It is now widely recognised that methods are needed for coveting the whole lifecycle of Computer Integrated Manufacturing (CIM) applications. In this paper, we deal with the requirements engineering phase of this lifeeycle. A formal language is introduced for capturing real-time requirements expressed on CIM applications. The resulting speeitication is structured as a society of 'agents', each of them being charactefised by (i) its responsibility with respect to changes happening in the system and (ii) the perception of the behaviour of other agents. On top of illustrating the use of the language on a small case-study, we also suggest some methodological guidance in the elaboration of requirements for large CIM applications. KEYWORDS: O-O requirements engineenng, agents, actions, formal language, CIM applications, elaboration of the requirements document.* The input stock can neverbe empty. * A rivet cannot stay indefinitely in the input stock.