A Brief History of Context

33 A Brief History of Context Kaiyu Wan

Computer Science Department, East China Normal University Shanghai, 200, China

Abstract 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.

Keywords: Context, Context Theory, Context-Awareness.

1. Introduction According to the Oxford English Dictionary (OED), context denotes “the circumstances that form the setting for an event”. To emphasize a common social usage of the word context OED includes the quotation [12] “I wish honorable gentlemen would have the fairness of what I did say, and not pick out detached words”. Although the word context has been used for a long time in many scientific descriptions, literary essays, and in philosophical discourses, its meaning was always left to the reader’s understanding. In one of the earlier papers, Clark and Carlson [11] state that Context has become a favorite word in the vocabulary of cognitive psychologists and that it has appeared in the titles of a vast number of articles. They then complain that the denotation of the word has become murkier as its uses have been extended in many directions and deliver the now widespread opinion that context has become some sort of “conceptual garbage can”. That context has changed now. The importance of context in information retrieval, knowledge representation, reasoning in AI, and analysis of computer programs have been recognized and there is a serious effort to make a precise technical working definition of the notion of context. More recently, the importance of context was picked up by researchers in many areas of computer science, most importantly those working in Human-Computer Interaction (HCI), semantic web, and trustworthy systems. This intense interest has produced many operational definitions of context, but almost all of them are either informal or use ad hoc notation. We review in this paper the different types of notations and interpretations used for context. The review is classified into Context in Logic, Context in Languages, and Context in Systems. This classification and review are not exhaustive. It is used mainly to trace the historical progression of the systematic study of context in different, but related, areas. 1.1 Structure and Interpretation The word “context” is derived from the Latin words con (meaning “together”) and texere (meaning “to weave”). The raw meaning of it is therefore “weaving together”. A circumstance is a weaving together of many types of entities. Thus, in describing a context we must define a finite set of entities, a finite set of properties for each entity, and the inter-weaving of the properties. As an example, the setting for a “seminar event” is the weaving together of the entities speaker, topic, audience, time, location and their properties such as name and affiliation for the speaker, title and abstract for the topic, size and status for audience, clocktime for time, and building- address and room-number for locality. We need to associate with each property a value from its domain and bind each entity with the instantiated properties in order to describe the context of seminar. The choice of entities, the choice of properties, and the notation used for binding them are crucial for system development. This choice for context definition has the effect of narrowing down the possible interpretations of declared policies and constraints for system development. Context description also eliminates ambiguities. It should be possible to define contexts in programming languages independent of how it IJCSI International Journal of Computer Science Issues, Vol. 6, No. 2, 2009

34 should be used. For example, if a context is defined by locality and time, then many events may happen in a specific context, and each event may produce a different experience in one context. Therefore, the

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