We explore common problems that exist in the practice of use case modeling: lack of consistency in defining use cases, misalignment between the UML metamodel and the textual representations of use cases expounded in the literature, and the lack of a semantics that allows use cases to be executable and analyzable. We propose an engineering approach to the issues that can provide a precise foundation for use case development. We next discuss four potential uses of such a foundation and identify the research problems that must be addressed to support these applications.