Context-Aware Applications - Guide to Cloud Computing for Business and Technology Managers - page 508

23.2 Context-Aware Applications
Context is understood as “the location and identities of nearby people and
objects, and changes to those objects.” Initially, the term context was equivalent
to the location and identity of users and objects. Very soon, though, the term
expanded to include a more refined view of the environment assuming either
three major components—computing, user, and physical environment—or
four major dimensions, system, infrastructure, domain, and physical context.
The interaction between the user and application was added by Dey (2001)*;
according to them, a context is “any information that can be used to character-
ize the situation of an entity.” An entity should be treated as anything relevant
to the interaction between a user and an application, such as a person, a place,
or an object, including the user and the application themselves and, by exten-
sion, the environment the user and applications are embedded in. Thus, a sys-
tem is context-aware if it uses context to provide relevant information and/or
services to the user, where relevancy depends on the user's task.
An ontology is a formal, explicit specification of a shared conceptualization,
that is, an abstract model of some phenomenon in the world that identifies the
relevant concepts of that phenomenon ( explicit means that the type of concepts
used and the constraints on their use are explicitly defined, and formal refers to
the fact that the ontology should be machine readable). Given that ontologies
are a promising instrument to specify concepts and their interrelations, they
can provide a uniform way for specifying a context model's core concepts
as well as an arbitrary amount of subconcepts and facts, altogether enabling
contextual knowledge sharing and reuse in a ubicomp system. Ontologies are
developed to provide a machine-processable semantics of information sources
that can be communicated between different agents (software and humans). It
is a necessity to decouple the process of context acquisition and interpretation
from its actual use, by introducing a consistent, reliable, and secure context
framework that can facilitate the development of context-aware applications.
Context-aware features include using context to
1. Present information and services to a user
2. Automatically execute a service for a user
3. Tag information to support later retrieval
In supporting these features, context-aware applications can utilize numer-
ous different kinds of information sources. Often, this information comes
from sensors, whether they are software sensors detecting information about
the networked, or virtual, world or hardware sensors detecting information
about the physical world. Sensor data can be used to recognize the usage
* Dey, A.K. Understanding and using context. Personal and Ubiquitous Computing Journal , (1),
4 - 7, 2 0 0 1 .