Definitions of general terms

Definitions for the WebKB set of tools

We mostly agree with the definitions presented in the Free On-line Dictionary of Computing (see below) except that we use the word "information" in a broader sense, i.e. as a synonym of "data". In the WebKB documentation, we also use hypertext terms in their usual sense (cf. W3C glossary).


Synonym of data. Information includes Document elements and knowledge.

Document element (DE)

Any textual/HTML data, e.g. a sentence, a section, a reference to an image or to a whole document. This excludes binary data but includes knowledge. Such information doesn't have to be extracted from a document; for example, it may be directed stored by a user in our warehouse.


Information represented with a knowledge representation language (KRL) so that a software may efficiently retrieve this information or use it for logical inferences.

Information retrieval (IR)

Retrieval of data, DEs or knowledge by queries or navigation.
Knowledge retrieval is knowledge-based IR, i.e. the exploitation of conceptual relations between pieces of information for retrieving them. In knowledge-based queries, logical inferences are automatically done. In knowledge-based navigation, the user is guided by the conceptual structuration of the displayed information.

Knowledge acquisition (KA)

The process of developing a knowledge-based system (KBS).
The output of KA doesn't have to be an operational KBS; it may just be a knowledge base (KB), e.g. an organised corporate memory. In that case, it is generally called knowledge modelling.
The development of a KBS is generally done using a "KA tool" (KAT) and following a methodology, e.g.the KADS methodology. The development, maintenance and exploitation of a KB may be done via a "KB management system" (KBMS), e.g. the WebKB set of tools or KMS. KATs are generally also KBMSs.

Related definitions from the Free On-line Dictionary of Computing


<domain: data processing> (Or "raw data", "information", "wisdom") Numbers, characters, images or other method of recording, in a form which can be assessed by a human or (especially) input into a computer, stored and processed there, or transmitted on some digital channel.

Data on its own has no meaning, only when interpreted by some kind of data processing system does it take on meaning and become information. For example, the number 123454657.99 is data but if it is output as your bank balance then that is information.

People or computers can find patterns in data to perceive information, and information can be used to enhance knowledge. Since knowledge is prerequisite to wisdom, we always want more data and information. But, as modern societies verge on information overload, we especially need better ways to find patterns.

123454657.99 is data.
"Your bank balance has jumped 8087% to 123454657.99" is information.
"Nobody owes me that much money" is knowledge.
"I'd better talk to the bank before I spend it, because of what has happened to other people" is wisdom.

Data processing

<domain: application> The input, verification, organisation, storage, retrieval, transformation, and extraction of information from data. The term is normally associated with commercial applications such as stock control or payroll.


<domain: artificial intelligence> The objects, concepts and relationships that are assumed to exist in some area of interest. A collection of knowledge, represented using some knowledge representation language is known as a knowledge base and a program for extending and/or querying a knowledge base is a knowledge-based system.

Knowledge differs from data or information in that new knowledge may be created from existing knowledge using logical inference. If information is data plus meaning then knowledge is information plus processing.

A common form of knowledge, e.g. in a Prolog program, is a collection of facts and rules about some subject.

For example, a knowledge base about a family might contain the facts that John is David's son and Tom is John's son and the rule that the son of someone's son is their grandson. From this knowledge it could infer the new fact that Tom is David's grandson.

Knowledge representation

<domain: artificial intelligence> The subfield of artificial intelligence concerned with designing and using systems for storing knowledge - facts and rules about some subject.

A body of formally represented knowledge is based on a conceptualisation - an abstract view of the world that we wish to represent. In order to manipulate this knowledge we must specify how the abstract conceptualisation is represented as a concrete data structure. An ontology is an explicit specification of a conceptualisation.

Knowledge base (KB)

<domain: artificial intelligence> A collection of knowledge expressed using some formal knowledge representation language. A knowledge base forms part of a knowledge-based system (KBS).

Knowledge-based system (KBS)

<domain: artificial intelligence> A program for extending and/or querying a knowledge base.

The Cyc project is an example of a large KBS.

[Difference from "expert system"?]


1. <domain: philosophy> A systematic account of Existence.

2. <domain: artificial intelligence> (From philosophy) An explicit formal specification of how to represent the objects, concepts and other entities that are assumed to exist in some area of interest and the relationships that hold among them.

For AI systems, what "exists" is that which can be represented. When the knowledge about a domain is represented in a declarative language, the set of objects that can be represented is called the universe of discourse. We can describe the ontology of a program by defining a set of representational terms. Definitions associate the names of entities in the universe of discourse (e.g. classes, relations, functions or other objects) with human-readable text describing what the names mean, and formal axioms that constrain the interpretation and well-formed use of these terms. Formally, an ontology is the statement of a logical theory.

A set of agents that share the same ontology will be able to communicate about a domain of discourse without necessarily operating on a globally shared theory. We say that an agent commits to an ontology if its observable actions are consistent with the definitions in the ontology. The idea of ontological commitment is based on the Knowledge-Level perspective.

3. <domain: library> The hierarchical structuring of knowledge about things by subcategorising them according to their essential (or at least relevant and/or cognitive) qualities. See subject index. This is an extension of the previous senses of "ontology" (above) which has become common in discussions about the difficulty of maintaining subject indices.


<domain: logic> The logical process by which new facts are derived from known facts by the application of inference rules.

Dr. Philippe A. MARTIN

Last modified: Thu Sep 3 01:10:52 PDT 1998