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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 isolated and static context-aware environments. Context-aware environments are inherently dynamic as a result of occasional additions or upgrade of sensors, applications or context inference mechanisms.

Context Management for Distributed and Dynamic Context-Aware Computing proposes a novel architecture for context management based on the concept of context domains, allowing applications to keep context interests across distributed context management systems. The authors describe a distributed middleware that implements the aforementioned concepts, without compromising scalability and efficiency of context access.

Inhaltsverzeichnis

Frontmatter

Chapter 1. Introduction

Abstract
Research in context-aware computing has produced a number of application prototypes, frameworks, middleware systems and models for describing context. However, development of ubiquitous context-aware applications is still a difficult task because current middleware systems are focused on isolated and static context-aware environments. For example, applications require a global knowledge of the context-aware infrastructures in order to establish context-based interactions, and they suffer of problems such as disruptions when a context-aware environment evolves. This chapter introduces an approach for distributed context-aware computing that allows applications to maintain context-based continuous interactions, even in a dynamic environment. This chapter summarizes the limitations of current research in middleware for context-aware computing, as well the main contributions of this work.
Ricardo Couto Antunes da Rocha, Markus Endler

Chapter 2. Foundations of Context Management in Distributed and Dynamic Environments

Abstract
Context information is data that describes the state of a certain entity at a specific moment. A context management system is a computational element responsible for binding context providers, which produce context information, and context consumers, typically represented by context-aware applications. The main task of a context management system is to match consumer’s interests with probed context information. The complexity of context management in a distributed scenario is defined by the wideness of an interest, i.e. the number of context management systems that should be involved in an interest matching. If a distributed scenario is also open, heterogeneous and dynamic, than the wideness of an interest is variable, as a result of characteristics such as dynamic introduction of new sensors and evolution of context models. The support of context interest of variable wideness imposes challenging requirements for context management systems.
Ricardo Couto Antunes da Rocha, Markus Endler

Chapter 3. State of the Art

Abstract
Middleware for context management can be classified in four categories: distributed middleware systems, peer-to-peer context management systems, federation-based approaches and bridging approaches. Distributed middleware systems natively support distributed context management systems. Peer-to-peer context management systems creates the idea of distributions through connections between pairs of context management systems Bridging approaches use bridges to enable interoperability between pairs of heterogeneous context management systems. These approaches do not support context interest of variable wideness without compromising either the scalability of context management, the generality of context interests, or evolution of the environment’s context providers.
Ricardo Couto Antunes da Rocha, Markus Endler

Chapter 4. Domain-Based Context Management

Abstract
The support for context interests of variable wideness introduces several challenges for context management. First of all, consumers demand contextual interoperability, in order to enable the interpretation of a context interest across various context management systems. In order to support expressions of closed and open domain, a middleware must support address resolution of context management systems and enable the definition of context scope boundaries and their management. Context management based on context domains is an approach for supporting interests of variable wideness in distributed and dynamic environments.
Ricardo Couto Antunes da Rocha, Markus Endler

Chapter 5. Usage Scenario

Abstract
In distributed and dynamic context-aware environments, applications need to specify context interests of variable wideness. This chapter presents a scenario for a context-aware application in a distributed environment which considers migration cross networks, context domains, heterogeneity, and interaction with various context providers. The scenario demonstrates aspects of actual ubiquitous applications, such as interoperation across diverse environments of context-aware computing. The application is a location-aware messaging application, and it is applied to a tourist scenario.
Ricardo Couto Antunes da Rocha, Markus Endler

Chapter 6. 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.
Ricardo Couto Antunes da Rocha, Markus Endler

Chapter 7. Implementation and Evaluation

Abstract
The feasibility of the context domains approach for context management is demonstrated through an implementation of a distributed middleware. Test results have shown that the implementation’s performance is appropriate to the target scenario. The event engine of the middleware is based on a distributed event-based system called Naradabrokering. In particular, the middleware adopts Naradabrokering’s XML engine. Context information is represented as XML events, which the engine matches with context interests described in XPath expressions. This middleware allows the development of context-aware applications for mobile devices, and runs in two platforms: Android and Java J2ME CDC 1.1.
Ricardo Couto Antunes da Rocha, Markus Endler

Chapter 8. Conclusions

Abstract
Context management based on context domains is an approach for supporting interests of variable wideness, which is a fundamental requirement to context-aware computing in distributed and dynamic environments. This work explored this concept and presented three additional contributions: a primitive to describe context interests of variable wideness, the design and implementation of a middleware that support context domains, and a categorization of architectures for supporting distributed context-aware computing.
Ricardo Couto Antunes da Rocha, Markus Endler
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