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2.5 Design2.5.1 The DIMA designIn [30], a generic agent structure for implementation in OO languages is proposed, based onactive objects. The definition of an agent is based on the one proposed by Wooldridge (e.g.[23]]). Characteristics are derived from that definition, including:- An agent’s behavior can be decomposed into several behaviors like perceiving,reasoning, communicating. Each of them can be procedural or knowledge-based.- An autonomous agent must have autonomous therefore concurrent behaviors. Besides,the communication behavior must incorporate a message interpreter (opposed to directmethod invocation) so that the agent keeps control over its internal state and behavior.- An agent is proactive so it must incorporate a meta-behavior that manages its set ofbehaviors, depending on its internal state and the external state of the world.- An agent is sociable so it has to understand a communication language.The proposed structure is this one:From [30]It is made of a first layer of concurrent behaviors that are managed by a Supervision Moduleat the meta-level (meta-behavior). This module is implemented as an Augmented TransitionNetwork where states represent decision points. These decisions are about activating orsuspending a behavior.The behaviors are modules that have their own data, methods and engine. The data can beupdated by the methods or any asynchronous event. The engine is a thread that controls theactivation of the methods. It can be interrupted by the Supervision Module between twomethod/rule firings. Examples of behaviors are deliberation, perception, communication. Abehavior is called reactive when it is purely procedural or cognitive when it is knowledgebased,e.g. when the engine is an inference engine. Thus the structure was implemented inSmalltalk-80 augmented with NéOpus for allowing rule-based programming.MSc EMOOSE Thesis – http://www.emn.fr/EMOOSE 22