We introduce a model for information systems specification which covers the spaces of data, semantic contexts, events, objects life-cycle, integrity constraints, and operating periods. For each one of these space we define a structure and its interpretation that allow to specify this particular aspect of the system. In this approach data and event structures are independent. It is the object life-cycle structure that binds processes to objects on which they operate. Semantic contexts make process and integrity constraints independent from the details of the data structure. The definition of operating period determine which integrity constraints are active and which processes are allowed to execute at a given time. When put together, these specifications form a global information system specification that can be checked for consistency and completeness and that can be used to predict global system's behavior.