History, State of the Art and Challenges for Agent Communication Languages

Knowledge Query and Manipulation Language (KQML) is a language of typed messages, usually understood as speech-acts, encoded as ASCII strings (in a LISP-like syntax), that are transported over TCP/IP connections, and aimed at knowledge and information exchange between software systems that are viewed as Virtual Knowledge Bases. KQML, which first appeared almost 10 years ago, has come to define the concept of an ACL and in the process the ACL has become the centerpiece of a large category of agent systems. Inevitably an ACL has become a loosely-defined concept that encompasses a variety of issues which may or may not be ACL-relevant depending on one’s point of view. The more “conservative” viewpoint advocates that the semantics of the message types is the one and only real issue. Agent development suggests though that semantics is the least important concern when one actually builds an agent system. The efforts of many researchers to develop multi-agent systems have brought to the foreground issues and considerations that are at least as important as the semantics for interoperable agent systems. After introducing some of the basic concepts relating to Agent Communication Languages, we cover KQML and FIPA ACL, the two existing fully-specified ACLs. We give a brief introduction to their semantics and the issues relating to semantic descriptions of ACLs. We then shift our focus beyond the semantics and point to emerging threads of research in the ACL community. The issues that we deem relevant to the widest possible acceptance of ACLs include alternative syntactic encodings, services and infrastructure, integration with the WWW, and specification of conversation protocols.