Semantic service descriptions have paved the way for flexible interaction with services in a mobile computing environment. Services can be automatically discovered, invoked and even composed. On the contrary, the user interfaces for interacting with these services are often still designed by hand. This approach poses a serious threat to the overall flexibility of the system. To make the user interface design process scale, it should be automated as much as possible. We propose to augment service descriptions with high-level user interface models to support automatic user interface adaptation. Our method builds upon OWL-S, an ontology for Semantic Web Services, by connecting a collection of OWL-S services to a hierarchical task structure and selected presentation information. This allows end-users to interact with services on a variety of platforms.