Communication Attitudes: A Formal Approach to Ostensible Intentions, and Individual and Group Opinions

Conventional approaches to the modeling of autonomous agents and agent communication rely heavily on the ascription of mental properties like beliefs and intentions to the individual agents. These "mentalistic" approaches are, when applicable, very powerful, but become problematic in open environments like the Semantic Web, Peer2Peer systems and open multiagent systems populated by truly autonomous, self-interested grey- or black-box agents with limited trustability. In this work, we propose communication attitudes in form of dynamic, revisable ostensible beliefs (or opinions) and ostensible intentions as foundational means for the logical, external description of agents obtained from the observation of communication processes, in order to retain the advantages of mentalistic agent models as far as possible, but with verifiable results without the need to speculate about covert agent internals. As potential applications, communication attitudes allow for a simultaneous reasoning about the (possibly inconsistent) "public image(-s)" of a certain agent and her mental properties without blurring interferences, new approaches to communication language semantics, and a fine-grained, statement-level concept of trustability. As a further application of communicative attitudes, we introduce multi-source opinions and opinion bases. These allow for the computational representation of semantically heterogeneous knowledge, including the representation of inconsistent knowledge in a socially reified form, and a probabilistic weighting of possibly indefinite and inconsistent assertions explicitly attributed to different provenances and social contexts.