Transaction Oriented Multi-Agent System

TOMAS [BR98] is a multi-agent architecture composed of mental, capability and execution components. Mental components include: beliefs that an agent has, messages that are passed between agents, goals that are to be achieved, events that have occurred and the intentions that are adopted. Capability components include : plans (recipes to perform different tasks) and intention instantiators (that query the current beliefs of the agent to determine the set of applicable intentions). Execution components consist of plan interpreters that invoke the different steps of the plan and the event intention manager(EIM). When an event occurs, the EIM invokes the intention instantiators and collects the set of applicable intentions. It then chooses the intentions to be executed and schedules them with the help of the different plan interpreters. The plan interpreter executes its plan as an ACID (atomic, consistent, isolated and durable) transaction thereby avoiding race-conditions and providing concurrency control for intentions performing conflicting operations. The effects of the transaction are committed using a two phase commit protocol so as to provide some amount of fault tolerance.

A problem with this architecture is that ACID transactions are not feasible for long term activities and the computational overhead introduced by the two-phase commit can be quite substantial.