Based on the plethora of proposals and standards for rule-based and logic-based reasoning for the Semantic Web, a key factor for the success of Semantic Web information systems, in general, and agents, in particular, is interoperability of reasoning tasks among multiple, heterogeneous web software entities exchanging rule bases to justify their positions.

EMERALD is an implementation framework for interoperable reasoning among agents in the Semantic Web, by using third-party trusted reasoning services. The advantage is that every agent can exchange its position justification arguments (i.e. rule set) with any other agent, without the need for all agents to conform to the same kind of rule paradigm or logic; the receiving agent can use an external reasoning service to grasp the semantics of the rule set, namely the set of the results of the rule set.

EMERALD is built on-top of the JADE multi-agent system. In EMERALD, reasoning services are “wrapped” by an agent interface, called the Reasoner, allowing other IAs to contact them via ACL (Agent Communication Language) messages. The Reasoner can launch an associated reasoning engine, in order to perform inference and provide results. Notice that the Reasoner is actually a service and not a fully autonomous agent. The only reason that we have provided an agent interface is to be able to integrate into the JADE MAS environment.

Currently, the following rule engines have been integrated:
http://lpis.csd.auth.gr/systems/emerald/