Abstract The paper discusses some weaknesses in recently suggested models for information system specification. An augmenting, formal model of an information system is composed basing on the view that an information system essentially has a mediating role in the organizational discourse. This view permits the application of the speech act theory, and recent results in the organization theory. These general theories are adapted for information systems yielding a formal interpretation. It does not focus on the technical specification but on the formal structure of social interaction through an information system.