  Context is a rich concept and is an elusive concept to define. The concept of
context has been studied by philosophers, linguists, psychologists, and
recently by computer scientists. Within each research community the term
context was interpreted in a certain way that is well-suited for their goals,
however no attempt was made to define context. In many areas of research in
computer science, notably on web-based services, human-computer interaction
(HCI), ubiquitous computing applications, and context-aware systems there is a
need to provide a formal operational definition of context. In this brief
survey an account of the early work on context, as well as the recent work on
many working definitions of context, context modeling, and a formalization of
context are given. An attempt is made to unify the different context models
within the formalization. A brief commentary on the usefulness of the
formalization in the development of context-aware and dependable systems is
included.
