Abstract. Connectors and connector wrappers explicitly specify the protocol of interaction among components and afford the reusable application of extra-functional behaviors, such as reliability policies. Ideally, these specifications can be used for more than just modeling and analysis. We are investigating how to use them in the design and implementation of the middleware substrate of a distributed system. This paper reports our experience elaborating connectors and connector wrappers as instantiations of a feature-oriented middleware framework called Theseus, which supports the design of asynchronous distributed applications. The results of this case study indicate that the relationship between specification features and implementation-level features is not one-to-one and that some specification features have complex, often subtle, manifestations in Theseus ’ design. This work reports the lessons learned designing these strategies and suggests techniques for designing middleware frameworks and composition tools that more explicitly reify and expose the features specified by connectors and connector wrappers. 1