Use cases are commonly used to represent customers? requirements during systems development. In a large software development environment, finding a relevant use case from a large use case library created in the past or related projects is a complex, error-prone and expensive task. Based on the semantic web approach, we propose an ontological methodology to support this task. We use an ontology to augment use cases with semantic information. This ontology is derived from ResearchCyc ontology. We also propose the augmentation of queries used to retrieve use cases with this ontology. We present this approach to better capture, reuse and query use cases