Concurrency and knowledge-level communication in agent languages

In this paper we try to answer the following questions: Is it possible to program solely at the level of an agent communication language? And if this is the case, what requirements and conditions need to be taken into account? We argue that, although a number of languages defining abstract communication primitives have been proposed in the past few years, knowledge-level programming can only be supported if a number of careful assumptions about the communication primitives and the underlying architecture are made, including asynchronous communication mechanisms, reliable message passing, and nonblocking primitives. To achieve a more rigorous understanding of these issues we proceed in a formal way. First, we postulate a set of requirements that an agent communication language should satisfy to be regarded as knowledge level. Then, we define a weak agent communication language, and we show that a synchronous Version of the language does not satisfy requirements for knowledge-level programming. Finally, we show how an alternative asynchronous version of the language can be defined, which avoids the aforementioned problems. To prove these results, we introduce a general framework for reasoning on communication and concurrency aspects in the context of agent communication languages. (C) 1998 Elsevier Science B.V. All rights reserved.