Because of the growing diversity of mobile computer terminals and communicating objects, we observe the emergence of applications using the notion of context. Firstly, we propose an analysis of definitions of context. Then, we present a model in which we simplify the expression of the problems caused by the interaction between the computer, the user and their environment. We also give the definition of the notion of proximity between entities in a multi-dimensional space and apply this notion to the previous model. Proximity of an entity refers to verify some conditions in a certain context. If the conditions are verified, some modifications and adaptations must be made at the application level. We propose an innovative software adaptation based on aspects of assemblies and dynamic reconfiguration of applications.