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

Industrial Agent Technology 16-5
issue directives to the subordinate agents of the holon. Thus, it may broker and/or supervise the interactions
between the subholons of that holon. The outbound interface of a mediator implements the interaction
of the holon with the rest of the agent society. The mediator can plan and negotiate for the holon on the
basis of the common plans and goals of its underlying agents.
All this three kinds of federation architectures permit to coordinate the system activity via facilitation
as a means of reducing overheads, ensuring stability, and providing scalability (cf. [6]).
16.2.7 How Agents Can Be Implemented
In order to implement communities of agents, several layers need to be realized. The lowest layers are
the network and communication layers that allow agents to abstract from their exact physical location
and to exchange messages. On the next level, the actual agent infrastructure needs to be provided, which
means that usually a number of different agent types need to be provided (the actual agents, broker
agents, white and yellow pages, etc.) as well as ontologies and agent life-cycle management services.
These first layers can be seen as syntactical layers in the sense that they do not reflect the actual intelligence
of the system—they just provide the necessary foundation for a MAS to function. Especially for
these “syntactical” layers, a significant number of commercial and academic agent construction tools
are available, providing a variety of services and agent models, the differences reflecting the philosophy
and the target problems envisioned by the platform developers. A reference for a broad number of
agent construction tools can be found on the AgentBuilder Web site (http://www.agentbuilder.com/
AgentTools) and in [28].
Java Agent DEvelopment Framework (JADE; cf. [27]) is perhaps the best-known FIPA (cf. [29])
compliant platform to develop agent-based solutions. It provides the mandatory components defined by
FIPA to manage the agent’s infrastructure, which are the agent communication channel (ACC), the agent
management system (AMS), and the directory facilitator (DF). The AMS agent provides white pages and
agent life-cycle management services, maintaining a directory of agent identifiers and states, and the
DF provides yellow pages services and the capability of federation within other DFs on other existing
platforms. The communication among agents is done via message passing. The messages are encoded
using the FIPA-ACL and their content is formatted according to the FIPA-SL (Semantic Language), both
specified by FIPA. Ontologies should be used to support a common understanding of the concepts of
their knowledge domain, passed in the messages’ content. Ontologies can be designed using a knowledge
representation tool, such as Protégé (see http://protege.stanford.edu/), and then translated into
Java classes according to the JADE guidelines that follow the FIPA Ontology Service Recommendations
specifications (cf. [29]).
JADE also provides a set of graphical tools that allows supervising the status of agents and supporting
the debugging phase which are usually quite complex tasks in distributed systems. Figure 16.1 illustrates
FIGURE 16.1
Graphical user interfaces of the Remote Monitoring and Sniffer agents.
© 2011 by Taylor and Francis Group, LLC