An application context explicitly defines the set of application service elements, related options and any other information necessary for the interworking of Application Entities on an association. The usage of the application context is defined in PS 3.7.
Two Application Entities when establishing an association agree on an application context. The requestor of an association proposes an Application Context Name and the acceptor returns either the same or a different Application Context Name. The returned name specifies the application context to be used for this association. The offer of an alternate application context by the acceptor provides a mechanism for limited negotiation. If the requestor cannot operate in the acceptor's application context, it will issue an A-Abort request primitive. Such a negotiation will facilitate the introduction of future versions of the DICOM Application Entity.