Consistency checking of UML requirements

This paper discusses how to check consistency of UML requirements model which consists of a use case model and a conceptual class model with system constraints. Based on a given semantics, the requirements consistency can be defined and checked formally. The consistency among use cases and constraints are classified into five types. A system operation of interaction between actor and system is formally defined as a pair of pre and post conditions. An atomic use case is described as one system operation, and a composed use case may be defined as several system operations described by an activity diagram. Thus, each use case can also be modelled as a pair of pre and post conditions by composing the pre and post conditions of system operations by introducing a sequence composition operation. Requirement consistency can be logically checked based on the semantics. A simple library system is used as a case study to illustrate the feasibility of the method.