Originally, use cases were informal modeling artifacts serving for specifying the requirements of computer-based systems in the early development phase. Last decade emphasizes the need for rigorous definition of semantics for use cases since discovering their impact during the whole development process. In this contribution, the semantics of use cases is directly obtained as a consequence of formal representation of use cases in the language of higher-order logic. The definition itself reveals the use case specifications as three level architecture which enables abstract specification of static structure at higher levels and more detailed description of a system's behavior at the lowest level. Often mentioned compactness issue of use cases, the interplay between static views that focus primarily on elicitation possible users of the system and corresponding dynamic views describing abstract behavior of the system is treated separately by adding extra information specifying participants which are, nevertheless, accessible from the whole use case hierarchy.