Enabling the ambient i n telligence vision means that consumers will be provided with universal and immediate access to available content and services, together with way of e ectively exploiting them. Concentrating on the software system development aspect, this means that the actual implementation of any a m bient intelligence application requested by a user can only be resolved at runtime according to the user's speci c situation. This paper introduces a base declarative language and associated core middleware, which supports the abstract speci cation of ambient i n telligence applications together with their dynamic composition according to the environment. The proposed solution builds on the Web Services Architecture, whose pervasiveness enables both service availability in most environments, and speci cation of applications supporting automated retrieval and composition.