filtering one can exploit the like-mindedness resp. similarity of individuals to infer trust to yet unknown parties which increases the trust relations in the web. For instance, if one knows that with respect to a specific property, two parties are trusted alike by a large number of different trusters, one can assume that they are similar. Thus, if one has a certain degree of trust to the one party, one can safely assume a very similar trustworthiness of the other one. In an attempt to provide high quality recommendations and proper initial trust values even when no complete trust propagation path or user profile exists, we propose TILLIT — a model based on combination of trust inferences and user similarity. The similarity is derived from the structure of the trust graph and users’ trust behavior as opposed to Mozhgan Tavakolifard Centre for Quantifiable Quality of Service in Communication Systems (Q2S), Norwegian University of Science and Technology (NTNU), Trondheim, Norway e-mail: [email protected] Peter Herrmann Department of Telematics (ITEM), Norwegian University of Science and Technology (NTNU), Trondheim, Norway e-mail: [email protected] Svein J. Knapskog Centre for Quantifiable Quality of Service in Communication Systems (Q2S), Norwegian University of Science and Technology (NTNU), Trondheim, Norway e-mail: [email protected]