Conceptual modeling is an essential requirements engineering activity. Its objective is the development of the conceptual schema (CS) of an Information System (IS), which defines the general knowledge that an IS needs to know to perform its functions.
A CS consists of a structural (sub)schema and a behavioral (sub)schema. The structural schema consists of a taxonomy of entity types, a set of relationship types, and the constraints they must satisfy. The behavioral schema consists of a set of event types with their characteristics, constraints and effects.