A Z-Specification of Classification and Relationships between Usecases

Usecases are widely used to decompose and describe functional requirements of software systems. They do not capture non-functional requirements which describe orthogonal properties and restrictions of systems. Relationships between use cases are described using UML stereo types extend and include. These two stereo types are not adequate to capture many-to-many relationships between functional and non-functional requirements. In this paper, we present a Z-specification for use cases to capture both functional and non-functional requirements and relationships between them. We define an abstract usecase schema which is specialized to concrete, generalization, extension, inclusion and aspect usecase schemas. The dependency relationships among these schemas are classified as: include, extend and crosscut. These relations are defined in terms of event sequences.