Runtime Verification of Deontic and Trust Models in Multiagent Interactions
Osman, Nardine Zoulfikar
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In distributed open systems, such as multiagent systems, new interactions are constantly appearing and new agents are continuously joining or leaving. It is unrealistic to expect agents to automatically trust new interactions. It is also unrealistic to expect agents to refer to their users for help every time a new interaction is encountered. An agent should decide for itself whether a specific interaction with a given group of agents is suitable or not. This thesis presents a runtime verification mechanism for addressing this problem. Verifying multiagent systems has its challenges. It is hard to predict the reliability of interactions, in systems that are heavily influenced by autonomous agents, without having access to the agent specifications. Available verification mechanisms may roughly be divided into two categories: (1) those that verify interaction models independently of specific agents, and (2) those that verify agent models whose constraints shape the interactions. Interaction models are not sufficient when verifying dynamic properties that depend on the agents engaged in an interaction. On the other hand, verifying agent specifications, such as BDI models, is extremely inefficient. Specifications are usually not explicit enough, resulting in the verification of a massive number of permissible interactions. Furthermore, in open systems, an agent’s internal specification is usually not accessible for many reasons, including security and privacy. This thesis proposes a model checker that verifies a combination of a global interaction model and local deontic models. The deontic model may be viewed as a list of agent constraints that are deemed necessary to share and verify, such as the inability of the buyer to pay by credit card. The result is a lightweight, efficient, and powerful model checker that is capable of verifying rich properties of multiagent systems without the need for accessing agents’ internal specifications. Although the proposed model checker has potential for addressing a variety of problems, the trust domain receives special attention due to the critically of the trust issue in distributed open systems and the lack of reliable trust solutions. The thesis illustrates how a dynamic model checker, using deontic/trust models, can help agents decide whether the scenarios they wish to join are trustworthy or not. In summary, the main contribution of this research is in introducing interaction time verification for checking deontic and trust models multiagent interactions. When faced with new unexplored interactions, agents can verify whether joining a given interaction with a given set of collaborating agents would violate any of its constraints.