Abstract: MAS/KIB——a multiagent system specification is built using mental states such as K(Know), B(Belief), and I(Intention), its grammar and semanteme are discussed, axioms and inference rules are given, some properties are researched. MAS/KIB has following characteristics: (1)Each agent has own world view; (2)No global data in the system; (3) Processes of state changes are used as indexes to systems; (4)It has the characteristics of not only time series logic but also dynamic logic; (5)Interactive actions are included.

Key words: specification, multiagent system, grammar