A class is - according to classical theory (Aristotle) - a collection of entities or elements sharing a
common attribute or property. The process of assigning elements to classes is
According to classical theory are all members of a class
sharing some necessary and sufficient properties, which define membership of the
class. According to the idea of ‘family resemblance’ (Wittgenstein) is this not
necessarily the case. A family resemblance is a vague grouping of things that
are together because of their similarities, but have no one thing in common. The
example Wittgenstein uses is that of games; all games do not have one underlying
trait in common, but are grouped together under the heading ‘games’.
"There is, in any case, a
difference in how we talk about types and kinds versus
how we talk about classes. We say that Socrates is a token of a
type, or an instance of the natural kind, human being.
But notice that we say instead that Socrates is a member
of the class of human beings. We would not say that Socrates is
a "member" of the type or kind, human beings. Nor would we say
he is a type (or kind) of a class. He is a token (instance) of
the type (kind). So the linguistic difference is: types (or
kinds) have tokens (or instances); classes, on the other hand,
have members." (Wikipedia, 2006c).
The prefix super-
indicates a rank above, the prefix sub- indicates a rank
below. In biology
the prefix infra- indicates a rank below sub-. For
The concept of "class" is related to the concept of
"concept": A concept defines a category or class of individuals. For example,
the concept [animal] defines the classes of entities such as cats, dogs, fish,
In a classification system like
Classification may a class (e.g., 780 Music) be expressed by a notation and
by a verbal phrase. It may also be described by a note indicating the definition of
the class, what to be included and what to be excluded. Such a note corresponds
to the intensional definition of a concept (what one must know in order to
identify the referent of the concept, i.e., the entities which belong to the
class). By enumerating a list of all concepts classified in the particular class
is given an extensional definition of that class. Some library
classifications, such as DK5 provide
special indexes enumerating all concepts identified with a given class. An
alternative is to retrieve a set of documents classified by a given class and
look at the terms used in the titles of the classified documents. This method is
often used of classifiers in order to decide where to classify a document.
Concepts and classes are defined or used on the basis of
some conceptualization of the domain, which is being classified. The most
important issue in classification is the the rationale behind given definitions
and conceptualizations of classes.
Wikipedia, the free encyclopedia. (2006a).
Class. Disambiguation page.
Wikipedia, the free encyclopedia. (2006b). Class (Computer science).
Wikipedia, the free encyclopedia. (2006c).
Wikipedia, the free encyclopedia. (2006d).
Class (set theory).
Concept in Knowledge Organization;