wilamowski-b-m-irwin-j-d-industrial-communication-systems-2011

16-2 Industrial Communication Systems
16.2 agents and Multi-Agent Systems
16.2.1 Intelligent Agents Definition
Intelligent agents can be regarded as autonomous, problem-solving computational entities with social
abilities that are capable of effective proactive behavior in open and dynamic environments. There are
a number of different definitions of intelligent agents (cf. e.g., [1]); many of them associate the following
properties with an agent:
• Autonomy: An intelligent agent has control over its behavior, that is, it operates without the direct
intervention of human beings or other agents, and has control over its internal state and its goals.
• Responsiveness/Reactivity: An intelligent agent perceives its environment and responds in a timely
fashion to changes that occur in it in order to satisfy its design objectives/goals.
• Social ability: An intelligent agent is capable of interacting with other agents (and humans) and
will do so if that helps to achieve its design objectives/goals or organizational or combined goals.
• Intelligence: An agent has specific expertise and knowledge. Thus, it is capable of dealing with and
maybe solving problems that fall into its domain of expertise.
• Proactiveness: An intelligent agent is goal directed, deliberative, intelligent, opportunistic, and
initiative. Due to its goal-directed behavior, the agent takes initiative whenever there is an opportunity
to satisfy its goals. It especially may react proactively to changes in its environment; that is,
it responds to it without being explicitly asked for it from the outside.
The most popular model for cognitive, intentional agents is the belief-desire-intention (BDI) architecture
(cf. [36]). Here, agents react to changes in their environment with the help of practical reasoning.
Roughly speaking an agent comes with a number of sets. The beliefs reflect its abstracted understanding
of that part of the real world it is interested in. This understanding is subjective to the agent. The desires
represent the goals of the agent. In order to achieve its goals, an agent has to sense its environment and
react to relevant changes, usually by executing plans from its predefined set of plans/actions. Thus, a
reasoning process first identifies the affected goals and appropriate plans. Reasoning is enabled by conditions
that are annotated to plans and goals. The intensions of an agent are reflected by a data structure
that lists those plans/actions in an appropriate/ordered way an agent has chosen to execute as a reaction
to the last (and prior) relevant events in its environment.
16.2.2 Multi-Agent Systems
Due to the limited capabilities of a single agent, more complex real-world problems may require the
common and cooperative effort of a number of agents in order to get the problem at hand solved.
A multi-agent system (MAS) is a federation of fully autonomous or semiautonomous agents (problem
solvers) that are willing to join forces in order to achieve their individual goals and/or the overall
goals of the federation. In order to succeed, they rely on communication, collaboration, negotiation,
and responsibility delegation, all of which are based on individual rationality and social intelligence
of the involved agents. The global behavior of a MAS is defined by the emergent interactions among its
agents, which implies that the capability of a MAS surpasses the capabilities of each individual agent.
Reduction of complexity is achieved by (recursively) decomposing a complex task into a number of
well-defined subtasks, each of which being solved by a specific agent. However, unlike hard-wired
cooperation domains, these coalitions or teams are very flexible. Depending on the organizational
structure, agents may autonomously join or leave the coalition whenever they feel like—provided their
commitments are fulfilled.
For agents, in order to be able to cooperate, there is a need for communication. The most important
communication languages Knowledge Query and Manipulation Language (KQML, standardized
by Defense Advanced Research Projects Agency (DARPA) and agent communication language
© 2011 by Taylor and Francis Group, LLC