Context Management for Distributed and Dynamic Context-Aware Computing
Research in context-aware computing has produced a number of middleware systems for context management. However, development of ubiquitous context-aware applications is still a challenge because most current middleware systems are still focused on isolate
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Middleware for Context Management Based on Context Domains
Abstract Context management based on context domains is an approach for supporting interests of variable wideness in distributed and dynamic environments. Context domains establish distributed boundaries for both context modeling and management. The design of a distributed middleware based on this concept should address an architecture that enables efficient context-based interaction in both localized and distributed pairs of consumer–provider, protocols for discovering context management systems, and a suitable programming model for context-aware applications. In addition, the middleware should address some additional requirements, such as its usage in resource-constrained portable devices. Keywords Context management · Middleware · Context-aware computing · Open distributed systems · Distributed architectures
6.1 Introduction Chapter 4 presented an approach for context management that supports context interests of variable wideness. To demonstrate the feasibility of the proposed approach, this chapter presents a distributed middleware that implements the concept of context domains. In addition, the design of the middleware addresses some additional requirements, such as its usage in resource-constrained portable devices. This chapter is organized as follows. Section 6.2 presents the design rationale that drove the implementation of the middleware and the main assumptions adopted in design time. Section 6.3 presents the middleware architecture, services and protocols. Section 6.4 presents the cNode: a middleware instance that runs on each client device. Section 6.5 presents the context modeling approach and the mechanism for deploying new context types in the distributed architecture. Finally, Sect. 6.6 presents the programming model for context consumers and providers.
R. C. A. da Rocha and M. Endler, Context Management for Distributed and Dynamic Context-Aware Computing, SpringerBriefs in Computer Science, DOI: 10.1007/978-1-4471-4020-7_6, © The Author(s) 2012
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6 Middleware for Context Management Based on Context Domains
Fig. 6.1 Context broker
6.2 Design Rationale To enable seamless evolution of context types, the proposed middleware architecture makes use of stubs for each context type that embedded the code required for accessing and managing instances of the corresponding context type. These stubs are automatically generated from a XML-based specification of a context type (see Sect. 6.5). The underlying code is responsible for handling changes in the actual context type and context domain that the application is dealing with. From the perspective of applications, context access is strongly typed: i.e. the type of a context information, in terms of the corresponding language mapping, is defined at development time, so as applications can be statically prepared to recognize the type of a context information. Context subtyping is implemented as inheritance on the object-oriented paradigm. The translation of context types/instances to clas
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