Context-Aware Service Discovery in Ubiquitous Computing
Huaqun Guo (Institute for Infocomm Research and National Univerity of Singapore, Singapore), Daqing Zhang (Institute for Infocomm Research, Singapore), Lek-Heng Ngoh (Institute for Infocomm Research, A*STAR, Singapore), Song Zheng (Institute for Infocomm Research, Singapore) and Wai-Choong Wong (National University of Singapore, Singapore)
Copyright: © 2008
The decreasing cost of networking technology and network-enabled devices is driving the large scale deployment of such networks and devices so as to offer many new and innovative services to users in ubiquitous computing. For example, when you carry your mobile laptop or personal digital assistant (PDA) around, or drive on the road, various services have been made available, ranging from finding a local printer to print a file, to instantaneously knowing about the traffic situation from traffic-cameras and other sensors along a highway.
Key Terms in this Chapter
Service Advertisement: Is responsible for advertising a given service description on a directory service or directly to other hosts in the network. The effectiveness of an advertisement is measured as a combination of the extent of its outreach and the specificity of information it provides up front about a service (Sen, 2005).
Service Description: Is responsible for describing a service and the type of context information in a comprehensive, unambiguous manner that is machine interpretable to facilitate automation and human readable to facilitate rapid formulation by users (Sen, 2005).
Context: Any information that can be used to characterize the situation of an entity. An entity is a person, place, or object that is considered relevant to the interaction between a user and an application, including the user and the application themselves (Dey, 2001).
Service discovery: Is the keystone and carries out three main functions. It formulates a request, which is a description of the needs of a service consumer. This request is formatted in a similar manner to the service description. It also provides a matching function that pairs requests to services with similar descriptions, so that the service which can best fulfill service consumer’s needs on peer devices is selected. Finally, it provides a mechanism for the service consumer to communicate with the service provider (Sen, 2005).
Context-Awareness: To use context to provide relevant services to the user, where relevancy depends on the user’s task (Dey, 2000).A service is a component or application that performs the work on behalf of a requesting application or client (Intel).
Service Invocation: Is responsible for facilitating the use of a service. Its functions include transmitting commands from the service consumer to the service provider and receiving results. It is also responsible for maintaining the connection between the consumer and the provider for the duration of their interaction. A good invocation mechanism abstracts communication details from the service consumer and, in the case of network failure, redirects requests to another provider or gracefully terminates (Sen, 2005).
Client: An application that is interested in or requires some other application to perform some type of work for the client (Intel).
Ubiquitous Computing (ubicomp, or sometimes ubiqcomp): Integrates computation into the environment, and enables people to move around and interact with information and computing naturally and casually. One of the goals of ubiquitous computing is to enable devices to sense changes in their environment and to automatically adapt and act based on these changes according to user needs and preferences.