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research:context [2006/06/30 17:18]
jorge
research:context [2009/11/30 16:55] (current)
dharnie *prog->soft
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-===== Role-Based Ambient Communications =====+===== Context-Dependent Behaviour Adaptations ===== 
 +[[http://soft.vub.ac.be/~jvallejo/|Jorge Vallejos]]
  
-== Context-Dependent Communications in Ambient Intelligence ==+==== Motivation ====
  
-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.+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 or service in the application's surroundings that may influence its current state or behaviour. In this research, we focus on the influence of such context on the communications between the entities of a software system.
  
-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+Our observation is that in an interaction between two entities, the behaviour of the message receiver may not only depend on its own context, but also on the context of the sender. We have illustrated this idea in high level **[[research:context-aware_cell_phone|context-aware cell phone scenario]]**.
  
-As said in the presentation of this website, we are working on the field of pervasive computing. In such setting, context will play an important role. The context consists of all the information and services that are reachable by user devices at each given point in time. Examples include geographical location, time of day, temperature, other users in the environment, their respective context information, and so on. The software that runs on user devices is influenced by such context information, and the software should ultimately display different behavior according to the context of use.+We claim that in order to deal with context-dependent communications in mobile networks, we need model that satisfies the following conditions:
  
-In order for the receiver of a message to adapt its behaviour according to the context of the communication partners, the sender's context has to be passed in the message. However, this context should not get entangled with the functional behaviour of the receiver since this would inevitably lead to less understandable and maintainable code.+  * **Dynamic Context Adaptation**: Context information may influence the behaviour of a device. Applications should adapt to their context by dynamically switching of behaviour.
  
-  * **Dynamic Context Adaptation**: Context information may influence the behaviour of a device - it should signal incoming calls in different ways, give you services that are of importance to you in your current environment, and so onContext-aware applications should adapt to their context by dynamically switching of behaviour.+  * **Dynamic Behaviour Composition**: The resulting behaviour is typically a composition of possible different behavioursApplications should be based on composable parts representing partial context-dependent adaptations.
  
-  * **Dynamic Behaviour Composition**: The resulting behaviour is a composition of possible different behaviours - you don’t want the phone’s behavior to change completely, but only different variations of the same behaviorContext-aware applications should be based on composable parts representing partial context-dependent adaptations.+  * **Context Passing Mechanism**: It is not only the context of one device that determines its behavior, but also the context of other devices potentially play an important roleIn the case of context-dependent communications, the context information of the message sender should also be taken into account to decide the behaviour adaptation of the receiver. We require therefore a way to get acknowledgment of the sender’s context information.
  
-  * **Context Passing Mechanism**: It is not only the context of one device that determines its behaviour, but also the context of other devices potentially play an important role.+==== Design ====
  
-== Design ==+At our [[http://soft.vub.ac.be|lab]], we are currently exploring different language constructs for the development of context-aware applications. Here we present one of thes constructs called Split Objects (Bardou et al, ECOOP 1996). In such a model, application entities are composed of roles (known as viewpoints) which represent the different behaviours the entity can adopt. A role is a particular point of view on an entity that has an identification and a partial definition of that entity. The model's message sending protocol allows the specification of the role the receiver should adopt to respond to the message. Hence, if context-dependent behaviour is modelled as roles, an application could adapt to its context by just assuming the appropriate role.
  
-Ambient references unify two concepts: they are both a peer-to-peer discovery channel //and// an asynchronous communication channel to a remote object.+{{ rolemodel02.jpg?455x318| Click the image to enlarge }}
  
-== Ongoing and Future Work ==+The problem with the split objects model is that the message sender must know before hand which are the roles a receiver could take. In dynamic environments like mobile open networks, this acknowledgment is practically impossible and undesirable (due to the heterogeneity and autonomicity of the participants). Hence we have extended this model in such a way that the sender only have to include its own context information in the messages (and not a role). At the receiver side there will be a reasoning engine that will take as input the context of both sender and receiver, and will map this information to a role. We have called this entity the context-dependent role selector. For further information about this solution, we refer the interested reader to [ [[http://soft.vub.ac.be/Publications/2006/vub-prog-tr-06-17.pdf|this paper]] ].
  
-- Composition of context-dependent application behaviours using prototype-based solutions (delegation hierarchies, split objects, subjective objects etc.). +==== Ongoing and Future Work ====
-- 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.+
  
-== Implementation ==+These are the different research topics we have identified so far:
  
-A detailed explanation of ambient references can be found in [[ftp://prog.vub.ac.be/tech_report/2006/vub-prog-tr-06-07.pdf|this technical report]].+  * 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.
  
-== Further Reading ==+  * Rule-based systems for context reasoning and role selection.
  
-Ambient References: Addressing Objects in Mobile NetworksTom Van Cutsem, Jessie Dedecker, Stijn Mostinckx, Elisa Gonzalez Boix, Theo D'Hondt, Wolfgang De MeuterIn //Technical Report VUB-PROG-TR-06-10Vrije Universiteit Brussel//, 2006 [ [[http://prog.vub.ac.be/Publications/2006/vub-prog-tr-06-10.pdf|download]] ]+  * 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. 
 + 
 +==== Further Reading ==== 
 + 
 +**A Role-Based Implementation of Context-Dependent Communications Using Split Objects**. Jorge VallejosPeter EbraertBrecht Desmet. In "Proceedings of the workshop on Revival of Dynamic Languages, collocated with ECOOP 2006, Nantes, France"[ [[http://soft.vub.ac.be/Publications/2006/vub-prog-tr-06-17.pdf|download]] ]
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