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Within the domain of pervasive computing, context-awareness has commonly been defined as the ability of an application to adapt itself to its dynamic environment. The context of an application is defined as any information in the application's surroundings that may influence its current state or behaviour. Upon a change in the context, an application can either respond directly by invoking some functionality, or modify its behaviour for future interactions. The latter shows the need for context-dependent dynamic adaptation of application's behaviour.
In an interaction between two entities, however, the behaviour of the message receiver does not only depend on the context itself, but also on the context of the sender. We can illustrate this by envisaging a context-aware cell phone which notifies differently the incoming calls according to both the location of its user and the identity of the caller. These two facts belong to different contexts: the caller's identity is part of the caller's context whereas the callee's location is located in the callee's context. For better understanding of the context influence on the communication process between software entities, we refer the interested reader to the context-aware cell phone scenario.
In order to deal with context-dependent communications, we need a model that satisfies the following conditions:
Ambient references unify two concepts: they are both a peer-to-peer discovery channel and an asynchronous communication channel to a remote object.
- Composition of context-dependent application behaviours using prototype-based solutions (delegation hierarchies, split objects, subjective objects etc.). - Context-dependent adaptations of behaviour using role-based models. - Rule-based systems for context reasoning and role selection. - Role-based communications. - Combining actor and role models for the development of context-dependent applications. - Ad-hoc and intentional actor grouping. - Intra and Inter actor layers for context-dependent adaptations. - Dynamic scope for context-dependent communications.
A Role-Based Implementation of Context-Dependent Communications Using Split Objects. Jorge Vallejos, Peter Ebraert, Brecht Desmet. In “Proceedings of the workshop on Revival of Dynamic Languages, collocated with ECOOP 2006, Nantes, France”. [ download ]