Abstract
M.Sc.(Computer Science)
The dissertation investigates trust and reputation as a specialisation of agent
technology. The research presented herein aims to establish and demonstrate how it is
possible for one rational agent to trust another entity. Furthermore, the research
presented herein aims to determine the extent of the limitations of trust and reputation
models, and of the demonstrable solution in particular. To this end, the dissertation
investigates theoretical aspects of trust. The dissertation investigates several existing
trust models and establishes criteria for a qualitative analysis. Supplementary
techniques aimed at enhancing trust evaluation are also investigated. The research
also identifies architectural abstractions suitable for developing agents capable of
intelligent trust evaluation. The main focus of the research is enhancing agent
protection through a trust-based approach. A particular problem is the threats posed to
mobile agents from malicious agent hosts. Therefore, a solution is sought that can be
used to augment existing mechanisms aimed at mobile agent protection and agent
protection in general. Thus, the research also examines mobile agents and mobile
agent systems in an effort to produce a general trust-based solution that can be applied
in most mobile agent systems. The solution presented in the dissertation proposes the
concept of an evaluator agent as an add-on to existing mobile agent systems. The
evaluator agent is presented as a rational agent with an embedded intelligent trust
evaluation capability. The intelligent trust evaluation capability is provided via a set
of reusable components. The solution demonstrates how a rational agent may evaluate
the trustworthiness of other entities. The dissertation further analyses the strengths
and limitations of the approach. The dissertation provides results that quantitatively
demonstrate the extent of the limitations of the trust-based approach. The contribution
of the dissertation partly lies in the service orientation of the evaluator agent
approach. The service orientation of the solution provides an abstraction and a degree
of heterogeneity suitable for handling the challenges of open environments. The
solution can be deployed in most mobile agent systems to provide a trust evaluation
service without the need to redesign existing mobile agent systems. More broadly, the
research is another step towards the development of cognitive social agents.