Clarity in semantics and a rich formalization of this semantics are important requirements for ontologies designed to be deployed in large-scale, open, distributed systems such as the envisioned Semantic Web. This is especially true for the description of web services, which should enable complex tasks involving multiple agents. As one of the first initiatives of the Semantic Web community for describing web services, OWL-S attracts a lot of interest and increases its user base even though it is still under development. Our contribution to the development of this ontology is to identify some of its problematic aspects and to suggest enhancements through alignment to a foundational ontology. However, the contribution of our work is not limited to the concrete results reported in this paper, but rather consists of examples of the benefits of alignment to foundational ontologies and a description of the method itself.