The word "context" is defined in the Merriam-Webster dictionary as "the interrelated conditions in which something exists or occurs". From the definition it is clear that context is always relative to something, and "context" denotes the relevant parts of the environment of the object under study.

In MUSIC we use context to denote the circumstances and conditions under which services provided by applications and other software systems (e.g. middleware) are being used. We partition context into three main groups:

• user context that relates to the user of a service;
• system context that encompasses the properties of the execution environment of an application;
• environmental context that reflects information concerning the object's surroundings such as position, weather, etc.

The complete set of context information can be quite rich but not all aspects of it are relevant for all services. The context may change during service usage. The MUSIC Middleware aims at adapting applications to varying contexts but also at enabling direct access of applications to context information.