This paper describes a project, called Gravity, that defines a component model, where components provide and require services (i.e., functionality) and all component interaction occurs via services. This approach introduces service-oriented concepts into a component model and execution environment. The goal is to support the construction and execution of component-based applications that are capable of autonomously adapting at run time due to the dynamic availability of the services provided by constituent components. In this component model the execution environment manages an application that is described as an abstract composition that can adapt and evolve at run time depending on available functionality. The motivation of Gravity is to simplify the construction of applications where dynamic availability arises, ranging from modern extensible systems to novel computing approaches, such as contrext-aware applications.