logic, and library and information science. Most fundamentally, however, it is studied

in epistemology. Different theories of knowledge have different implications for what is considered

relevant and these fundamental views have implications for all other fields as well.

Definition "Something is relevant to a task if it increases

the likelihood of accomplishing the goal, which is implied by T.".

A thing might be relevant, a document or a piece of information may be relevant. The

basic understanding of relevance does not depend on whether we speak of "things" or

"information". Epistemology

If you believe that schizophrenia is caused by bad communication between mother and child,

then family interaction studies become relevant. If, on the other hand, you subscribe to a

genetic theory of relevance then the study of genes becomes relevant. If you subscribe

to the epistemology of empiricism, then only intersubjectively controlled observations

are relevant. If, on the other hand, you subscribe to feminist epistemology, then the sex of

the observer becomes relevant. Epistemology is not just one domain among

others. Epistemological views are always at play in any domain. Those views determine

or influence what is regarded relevant. Relevance logic

In formal reasoning, relevance has proved an important but elusive concept. It is important

because the solution of any problem requires the prior identification of the relevant elements

from which a solution can be constructed. It is elusive, because the meaning of relevance

appears to be difficult or impossible to capture within conventional logical systems. The obvious

suggestion that q is relevant to p if q is implied by p breaks down because under standard

definitions of material implication, a false proposition implies all other propositions.

However though 'iron is a metal' may be implied by 'cats lay eggs' it doesn't seem to be relevant

to it the way in which 'cats are mammals' and 'mammals give birth to living young' are

relevant to each other. If one states "I love ice cream," and another person responds "I

have a friend named Brad Cook," then these statements are not relevant. However, if one

states "I love ice cream," and another person responds "I have a friend named Brad Cook

who also likes ice cream," this statement now becomes relevant because it relates to

the first person's idea. More recently a number of theorists have sought

to account for relevance in terms of "possible world logics" in intensional logic. Roughly,

the idea is that necessary truths are true in all possible worlds, contradictions are

true in no possible worlds, and contingent propositions can be ordered in terms of the

number of possible worlds in which they are true. Relevance is argued to depend upon the

"remoteness relationship" between an actual world in which relevance is being evaluated

and the set of possible worlds within which it is true.

Application Politics

During the 1960s, relevance became a fashionable buzzword, meaning roughly 'relevance to social

concerns', such as racial equality, poverty, social justice, world hunger, world economic

development, and so on. The implication was that some subjects, e.g., the study of medieval

poetry and the practice of corporate law, were not worthwhile because they did not address

pressing social issues. Economics

The economist John Maynard Keynes saw the importance of defining relevance to the problem

of calculating risk in economic decision-making. He suggested that the relevance of a piece

of evidence, such as a true proposition, should be defined in terms of the changes it produces

of estimations of the probability of future events. Specifically, Keynes proposed that

new evidence e is irrelevant to a proposition, given old evidence q, if and only if p/q & e

= p/q and relevant otherwise. There are technical problems with this definition,

for example, the relevance of a piece of evidence can be sensitive to the order in which other

pieces of evidence are received. Cognitive science and pragmatics

In 1986, Dan Sperber and Deirdre Wilson drew attention to the central importance of relevance

decisions in reasoning and communication. They proposed an account of the process of

inferring relevant information from any given utterance. To do this work, they used what

they called the "Principle of Relevance": namely, the position that any utterance addressed

to someone automatically conveys the presumption of its own optimal relevance. The central

idea of Sperber and Wilson's theory is that all utterances are encountered in some context,

and the correct interpretation of a particular utterance is the one that allows most new

implications to be made in that context on the basis of the least amount of information

necessary to convey it. For Sperber and Wilson, relevance is conceived as relative or subjective,

as it depends upon the state of knowledge of a hearer when they encounter an utterance.

Sperber and Wilson stress that this theory is not intended to account for every intuitive

application of the English word "relevance". Relevance, as a technical term, is restricted

to relationships between utterances and interpretations, and so the theory cannot account for intuitions

such as the one that relevance relationships obtain in problems involving physical objects.

If a plumber needs to fix a leaky faucet, for example, some objects and tools are relevant

and others are not. And, moreover, the latter seems to be irrelevant in a manner which does

not depend upon the plumber's knowledge, or the utterances used to describe the problem.

A theory of relevance that seems to be more readily applicable to such instances of physical

problem solving has been suggested by Gorayska and Lindsay in a series of articles published

during the 1990s. The key feature of their theory is the idea that relevance is goal-dependent.

An item is relevant to a goal if and only if it can be an essential element of some

plan capable of achieving the desired goal. This theory embraces both propositional reasoning

and the problem-solving activities of people such as plumbers, and defines relevance in

such a way that what is relevant is determined by the real world rather than the state of

knowledge or belief of a particular problem solver.

Law

The meaning of "relevance" in U.S. law is reflected in Rule 401 of the Federal Rules

of Evidence. That rule defines relevance as "having any tendency to make the existence

of any fact that is of consequence to the determinations of the action more probable

or less probable than it would be without the evidence." In other words, if a fact were

to have no bearing on the truth or falsity of a conclusion, it would be legally irrelevant.

Library and information science

This field has considered when documents retrieved from databases are relevant or non-relevant.

Given a conception of relevance, two measures have been applied: Precision and recall:

Recall = a : X 100%, where a = number of retrieved, relevant documents, c = number

of non-retrieved, relevant documents. Recall is thus an expression of how exhaustive a

search for documents is. Precision = a : X 100%, where a = number

of retrieved, relevant documents, b = number of retrieved, non-relevant documents.

Precision is thus a measure of the amount of noise in document-retrieval.

Relevance itself has in the literature often been based on what is termed "the system's

view" and "the user's view". Hjørland criticize these two views and defends a "subject knowledge

view of relevance". See also

Source criticism Description

Distraction Information-action ratio

Information overload Intention

Relevance theory References

Gorayska B. & R. O. Lindsay. The Roots of Relevance. Journal of Pragmatics 19, 301–323.

Los Alamitos: IEEE Computer Society Press. Hjørland, Birger. The foundation of the concept

of relevance. Journal of the American Society for Information Science and Technology, 61(2), 217-237.

Keynes, J. M.. Treatise on Probability. London: MacMillan

Lindsay, R. & Gorayska, B. Relevance, Goals and Cognitive Technology. International Journal

of Cognitive Technology, 1,, 187–232 Sperber, D. & D. Wilson Relevance: Communication

and Cognition. 2nd edition. Oxford: Blackwell. Sperber, D. & D. Wilson. Précis of Relevance:

Communication and Cognition. Behavioral and Brain Science, 10, 697–754.

Sperber, D. & D. Wilson. Relevance Theory. In Horn, L.R. & Ward, G. 2004 The Handbook

of Pragmatics. Oxford: Blackwell, 607-632. http:www.dan.sperber.fr/?p=93

Zhang, X, H.. A Goal-Based Relevance Model and its Application to Intelligent Systems.

Ph.D. Thesis, Oxford Brookes University, Department of Mathematics and Computer Science, October,

1993. External links

Malcolm Gladwell - Blink - full show: TVOntario interview regarding "snap judgements" and

Blink