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Classification and Categorization: A Difference that Makes a Difference


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Examination of the systemic properties and forms of interaction that characterize classification and categorization reveals fundamental syntactic differences between the structure of classification systems and the structure of categorization systems. These distinctions lead to meaningful differences in the contexts within which information can be apprehended and influence the semantic information available to the individual. Structural and semantic differences between classification and categorization are differences that make a difference in the information environment by influencing the functional activities of an information system and by contributing to its constitution as an information environment. published or submitted for publication
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LIBRARY TRENDS, Vol. 52, No. 3, Winter 2004, pp. 515–540
© 2004 The Board of Trustees, University of Illinois
Classification and Categorization:
A Difference that Makes a Difference
Elin K. Jacob
Examination of the systemic properties and forms of interaction
that characterize classification and categorization reveals fundamental syn-
tactic differences between the structure of classification systems and the
structure of categorization systems. These distinctions lead to meaningful
differences in the contexts within which information can be apprehended
and influence the semantic information available to the individual. Struc-
tural and semantic differences between classification and categorization are
differences that make a difference in the information environment by in-
fluencing the functional activities of an information system and by contrib-
uting to its constitution as an information environment.
Many different and sometimes conflicting responses can be made to the
question “What is information?” Floridi (in press) identifies three broad cat-
egories intended to elucidate the predominant approaches to understand-
ing the ambiguous phenomenon called information: information as reality
(or ecological information), information for reality (or instructional infor-
mation), and information about reality (or semantic information). The ap-
proach adopted here is that information is “differences that make a differ-
ence” (Bateson, 1979, p. 99). It is an emergent property—the result of
meaningful differences—inherently semantic and therefore about reality.
Analysis of the syntactic differences that distinguish systems of classifi-
cation from systems of categorization can contribute to a philosophy of
information (PI) because these distinctions portend significant conse-
quences for the processes that contribute to what Floridi (2002) describes
Elin K. Jacob, School of Library and Information Science, Indiana University–Bloomington,
1320 E. 10th St., Bloomington, IN 47405–1801
516 library trends/winter 2004
as the “dynamics of information”: “(i) the constitution and modelling of infor-
mation environments, including their systemic properties, forms of interac-
tion, internal developments etc.; (ii) information life cycles, i.e., the series of
various stages in form and functional activity through which information
can pass . . . and (iii) computation, both in the Turing-machine sense of al-
gorithmic processing and in the wider sense of information processing” (p. 15.
emphasis in original). Examination of the systemic properties and forms
of interaction that characterize classification and categorization reveals fun-
damental differences in their respective organizational structures—differ-
ences that influence the functional activities of an information system and
contribute to its constitution as an information environment.
The argument elaborated here is that fundamental syntactic distinc-
tions exist between the structure of classification systems and the structure
of categorization systems; that these distinctions lead to meaningful differ-
ences in the contexts within which information can be apprehended; and
that these differences, in turn, influence the semantic information—the
information about reality—that is available to the individual.
Information Systems
Shera (1960/1965) has observed that retrieval must be the focus of a
theory of library and information science (LIS) and thus “the end toward
which all our efforts are directed” (p. 136). Unfortunately, retrieval is too
often viewed not as one component in an information system but as a self-
contained and independent process. This emphasis on the end product—
the retrieval of resources—tends to obscure the fact that effective retrieval
depends on both the representation and the organization of a collection
of information resources.
Soergel (1985) points out that, because information is used for prob-
lem-solving, information systems are developed and extended in response
to the problems that confront society. Although this definition of informa-
tion is not universally accepted, it is useful in understanding the complex
set of processes that contribute to the ultimate effectiveness of an informa-
tion system. Such a system identifies information resources that may be of
use in addressing a particular problem; represents the attributes of re-
sources that are relevant to the problem area; organizes these resource rep-
resentations or the resources themselves for efficient access; and ultimate-
ly retrieves a set of resources in response to queries presented to the system
by the individual. It would appear, then, that a more productive approach
to the problem of retrieval would be to view an information system as a mul-
tidimensional whole comprised of several interrelated processes, including,
at a minimum, collection development, representation, organization, and
Retrieval is the final and therefore the most obvious of the processes
that contribute to an information system. Because it is the only process in
517jacob/classification and categorization
which an individual actively participates, it is frequently the only process
to which she gives serious consideration. When the individual is seeking
information on a particular topic, her attention is focused on the set of
resources retrieved by the information system. If these resources appear to
be pertinent to the immediate problem, she may not give a second thought
to the appropriateness of the terms used to query the information system.
Nonetheless, it is the processes of selection, representation, and organiza-
tion that provide the foundation without which information retrieval (IR)
is less than effective, if not impossible. How resources are represented con-
strains the organizational structure(s) that can be imposed on a collection
of information resources; the organizational structure of the collection
dictates the search strategies that can be used for retrieval; and the repre-
sentations themselves determine the set of resources that will be retrieved
by the system.
Shera (1956/1965) affirmed the critical roles of representation and or-
ganization when he observed that effective retrieval requires an accord be-
tween the cognitive organization imposed on information by the individu-
al and the formal organization imposed upon representations by the system.
Shera’s argument for accord between the individual and the retrieval sys-
tem rests on three basic assumptions: that there are certain cognitive struc-
tures that can be identified and described; that it can be demonstrated that
these structures are shared across individuals; and that identification of these
shared structures will provide the basis for a theory of organization.
That cognitive accord can be achieved across individuals is a fundamen-
tal assumption of the shareability constraint proposed by Freyd (1983). She
argued that the intent to communicate without loss of information causes
the individual to modify her internal conceptual representations to reflect
the cognitive organization assumed to be held by the other participant(s)
in the communicative process. If participation in an intentional act of com-
munication does promote normalization of conceptual representations
across individuals, as Freyd (1983) argues, it follows that an intentional act
of communication between the individual as natural intelligence and the
information system would be subject to a similar shareability constraint.
Assuming that the processes of representation, organization, and retrieval
are necessarily interdependent, failure to address communication between
the individual and the information system from the perspective of the sys-
tem is a significant omission. Thus, an accounting of the dynamics of in-
formation should address the role of representation and organization in
the creation and communication of meaningful information. More impor-
tantly, it should account for the semantic implications occasioned by dif-
ferences in the forms of organization that can be used to structure an in-
formation system.
The need for effective communication between the information system
and the individual points to five areas of research: (i) Is communication
518 library trends/winter 2004
between the information system and the individual influenced by the rep-
resentation of resources? (ii) Does the organizational structure of the in-
formation system cause the individual to adjust her internal cognitive struc-
tures? (iii) Does the organization of resources contribute to the creation
of a meaningful context for information? (iv) Is the meaning of informa-
tion influenced by the organizational structure of the information system?
and (v) What consequences follow from the different organizational struc-
tures that can be applied to a collection of information resources?
An understanding of the different forms of organizational structure and
the implications that each holds for creating a meaningful context for in-
formation is foundational and must therefore precede any discussion of the
role that representation and organization play in the dynamics of informa-
tion. Accordingly, the focus here is on the ramifications of organizational
structure for communication between the information system and the in-
dividual as natural intelligence. More specifically, the argument presented
here addresses the fundamental structural and semantic differences be-
tween classification and categorization and how these differences make a
difference in the information environment.
Categorization is the process of dividing the world into groups of enti-
ties whose members are in some way similar to each other. Recognition of
resemblance across entities and the subsequent aggregation of like entities
into categories lead the individual to discover order in a complex environ-
ment. Without the ability to group entities based on perceived similarities,
the individual’s experience of any one entity would be totally unique and
could not be extended to subsequent encounters with similar entities in the
environment. Consider a situation in which each separate entity—each tree,
each flower, or each drop of rain—was distinct from all other entities and
carried its own unique set of defining characteristics. As Markman (1989)
observes, the individual would not be able to handle the variety and com-
plexity of her day-to-day interactions with the environment. By reducing the
load on memory and facilitating the efficient storage and retrieval of infor-
mation, categorization serves as the fundamental cognitive mechanism that
simplifies the individual’s experience of the environment.
Categorization divides the world of experience into groups or catego-
ries whose members share some perceptible similarity within a given con-
text. That this context may vary and with it the composition of the catego-
ry is the very basis for both the flexibility and the power of cognitive
categorization. Zerubavel (1993) contends that the individual finds order
and meaning in the environment by imposing boundaries—by splitting and
lumping objects of experience so as to create distinct “islands of meaning”
(p. 5). How an entity is categorized creates a context or conceptual frame
that not only provides information about the entity but also shapes the in-
519jacob/classification and categorization
dividual’s interaction with it. For example, the historic period known as the
English Renaissance (1500–1650) is perceived as fundamentally different
from the English Middle Ages even though England in the sixteenth cen-
tury was, in many respects, quite similar to England in the fifteenth centu-
ry. Splitting the sixteenth century from the fifteenth century by labeling
them as belonging to two distinct historical periods focuses attention on
the differences between them rather than on their similarities and provides
the information that, in England, these differences were of greater import
than differences between the fourteenth and fifteenth centuries.
Barsalou (1987) points out that this ability to manipulate the environ-
ment through the creation of categories allows the individual to forge new
relationships and thus to create new information whose value exceeds the
simple grouping of objects in the environment. He proposes that, because
different features or properties are used to represent the same category at
different times and in different contexts, the information associated with
a particular category varies across individuals and across contexts. Thus the
set of features associated with a category on any given occasion is composed
of both context-dependent and context-independent information. Context-
dependent information is relevant only within a particular context. For
example, a high temperature of 50 degrees Fahrenheit might be described
as cold on a summer day in southern Indiana, but warm or even hot on a
winter day in the same locale. To say that it is cold outside conveys context-
dependent information that is meaningful only in relation to the seasonal
context. In contrast, context-independent information provides informa-
tion about a category that is relevant across contexts. Even when used met-
aphorically, for example, the word “fire” connotes heat, light, and energy.
The apparent instability of categories is therefore a reflection of the flexi-
bility and the plasticity that are the power of the cognitive process of cate-
gorization and of the individual’s ability to create and modify the informa-
tional content of a category as a function of immediate context, personal
goals, or past experience.
The acquisition and transmission of information are dependent not
only on the cognitive ability to create new categories—and thus new infor-
mation—through the discovery of new patterns of similarity across entities,
but also on the ability to capture information about these patterns through
the medium of language. With the accumulation of more specialized knowl-
edge and the creation of disciplinary domains, however, these categories
and the relations between them have a tendency to become formalized
(Jacob, 1994). The need to ensure that disciplinary knowledge is consis-
tent across individuals and across time privileges the stability of reference
provided by well-defined classes. As experientially-based categories evolve
into well-defined, domain-specific classes that facilitate sharing of knowl-
edge without loss of information, they lose their original flexibility and
plasticity as well as the ability to respond to new patterns of similarity.
520 library trends/winter 2004
The Classical Theory of Categories
Until Rosch’s publication in the 1970s of her seminal work on catego-
ries and categorization (Rosch, 1973, 1975), research in the area of cate-
gorization had focused on concept formation not as a process of creation
but as a process of recognition. The world of experience was assumed to
consist of a set of predetermined categories, each defined by a set of essen-
tial features represented by a category label; and all members of a given
category were assumed to share a set of essential features that was identified
by the category label and could be apprehended by all members of the lin-
guistic community. Thus Hull (1920) wrote of the child’s discovery of mean-
ing in the word “dog” as the gradual recognition of a preexisting and in-
variant concept: “The ‘dog’ experiences appear at irregular intervals. . . .
At length the time arrives when the child has a ‘meaning’ for the word dog.
Upon examination this meaning is found to be actually a characteristic
more or less common to all dogs and not common to cats, dolls and ‘ted-
dy-bears’” (Hull, 1920, pp. 5–6; cited in Brown, 1979, p. 188).
The presumption that a category is determined by a set of defining
criteria is known as the “classical theory of categories.” This is a simple but
powerful theory that rests on three basic propositions (Smith & Medin,
1981; see also Taylor, 1989):
1. The intension of a category is a summary representation of an entire
category of entities.
2. The essential features that comprise the intension of a category are in-
dividually necessary and jointly sufficient to determine membership
within the category.
3. If a category (A) is nested within the superordinate category (B), the
features that define category (B) are contained within the set of features
that define category (A).
Proposition I states that the definition (intension) of a category is the
union of the essential features that identify the membership (extension) of
that category. Furthermore, because all members of a single category must
share this set of essential features, each member is equally representative
of the category as a whole. For this reason, the internal structure of a cate-
gory is said to be ungraded, or without rank, because no member can be
more typical or more representative of a category than any other member.
Proposition II states that, because each member of the category must
exhibit all of the essential features that comprise the intension of the cate-
gory, possession of the set of features that defines the category is sufficient
to determine membership in the category. And, because there is a binary,
either/or relationship that exists between an entity and a category such that
an entity either is or is not a member of a particular category, the bound-
aries of categories are said to be fixed and rigid.
Proposition III identifies the inheritance relationship that exists be-
521jacob/classification and categorization
tween categories in a hierarchical structure: any member of a category that
is a subset of a superordinate category must exhibit not only the set of es-
sential features that determine membership in the subset but also the set
of essential features that determine membership in any superordinate cat-
egory within which the subset is nested.
In its most rudimentary form, categorization can be defined as the
placement of entities in groups whose members bear some similarity to each
other. Within the framework of the classical theory of categories, however,
categorization is the process of systematically dividing up the world of ex-
perience into a formalized and potentially hierarchical structure of cate-
gories, each of which is defined by a unique set of essential feature(s).
Because the intension of a category defines the set of essential features that
each member of the category must exhibit, the classical theory maintains
that intension equals extension—that membership within a particular cat-
egory (extension) entails possession of the essential and defining charac-
ter (intension) of the category. For example, if the intension of the cate-
gory “bird” consists of the features “lays eggs,” “has wings,” “flies,” and
“builds nests in high places,” every member of the category must exempli-
fy the complete set of defining features. If an entity does not fly, it cannot
be accorded membership in the category “bird” even if it does lay eggs, have
wings, and build nests in high places. And, because all members of the cat-
egory are defined by the same set of features, no one bird can be more typ-
ical or more representative of the category than any other bird. Thus, ac-
cording to the classical theory, a parrot, a pigeon, and a puffin would be
equally representative of the category “bird.”
Brown (1979) observes that within the formalized and rigidly con-
strained ordering of reality established by the classical theory, category
membership is absolute: “. . . any given thing is either in or out of the set”
(p. 189). It is this stipulation that is the source of the classical theory’s ex-
planatory power: because it requires that intension equals extension—that
membership in a category demonstrates possession of the set of essential
features that define the category—the classical theory of categories would
provide a simple yet elegant explanation for both the internal structure of
cognitive representations and the semantic meanings of words.
Until recently, the classical theory of categories exemplified “the ‘right
way’ to think about categories, concepts, and classifications” (Gardner, 1987,
p. 340). But empirical research conducted over the past thirty years has
challenged the validity of the assumptions on which this theory is found-
ed. Critics of the classical theory have argued that the inability of subjects
to identify the defining characteristics of an entity (Hampton, 1979; Rosch
& Mervis, 1975) not only undermines the assumption that the set of essen-
tial features determining category membership is absolute but also calls into
question the notion that these features are available to and can be specified
by all members of a linguistic community. Demonstration of graded typi-
522 library trends/winter 2004
cality effects—the observation that subjects do judge certain members to
be more representative of a category than others (McCloskey & Glucksberg,
1978; Rips, Shoben, & Smith, 1973; Rosch, 1973, 1975)—controverts the
assumption that category structure is ungraded because all members are
equally representative of the category. There is evidence, too, that subjects
are able to rank both members and nonmembers of a category on a single
continuum of representativeness. For example, Barsalou (1987) demon-
strated that subjects could rank a robin, a pigeon, an ostrich, a butterfly,
and a chair on a single continuum of representativeness for the category
“bird”—a continuum extending from the most typical member of the cat-
egory (robin) to the most atypical member (chair). The evidence for graded
structure of categories points to the lack of fixed and determinate bound-
aries separating members of a category from nonmembers; and, buttressed
as it is by demonstrations of category membership based on family resem-
blance (Rosch & Mervis, 1975), graded structure casts doubt on the classi-
cal assumption that there is an explicit inclusion/exclusion relationship
between an entity and a category.
In LIS, the term “classification” is used to refer to three distinct but
related concepts: a system of classes, ordered according to a predetermined
set of principles and used to organize a set of entities; a group or class in a
classification system; and the process of assigning entities to classes in a
classification system. The focus here is on the first of these—on the classifi-
cation system as a representational tool used to organize a collection of
information resources—but a full appreciation of the implications of
classification for information environments requires a basic understanding
of the classification process itself.
Classification as process involves the orderly and systematic assignment
of each entity to one and only one class within a system of mutually exclu-
sive and nonoverlapping classes. This process is lawful and systematic: law-
ful because it is carried out in accordance with an established set of princi-
ples that governs the structure of classes and class relationships; and
systematic because it mandates consistent application of these principles
within the framework of a prescribed ordering of reality. The scheme itself
is artificial and arbitrary: artificial because it is a tool created for the express
purpose of establishing a meaningful organization; and arbitrary because
the criteria used to define classes in the scheme reflect a single perspective
of the domain to the exclusion of all other perspectives.
Taxonomic Classification.
Classification is perhaps best exemplified by the discipline of taxono-
my. Broadly defined, taxonomy is the science of classification or, as Mayr
(1982) defines it, “the theory and practice of delimiting kinds of organisms”
523jacob/classification and categorization
(p. 146). The objectives of taxonomic investigation are to provide an or-
derly and systematic organization of knowledge about the biological world;
to identify the defining characteristics that distinguish a biological entity;
and, based on those characteristics, to place the entity within a hierarchi-
cal ordering of mutually exclusive superordinate and subordinate classes
in accordance with a set of established and widely accepted principles.
Taxonomic classification establishes stability of nomenclature through
the aegis of a formalized and universally accepted language that facilitates
transmission of knowledge across time and the barriers of natural language.
Each class in the taxonomic scheme is given a unique name that is used to
refer to all entities that display the complete set of features defining the
class. And, because it is universally employed to identify all members of a
given class, this label provides access to the accumulated knowledge about
those entities, not as individuals but as members of a particular class. The
taxonomic name establishes a relationship of equivalence between the set
of features that define the class (its intension) and the set of entities that
are members of the class (its extension). Using the taxonomic name, a
member of a biological class is recognizable wherever it occurs, regardless
of natural language or the local name(s) by which it may be known.
Through the inheritance of definitional criteria made possible by en-
forcing a principled structure of superordinate and subordinate classes,
taxonomic classification also serves as an external cognitive scaffolding
(Clark, 1997; Jacob 2001, 2002) that provides for the economical storage
and retrieval of information about a class of entities. For example, the ob-
servation that Bleu is a poodle provides information about Bleu that is as-
sociated with the class “poodle.” More importantly, however, it also provides
information about Bleu that is available from the hierarchical structure
within which the class “poodle” is nested—information associated with the
superordinate classes dog, mammal, vertebrate, etc.
The essential observation, however, is that the practice of taxonomy is
carried out within the arbitrary framework established by a set of universal
principles. For example, while the naturalist Adanson, a contemporary of
Linneaus, proposed a method for organizing botanical phenomena based
on the identification of differences between individual specimens (Foucault,
1970), Linneaus advocated a systematic approach based on similarity of re-
productive structure. For the naturalist following Linneaus’s lead, any phys-
ical differences between two specimens not directly related to the process
of reproduction would be irrelevant: for example, differences of leaf, stem,
or root structure that might be used to distinguish between two plants would
be ignored if the plants exhibited similar reproductive structures.
Taxonomic classification supports the efficient storage and retrieval of
information about a class of entities, but reliance on a systematic approach
such as that advocated by Linneaus constrains the information context by
limiting the identification of knowledge-bearing associations to hierarchi-
524 library trends/winter 2004
cal relationships between classes. Furthermore, class definitions based on
a single feature such as reproductive structure effectively reduce the amount
of meaningful information that can be represented about each class in the
Classification Schemes.
A classification scheme is a set of mutually exclusive and nonoverlap-
ping classes arranged within a hierarchical structure and reflecting a pre-
determined ordering of reality. Because a classification scheme mandates
that an entity can be a member of one and only one class, it provides for
communication of meaningful information through the systematic and
principled ordering of classes. Furthermore, it establishes and enforces
stability of reference by providing each class with a unique label that links
individual members of the class to the class definition.
Shera (1951/1965) observes that, throughout history, attempts to clas-
sify knowledge have relied on four basic assumptions: universal order, uni-
ty of knowledge, similarity of class members, and intrinsic essence. The
assumption of universal order posits an immutable conception of reality that
serves as a unifying framework for all knowledge. The assumption of unity
of knowledge presupposes that past, present, and future knowledge can be
represented within a single, inclusive hierarchy of superordinate and sub-
ordinate classes. The assumption of similarity of class members holds that
a class can be defined by a set of essential features and that these features
are shared by all members of the class and distinguish that class from all
other classes in the structure. And the assumption of intrinsic essence
maintains that there is a set of individually necessary and jointly sufficient
features that is intrinsic to all members of a class and that these features
constitute the essence of the class.
With the possible exception of universal order, Shera’s exposition of
the assumptions that support efforts to organize knowledge can be inter-
preted in terms of the three propositions that constitute the classical theo-
ry of categories: the assertion that a category is defined by a summary rep-
resentation (Proposition I) is a statement of the essential similarity of class
members; the assertion that a category is defined by a set of essential fea-
tures (Proposition II) is a statement of the intrinsic essence of a class; and
the assertion that defining features are inherited in a hierarchical structure
of categories (Proposition III) is a statement of the unity of all knowledge.
It is instructive that, although the classical theory of categories is unable to
account for the variability and flexibility of cognitive categorization, it does
provide an elegant accounting of the fundamental assumptions on which
classification schemes have historically been constructed.
Bibliographic Classification Schemes.
Traditionally, bibliographic classifications have been deductive, top-
down schemes that enumerate a set of mutually exclusive classes. An enu-
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merative classification scheme begins with a universe of knowledge and a
theory of organization or set of principles that establishes the conceptual
structure of the scheme. Whether the universe encompasses all knowledge
or is limited to a specific domain, construction of the scheme involves the
logical process of division and subdivision of the original universe such that
each class, or each level of classes in the structure, is differentiated by a
particular characteristic or property (e.g., the property “color” or “shape”).
The result is a hierarchical structure of generic (genus/species) relation-
ships wherein each subordinate class is, theoretically, a true species of the
superordinate within which it is nested.
Faceted (analytico-synthetic) classification systems are inductive, bot-
tom-up schemes generated through a process of analysis and synthesis.
Construction of the faceted structure begins with analysis of a universe of
knowledge to identify the individual elements—properties and features—
of the universe. These elements are then organized into mutually exclusive
groups on the basis of conceptual similarity, and these groups are, in turn,
arranged in successively larger groupings to form facets (aspects) that can
be used to represent entities in the universe. In this way, meaningful rela-
tionships are established not only between the elements in a group but
between the groups themselves. The result is not a classification scheme but
a controlled vocabulary of concepts and their associated labels that can be
used, in association with a notation and a prescribed citation order, to syn-
thesize the classes that will populate the classification scheme. A faceted
vocabulary for classifying cars might include mutually exclusive facets for
“color” (red, blue, black), “body style” (sedan, convertible, minivan), and
“transmission” (manual, automatic). Following the citation order body style
transmissioncolor, classes would be constructed by selecting a single value,
or isolate, from each facet. Examples of the classes that could be constructed
in this faceted scheme would be convertible—manual—red and minivan—
Because a faceted classification scheme adheres to a fixed citation or-
der during the construction of individual classes, the resulting structure,
like an enumerative scheme, is necessarily hierarchical. In fact, it is the
hierarchical nature of bibliographic classification schemes that allows for
the arrangement of physical resources on the shelves of the library. “Read-
ing” a classification scheme involves moving down the hierarchy, from su-
perordinate to subordinate and from left to right, to generate a series of
relationships between classes that can be translated into the linear order
of the library shelf. It is just this linear structure that Ranganathan captured
in the notion of APUPA (or Alien-Penumbral-Umbral-Penumbral-Alien).
The umbral class (U) represents the focal topic; penumbral classes (P) are
those most closely related to the focal topic; and alien classes (A) are those
removed from and therefore unrelated to the focal topic. When the indi-
vidual reviews a collection of resources arranged in classified order, she
526 library trends/winter 2004
generally begins with the most relevant class or focal topic (U); moving
either to the right or the left, she progresses from resources on the focal
topic through closely related materials (P) to those resources which are
unrelated (A). In this fashion, the linearity inherent in the hierarchical
structure of a classification scheme is used to create a meaningful context
by bringing into proximity those classes within the hierarchical structure
which are theoretically most closely related.
Linearity is, in fact, the first of seven properties that Shera (1953/1965)
identifies as characteristic of a bibliographic classification scheme: lineari-
ty; inclusivity of all knowledge within the classification’s universe; well-
defined, specific, and meaningful class labels; an arrangement of classes that
establishes meaningful relationships between them; distinctions between
classes that are meaningful; a mutually exclusive and nonoverlapping class
structure; and an infinite hospitality that can accommodate every entity in
the bibliographic universe. Each of these properties contributes to Shera’s
definition of a bibliographic classification scheme as
a list of terms which are specifically and significantly different each from
the other, capable of describing the subject content of [resources],
inclusive of all knowledge, infinitely hospitable, in an arrangement that
is linear, unique, and meaningful, and which when applied to [re-
sources], usually, though not necessarily, through the medium of a
notation, results in their arrangement on the shelves according to the
logical principles that inhere in the schematism. (Shera, 1953/1965,
p. 99)
In other words, a bibliographic classification establishes a controlled vocab-
ulary in the form of a set of uniquely labeled classes that serve both to define
and to organize the intellectual content of a collection of resources. Fur-
thermore, this vocabulary determines the conceptual boundaries of the
scheme’s universe by including only the knowledge that is relevant within
the immediate universe. The resulting arrangement is meaningful precisely
because it constitutes a principled context for information—a context
shaped by class definitions, by information-bearing, hierarchical relation-
ships and by meaningful distinctions between classes and, by extension,
between the concepts that those classes represent.
Classification as a Disciplinary Language.
A classificatory structure frequently inheres in a disciplinary language
when it is used to establish a specific conceptual context that both defines
and organizes the domain of investigation (Foucault, 1970; Jacob, 1994).
The language serves to prescribe the boundaries of the domain; to deter-
mine both the subject matter of the domain and the relationships that
obtain between phenomena of investigation; to legitimize specific concepts
and methodologies; to ensure effective transmission of knowledge by sta-
bilizing the vocabulary; and to foster a domain-specific perspective or dis-
527jacob/classification and categorization
ciplinary episteme. Because a disciplinary language reflects the underlying
classificatory structure of the domain, the meaning of any class term can
only be apprehended within the conceptual context established by the
classificatory structure.
The Difference between Classification
and Categorization
Although there are obvious similarities between classification and cat-
egorization, the differences between them have significant implications for
the constitution of an information environment. Failure to distinguish
between these two systems of organization appears to stem from the mis-
conception that they are, in fact, synonymous—a misconception that may
be reinforced by the fact that both are mechanisms for organizing infor-
The literature on categorization is riddled with passages where the
terms “classification” and “categorization” are used indiscriminately to re-
fer to the same process. Rosch et al. (1976) provides an illustrative exam-
ple of how these two terms are used indiscriminately:
. . . one purpose of categorization is to reduce the infinite differences
among stimuli to behaviorally and cognitively usable proportions. It is
to the organism’s advantage not to differentiate one stimulus from
others when that differentiation is irrelevant for the purposes at hand.
The basic level of classification, the primary level at which cuts are made
in the environment, appears to result from the combination of these
two principles; the basic categorization is the most general and inclusive
level at which categories can delineate real-world correlational struc-
tures. (Rosch et al., 1976, p. 384. Emphasis added)
This lack of distinction between category/categorization and class/classification
is frequently compounded by the use of concept as yet another synonym for
category (e.g., Gardner, 1987, p. 340). Unfortunately, this terminological
imprecision obscures the fact that researchers are actually dealing with two
similar but nonetheless distinct approaches to organization.
Although systems of classification and categorization are both mecha-
nisms for establishing order through the grouping of related phenomena,
fundamental differences between them influence how that order is effect-
ed—differences that do make a difference in the information contexts es-
tablished by each of these systems. While traditional classification is rigor-
ous in that it mandates that an entity either is or is not a member of a
particular class, the process of categorization is flexible and creative and
draws nonbinding associations between entities—associations that are based
not on a set of predetermined principles but on the simple recognition of
similarities that exist across a set of entities. Classification divides a universe
of entities into an arbitrary system of mutually exclusive and nonoverlap-
ping classes that are arranged within the conceptual context established by
528 library trends/winter 2004
a set of established principles. The fact that neither the context nor the com-
position of these classes varies is the basis for the stability of reference pro-
vided by a system of classification. In contrast, categorization divides the
world of experience into groups or categories whose members bear some
immediate similarity within a given context. That this context may vary—
and with it the composition of the category—is the basis for both the flex-
ibility and the power of cognitive categorization ( Jacob, 1992).
Figure 1 identifies six systemic properties that serve as a starting point
for comparing systems of classification and categorization: (i) process, (ii)
boundaries, (iii) membership, (iv) criteria for assignment, (v) typicality, and
(vi) structure.
(i) The process of classification involves systematic arrangement of class-
es of entities based on analysis of the set of individually necessary and jointly
sufficient characteristics that defines each class. In contrast, the process of
categorization is generally unsystematic but inherently creative in that it
need not rely on predetermined definitions but is able to respond to sim-
ilarity assessments based on immediate context, personal goals, or individ-
ual experience.
Figure 1. Comparison of Categorization and Classification.
Categorization Classification
Creative synthesis of entities Systematic arrangement of entities
based on context or based on analysis of necessary and
perceived similarity sufficient characteristics
Because membership in any group Because classes are mutually-exclusive
is non-binding, and non-overlapping,
boundaries are “fuzzy” boundaries are fixed
Flexible: category membership is Rigorous: an entity either is or is not
based on generalized knowledge a member of a particular class
and/or immediate context based on the intension of a class
Criteria for Assignment
Criteria both context-dependent Criteria are predetermined
and context-independent guidelines or principles
Individual members All members are
can be rank-ordered by typicality equally representative
(graded structure) (ungraded structure)
Clusters of entities; Hierarchical structure
may form hierarchical structure of fixed classes
529jacob/classification and categorization
(ii) Systems of classification and categorization are also distinguished
by the boundaries imposed on groupings. Because the classes in a classifi-
cation system are rigidly circumscribed by the intension of the class and
further constrained by the requirement that they be mutually exclusive and
nonoverlapping, boundaries between classes are fixed, determinate, and
persistent. In a categorization system, however, membership of an entity in
any one category is nonbinding and does not prohibit membership in any
other category. Thus the membership of any two or more categories in a
system of categorization may overlap or vary across time in response to
changing contexts. This is possible because category boundaries are not
simply fuzzy but are, in fact, mutable and potentially fluid.
(iii) and (iv) Membership and criteria for assignment are two closely
related characteristics that distinguish systems of classification from systems
of categorization. In a classification system, criteria for class assignment—
the set of necessary and sufficient features that constitutes the intension of
a class—are governed by principles that establish the conceptual framework
of the system. Membership in a class is rigorous in that it is determined by
the intension of the class: an entity either is or is not a member of any class
in the system. More importantly, however, membership in a class is abso-
lute simply because an entity can belong to one and only one class. In con-
trast, the criteria for category assignment employed by a system of catego-
rization are potentially variable, allowing the membership of a category to
respond to the demands of the context in which it is used. In this way, the
membership of a category may vary across time based on the combination
of context-dependent and context-independent information that is used
to define category membership.
Differences in the criteria for assignment emphasize an important dis-
tinction between classification and categorization. In systems of classifica-
tion, class assignment relies on definitions that are “idealizations” or “the-
oretical abstractions” (Barsalou, 1987) to determine class membership. In
systems of categorization, however, category assignment is flexible and dy-
namic, reflecting the ability of the individual to modify category definitions
in response to variations in the immediate environment. Thus Barsalou
argues that
. . . the concepts that theorists “discover” for categories may never be
identical to an actual concept that someone uses. Instead, they may be
analytic fictions that are central tendencies or idealizations of actual
concepts. Although such theoretical abstractions may be useful or
sufficient for certain scientific purposes, it may be more fruitful and
accurate to describe the variety of concepts that can be constructed for
a category and to understand the process that generates them.
(Barsalou, 1987, p. 120)
(v) Typicality is closely related to the characteristics of membership and
criteria for assignment. However, typicality is potentially ambiguous: on the
530 library trends/winter 2004
one hand, typicality is used as an indication of the individual’s assessment
as to how representative a member is of its particular class or category; and,
on the other hand, it is used as a reflection of the assumptions regarding
membership and membership criteria that govern a system of classification
or categorization. Because empirical research indicates that subjects are
capable of ranking members according to typicality even when working with
well-defined, either/or classes such as odd number or even number (Armstrong,
Gleitman, & Gleitman, 1983), attempting to distinguish between classifica-
tion and categorization on the basis of an individual’s typicality judgments
would be an exercise in futility. In contrast, systemic assumptions govern-
ing membership do provide an important point of distinction between
classification and categorization.
In a system of classification, all members of a class must display the full
set of essential features prescribed by the class definition (see Proposition
I of the classical theory). It follows, then, that all members are assumed to
be equal and therefore equally representative of the class. For this reason,
the internal structure of a class is said to be ungraded because no entity can
be a “better” member of the class than any other member. However, in a
system of categorization, there is no assumption of equality of membership.
The fact that individuals can identify particular members as more typical
of a category reflects the dynamic nature of category definitions and the
corresponding variability of category membership as a reflection of imme-
diate context. The internal structure of a category is said to be ungraded
because it is possible to rank category members as to how typical or repre-
sentative they are of the category as a whole.
(vi) Structure is perhaps the single most important characteristic that
can be used to discriminate between systems of classification and categori-
zation because it is influenced by distinctions based on process, boundaries,
membership, and criteria for assignment. A classification system is gener-
ally a hierarchical structure of well-defined, mutually exclusive, and non-
overlapping classes nested in a series of superordinate-subordinate or ge-
nus-species relationships. The structure of a classification system provides
a powerful cognitive tool—an external scaffolding (Clark, 1997; Jacob 2001,
2002)—that minimizes the cognitive load on the individual by embedding
information about reality through the organization of classes within the
system. For example, because an entity either is or is not a member of a
particular class in a system of classification, it provides for determination
of class membership as a relatively simple pattern-matching or pattern-com-
pleting activity. At a more complex level, the structure of the classification
system establishes information-bearing relationships between classes: ver-
tical relationships between superordinate and subordinate classes that are
subject to the mechanism of inheritance illustrated above in the example
of the poodle Bleu; and lateral relationships between coordinate classes that
occur at the same level in the hierarchy and, when taken together, consti-
531jacob/classification and categorization
tute the immediately superordinate class within which they are nested. In
this fashion, the structure of a classification system serves as a medium for
the accumulation, storage, and communication of information associated
with each class in the structure; and, by capitalizing on the hierarchical and
lateral relationships between classes, it minimizes the information that must
be stored with each class and reduces the load on memory.
In contrast, the structure of a categorization system consists of variable
clusters of entities that may or may not be organized in a hierarchical struc-
ture. Because categories are not constrained by a requirement for mutual-
exclusivity, membership in one category does not prohibit membership in
any other category. More importantly, however, the very plasticity that is the
creative power of categories may actually prohibit the use of categorization
as a persistent information structure. The potentially transitory and over-
lapping nature of categories provides that any relationships established
between categories are themselves mutable. Thus a system of categorization
creates a conceptual framework whose meaning may be short-lived and
ephemeral—a conceptual framework that cannot function as cognitive
scaffolding and whose ability to serve as a medium for the accumulation,
storage, and communication of information is limited.
Ordering, Grouping, and Organization
A system for ordering (Jacob & Loehrlein, 2003) provides access to
resources by arranging them in some recognizable order. Typically, these
systems will employ alphanumeric or chronological sequences because
these arrangements generate syntactic patterns that are familiar to a ma-
jority of individuals. Although such a system is intended to support access
to known items, it may appear to create groupings of similar resources (e.g.,
all individuals with the last name Smith or alumni who graduated in the year
2000), but the imposition of sequential order is nonetheless a purely syn-
tactic device that cannot create meaningful relationships either between
individual entities or between groups of entities.
In contrast, a system of organization ( Jacob & Loehrlein, 2003) is a
unified structure that establishes a network of relationships among the class-
es or categories that comprise the system. These relationships are mean-
ingful and information-bearing because they specify principled connections
between two or more groups within the same system. Thus, with a single
possible exception, classification systems are systems of organization be-
cause they provide for the conceptual arrangement of a set of mutually
exclusive and nonoverlapping classes within a systematic structure of hier-
archical, genus-species relationships.
The exception is a constitutive classification (Jacob, Mostafa, & Quiro-
ga, 1997) consisting of a set of mutually exclusive classes that comprise the
totality of a given universe but lack nested, superordinate-subordinate re-
lationships. For example, the classes freshman, sophomore, junior, and
532 library trends/winter 2004
senior comprise the universe of college undergraduates. These classes ap-
pear to evince a hierarchical ordering (e.g., from freshman to senior), but
they fail to demonstrate meaningful, information-bearing relationships:
although a senior may be assumed to have been a junior at some point in
time, the class junior is not a true species of its purported superordinate
senior. Thus a constitutive classification does not qualify as a system of or-
ganization because, even though it is comprised of a set of mutually exclu-
sive and nonoverlapping classes that constitute the totality of a particular
universe, it fails to establish meaningful relationships between its constitu-
ent classes. It is interesting, too, that neither a hierarchical nor a constitu-
tive classification can serve as a system for ordering: because the distinctions
between classes are conceptual, the classes cannot conform to a recogniz-
able, syntactic pattern of arrangement. Furthermore, both hierarchical and
constitutive systems of classification require an index or other auxiliary
mechanism to support access, whether to unique resources or to individu-
al classes in the structure.
A system of categorization may or may not be a system of organization.
Although a categorization system groups entities on the basis of similarity,
the example of a constitutive classification demonstrates that the simple
identification of a set of categories without the establishment of meaning-
ful, information-bearing relationships does not constitute a system of or-
ganization. But, even though a categorization system does not indicate
meaningful relationships, it is not a system for ordering: the simple fact of
grouping entities into categories does not support access. Because catego-
rization reflects conceptual distinctions between groups of entities, it, too,
requires an auxiliary mechanism to provide access, whether to individual
categories or to unique category members.
If a system of categorization does not impose a systematic, syntactic
order on its member categories and if it does not establish meaningful re-
lationships between categories, then it is simply a mechanism for grouping.
For example, dividing the items on a shopping list into categories defined
by place of purchase (e.g., grocery store, gas station, and five-and-dime
store) is a mechanism for grouping that simplifies the individual’s interac-
tion with her environment but neither creates meaningful relationships
between categories nor imposes any recognizable order on them. A con-
stitutive classification is also an example of a simple mechanism for group-
ing: in this case, for dividing a universe of entities into a set of well-defined
and mutually exclusive groups without the identification of any meaning-
ful relationships among them.
Implications of Structure
The functional role of structure in the creation and enhancement of
information contexts can be addressed through analysis of four general
approaches to the organization and retrieval of resources: free-text search-
533jacob/classification and categorization
ing, postcoordinate indexing, precoordinate indexing, and classification
(see Figure 2). Although cognitive categorization serves as the baseline for
this analysis, it is removed from consideration as a system of organization,
not because it lacks semantic foundation or relational structure, but be-
cause, contrary to the arguments proffered by Shera (1956/1965), the or-
ganization imposed on cognitive categories is so dynamic and responsive
to changes in context that it cannot establish persistent, knowledge-bear-
ing relationships between categories.
Of the four general approaches to organization, free-text searching is
the least constrained. Although it shares with systems of classification the
creation of mutually exclusive, nonoverlapping, and rigidly bounded classes
whose membership is constrained by an explicit criterion of assignment
(i.e., the alphanumeric search string used to query the system), free-text
searching lacks an established set of principles that governs the structure
of classes and class relationships. It can be described as a system of catego-
rization in the very broadest sense, but it is, at best, a very elementary mech-
anism for grouping. Even as a grouping mechanism, however, it has two
significant flaws. In the first place, the basis for grouping is purely syntac-
tic: because the criterion for group assignment involves the simple match-
[Free-Text Searching]
Cognitive Categorization
Postcoordinate Systems
Precoordinate Systems
(subject headings)
Figure 2. Systems of Organization.
534 library trends/winter 2004
ing of alphanumeric strings, groups produced by this process share a su-
perficial similarity without deeper semantic implications. In the second
place, the process of free-text grouping is binary in that it generates only
two groups of entities—those that match the query string and those that
do not. However, because free-text searching lacks a semantic base, it can-
not support meaningful distinctions between these two classes, and, because
it exemplifies the very simplest of structures (i.e., two antonymous classes),
a free-text retrieval system cannot contribute to an information environ-
ment that will support or enhance the value of system output through the
establishment of meaningful context.
Unlike free-text searching, postcoordinate systems, precoordinate sys-
tems, and classification systems are all indexing systems in that each involves
the assignment to a resource of one or more descriptors intended to rep-
resent the intellectual content of that resource. These descriptors are usu-
ally drawn from a controlled vocabulary or indexing language that normal-
izes the vocabulary used in representation and retrieval by creating an
indexical, one-for-one correspondence between a descriptor and the con-
cept to which it points. The indexing language also provides for commu-
nication between the system and the individual by specifying the set of
authorized terms or subject strings that can be used to pose search queries
to the system. Although a descriptor may be a class label, a subject heading
or a single term or phrase, depending on the nature of the system, each
descriptor serves to identify or describe the intellectual content of a group
of resources. Unlike an access point in a system for ordering that supports
the retrieval of a unique entity, a descriptor is a surrogate for (or a pointer
to) the intellectual content shared by a group of resources. Indeed, index-
ing, like categorization, would be impossible if every resource were to be
treated as a unique entity.
In the progression from postcoordinate indexing systems through pre-
coordinate indexing systems to systems of classification, organizational struc-
ture becomes increasingly more constrained (see Figure 2). It is appropri-
ate, then, to begin this analysis with classification, the most highly
constrained of these three systems, and to work back through the less con-
strained systems toward the baseline of cognitive categorization.
Theoretically, a classificatory structure epitomizes a system of organi-
zation because it creates a principled structure of well-defined classes that
are linked by a system of hierarchical, genus-species relationships. Although
practice does not always adhere to theory in the development of classifica-
tion schemes, classification is nonetheless the most rigid of organizational
systems because its structure of mutually exclusive and nonoverlapping
classes mandates an absolute relationship between a resource and its class:
each resource may be assigned to one and only one class in the structure.
Thus the process of classification is inherently systematic because it is gov-
535jacob/classification and categorization
erned by a set of principles that serves as a persistent conceptual framework
for the creation of meaningful, structural relationships between classes.
Although the well-defined structure of a classification system provides
for the creation of meaningful, information-bearing relationships between
classes—relationships that facilitate the use of classification as an external
cognitive scaffolding—it places powerful limitations on communication
between the individual and the information system. In an information sys-
tem whose class structure is predetermined, the retrieval set returned for
any query posed to the system is necessarily limited to the membership of
a single class. Thus the structure of the classification system constrains the
questions that can be presented to the system by prescribing the set of
possible answers before a query has actually been posed. Within a classifi-
catory structure, then, communication is one-way—from the system to the
individual—and the individual must rely on her understanding of or intu-
itions about the structural relationships between classes in order to inter-
act with the system in an effective and meaningful way.
Information systems are identified as precoordinate when the catego-
ries or classes that comprise the system are either assigned or built by the
indexer at the time of indexing. A classification system is obviously a pre-
coordinate system because its classes are either established by the classifi-
cationist during scheme generation or built by the classifier at the time of
class assignment using a faceted vocabulary and a fixed citation order. A
subject heading system is also a precoordinate system but it is generally less
constrained—and less constraining—than a classification system. Where-
as classification mandates assignment of a resource to one and only one
class, a precoordinate system of subject headings does not require individ-
ual groups to be mutually exclusive. Rather, subject heading systems allow
for the assignment of multiple descriptors to a single resource, thereby
providing multiple access points for each entity rather than the single ac-
cess point (the unique class label) prescribed by a classification system.
Because it does not demand a well-defined and absolute relationship
between a resource and a subject heading—because it does not require that
the groups of entities associated with individual subject headings will nec-
essarily be mutually exclusive—a precoordinate subject heading system is,
in fact, a system of categorization. Categories formed by the subject head-
ing system are not rigidly bounded but frequently overlap, with individual
members spilling over into penumbral and even alien categories. Although
allowing multiple descriptors for a single resource provides for greater vari-
ability in the range of resources that can be retrieved with a single query,
the questions that can be posed to the information system are nonetheless
limited, as they are in a system of classification, by the authorized set of
subject heading strings that comprise the system. And, as with a classifica-
tion system, the retrieval set generated in response to a query is determined
536 library trends/winter 2004
by the indexer: the assignment of subject headings as descriptors not only
constrains the questions that can be posed to the system but serves to es-
tablish the specific set of resources that can be retrieved in response to each
query posed to the system.
Unlike the systematic and principled structure of a classification system,
the structure of a subject heading system is frequently unprincipled, unsys-
tematic and polyhierarchical. And, unlike the relationships established
between well-defined and mutually exclusive classes in a classification, any
relationships created between the categories of a subject heading system
cannot be assumed to be either meaningful or information-bearing. An
example from Subject Headings for Schools and Public Libraries (Fountain, 2001)
illustrates the lack of knowledge-bearing relationships that characterizes
many subject heading systems. The heading “Rats as carriers of disease”
combines two broader concepts: “rats” and “disease.” Although it is obvi-
ous that “Rats as carriers of disease” is somehow related to both rats and
disease, this heading is neither a kind of “Rat” nor a kind of “Disease.”
Because the specific value of any relationship that might link this heading
to its broader concepts is unidentified, the relationship must be supplied
by the individual if the heading is to be linked in a meaningful way to oth-
er concepts in the subject heading system.
Although subject heading systems appear to create relationships be-
tween headings, these relationships are often descriptive, idiosyncratic, and,
sometimes, potentially meaningless. For example, the Library of Congress
Subject Headings (Library of Congress. Cataloging Policy and Support Office,
Library Services, 2002) identifies the subject heading “Humanities” as the
broader term for the heading “Philosophy.” It then proceeds to list “Hu-
manism” as the broader term for “Humanities” and “Philosophy” as the
broader term for “Humanism.” Thus the supposed nesting structure is cir-
cular: “Philosophy” > “Humanities” > “Humanism” > “Philosophy.” Obvious-
ly, the absence of either a well-defined indexing language or principled and
meaningful relationships between subject headings undermines the abili-
ty of the system to establish a context that can contribute to the apprehen-
sion of information.
As with classification, communication between the individual and a
subject heading system tends to be one-way—from the system to the indi-
vidual—but the unprincipled structure of many subject heading systems and
the general lack of a prescriptive conceptual framework that can support
information-bearing relations undermines the potential for meaningful
communication between the user and the system. This is an important dis-
tinction between subject heading systems and the more structured classifi-
cation system that can be explained, in part, as a difference between the
processes of identification and predication. Classification involves a process
of identification (or definition) in that it asserts a meaningful, one-for-one
relationship between an entity and its class, but a precoordinate system of
537jacob/classification and categorization
subject headings involves a process of predication (or description) that
allows for multiple assertions to be ascribed to a single resource. While a
system based on predication demonstrates greater creativity, flexibility, and
hospitality than the well-defined structure of a system based on identifica-
tion, the very rigidity of the latter actually supports the creation and per-
sistence of information-bearing relationships that are simply not possible
in the looser structure of the former.
Precoordinate systems constrain communication between the individ-
ual and the system through the establishment of a finite collection of class
labels or subject headings that serve as the complete set of possible search
queries and predetermine the composition of retrieval sets. In contrast,
postcoordinate systems predetermine neither the queries nor the retrieval
sets but allow the individual to build her own category definitions that can
be presented to the system as search queries at the time of retrieval. Descrip-
tors representing the intellectual content of a resource are assigned by the
indexer at the time of indexing. During retrieval, the individual builds her
own search categories by combining descriptors with Boolean logic.
By allowing the individual to generate her own queries, the postcoor-
dinate system supports a more interactive form of communication between
searcher and system. In most postcoordinate systems, descriptors are as-
signed from a controlled vocabulary. In others, however, communication
between the individual and the information system is complicated by the
fact that the indexing language does not exist as a controlled vocabulary
but is extracted by the indexer from terms occurring in the resource be-
ing indexed. Generally, however, the generation of category definitions as
postcoordinate search queries is limited only by the set of individual terms
that comprise the indexing language. Although the resources that partici-
pate in a retrieval set are determined by the indexer’s assignment of descrip-
tors, communication between the system and the individual is greatly en-
hanced by her ability to create her own queries that will capture her
immediate information need.
Unfortunately, however, the flexibility of category generation, like the
process of cognitive categorization, goes hand-in-hand with the absence of
meaningful relationships. As with any free-text information system, posing
a query to a postcoordinate system simply divides the collection into two
groups: the set of resources whose assigned descriptors match the search
query and the remaining resources whose descriptors do not match the
query. Obviously, postcoordinate systems, like free-text systems, are simply
mechanisms for grouping, not systems of organization. Unlike free-text
systems, however, the basis for grouping in a postcoordinate system is se-
mantic, not syntactic. Although the postcoordinate system is simply match-
ing strings, the indexer imposes a certain level of conceptual control by
assigning simple descriptors from an indexing language that establishes an
indexical, one-for-one relationship between a descriptor and its referent.
538 library trends/winter 2004
The individual is empowered to create unique and potentially idiosyncrat-
ic search categories precisely because the system itself does not establish any
but the simplest categories—those defined by the individual descriptors
assigned by an indexer. Because the system fails to establish a principled
framework that provides for the establishment of information-bearing re-
lationships between categories, the postcoordinate system can neither cre-
ate nor contribute to an information context precisely because there is no
persistent structure that could support meaningful relationships between
This very preliminary review of the properties and features of the dif-
ferent approaches to organizing, ordering, or simply grouping information
resources has barely scratched the surface in addressing structural distinc-
tions between systems of classification and systems of categorization and how
these distinctions affect interaction with the system as an information en-
For example, at a very superficial level, the strength of classification is
its ability to establish relationships between classes that are stable and mean-
ingful. But the rigidity of structure that supports these relationships has its
corresponding disadvantages. In particular, traditional classification systems
are context-independent: because the relationships established by classifi-
cation are invariant and persist across time and space, these systems are
resilient to the context of use and severely constrain the individual’s abili-
ty to communicate with the system in a meaningful and productive man-
ner. In contrast, systems of categorization, and especially postcoordinate
systems, are highly responsive to—even dependent on—the immediate
context. The utility of these systems as information environments depends
ultimately on provisions for effective communication with the individual.
But the responsiveness and flexibility of the postcoordinate system effec-
tively prohibit the establishment of meaningful relationships because cat-
egories are created by the individual, not the system, and are thus fleeting
and ephemeral.
It is important for philosophers, theoreticians, and developers to work
toward a more in-depth and comprehensive understanding of how the struc-
ture of an information system contributes to the establishment of seman-
tic context; how different forms of organization support communication
between the searcher and the system; and how concrete organizational
structures and specific types of relationships contribute to the production
of meaningful information environments. The search for adequate expla-
nations of these issues will ultimately contribute to a deeper understand-
ing of the “dynamics of information” (Floridi, 2002) and the implications
that the structure of information systems holds for the composition of and
interaction with information environments.
539jacob/classification and categorization
I would like to thank Aaron Loehrlein for his thoughtful reading of and
commentary on preliminary drafts of this paper and for the many conver-
sations that contributed so richly to its theoretical content. I would also like
to thank Ken Herold for his very careful and insightful reading of the final
draft. This exploration of the role of structure in the generation of a se-
mantically meaningful information environment is in its nascent stages, and
I would like to thank Ken for the opportunity to develop these ideas for
presentation in this venue.
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... É nesta segunda fase classificatória, processada intelectualmente de forma lógica, aquela a que Gnoli (2016, p. 406) inclui na dimensão ontológica de um SOC. Estas duas fases assemelham-se à distinção efetuada por Jacob (1991Jacob ( , 2004 Phenomena (β) have been introduced as one among the dimensions of knowledge organization, also including reality in itself (α), perspectives under which phenomena can be considered (γ), their expression in documents (δ), their collections held in archives, libraries, and museums (ε), the information needs that motivate use of such collections (ζ), and people that experience one or another information need (η). … While all these dimensions except for α can be expressed in a classification, phenomena can be given priority, and the other dimensions can be connected to them by an analytico-synthetic notation. ...
... To be accurate, one cannot say that "class" is a synonym for "category", even though the terms are sometimes used in an interchangeable way (Jacob, 2004). The issue here is viewing categories either as natural or as constructed by humans. ...
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An organization of knowledge compartmented into disciplines does not prove adequate for a scientific praxis that lacks interdisciplinary openness. A potential solution involves a shift from an epistemological to an ontological focus on modulating new Knowledge Organization Systems (KOS). An ontological classification, of beings rather than knowledge, will focus on what, from the outset, is common to the various domains – the reality. At this juncture it is necessary to distinguish how knowledge is acquired and grounded from how reality is constituted and structured. This starting point involves an ancient controversy referred to as the question of universal cognition. A sustained position on this question is necessary for the consistent development of ontologically based KOS with the potential to better serve interdisciplinary practice. The aim is to contribute to clarify the ontological approach by contextualizing it in relation to universal cognition and concepts as units of knowledge of KOS, empirically complementing the study with a comparison between the ontological approaches of two KOS: Integrative Levels Classification (ILC) and Basic Formal Ontology (BFO). We aim to: i. schematizes the requirements of an ontological system; ii. present an overview of the universal cognition issue; iii. identify the main modes of existence attributed to concepts and their suitability to SOC units; iv. characterize ILC and BFO ontological approaches; v. systematizes recommendations to help modeling ontological KOS. To fulfill these objectives the analytical hermeneutic-dialectical and comparative methods were used. We concluded that an ontological KOS starts from an ontological analysis, i.e., a categorization of existing entity types that can be objectively subsumed under distinguishable categories. The resulting system may not rigorously define the entities it incorporates and the relationships between them, as happens in ILC. In ILC the integration of the epistemological dimension is explicitly sought, and the naturalness of its classes is expressed only implicitly. The concepts continue to be understood as elementary pieces of KOS, with a formulation very similar to that of Dahlberg. In BFO, not only is it explicit its concern to contain only natural classes, but concepts are only understood as cognitive tools for accessing reality. The system, in addition to rigorous definitions, results from rigorous ontological and an adequacy to reality outside itself. These are the characteristics of an ontological model that distinguishes itself from systems with more permissive approaches, derived from the non-rigorous definition of its constituents or from the non-application of the aforementioned rigorous philosophical analysis. Within the scope of KOS, the inadequacy of the psychological interpretation of concepts became evident, given their individual nature as mental entities. From the linguistic perspective, concepts are commonly interpreted as labels for their meanings, which are associated with the epistemological reading. In the latter, if its scope does not promote the separation between uniquely intentional objects and others of a different nature, its application to the development of ontological KOS will be problematic. Different specifications concerning the nature of reality are imposed by different epistemic positions. It was possible to verify a lowest common denominator for this reality. Whether the positions are considered realist, nominalist or conceptualist, directly or indirectly, the support of human perceptions is placed on something independent of them. Despite the potential imperfections of human perceptions, they will not be simply, or solely, about themselves. In this context, five recommendations are proposed to help modulate ontological SOC: i. provide precise and ontologically consistent definitions of the classes to be included; ii. clearly differentiate classes from their particular instances; iii. classify based on intrinsic traits belonging to the respective entities; iv. not represent the data of a particular database, but the types of entities existing in the domain to which the data report; v. use cognitive representations as a means to represent existing entities in the respective domain and not as an element to be represented. These recommendations are intended as a starting point for future development and not as a panacea for the issues involved. The present thesis does not intend to be a complete or definitive answer to the addressed question, but it is expected to have enough detail, so that, in the context of Information Science, the ontological approach is better understood and seen as a viable alternative to the epistemological one.
... There are many other definitions of information (Jacob 2004), of which Bateson's (1973) "difference that makes a difference" is probably the most useful from a biological or cybernetic point of view. ...
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An extract from my unfinished book, Application Holy Wars or a New Reformation - A Fugue on the Theory of Knowledge (Rev. 26/4/2014) William P Hall (Kororoit Institute)
... À l'inverse, les folksonomies, vocabulaires non structurés par essence, ne dépendent pas d'une création en amont par des professionnels et vivent au rythme de l'évolution du langage des utilisateurs. Elles ne sont pas des classifications à proprement parlé, mais plutôt des « catégorisations sociales horizontales » (Jacob, 2004); Munk & Mørk, 2007). Selon (Ihadjadene et Favier, 2008), ces modes collaboratifs d'accès à l'information conduisent certains à considérer que « la popularité se substitue à l'autorité tandis que l'influence remplace la pertinence (Olivier Le Deuff 2006 116 ; (Millen & Feinberg, 2006) »En contrepartie, les folksonomies ont des limites inhérentes à leurs natures chaotiques, telles que la multiplication des synonymes, fautes d'orthographes, etc. Par exemple, sur Flickr, une photographie peut être tagguée : fleur, fleurs, flower etc. Il s'agit strictement des mêmes termes, mais ceux-ci ne sont pas fusionnés au détriment de la recherche d'information. ...
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Our thesis takes place in a global video game (VG) company. In this world where there are many restrictions on information accessibility, where projects usually managed locally are now developed interstudio, its actors are faced with multiple knowledge silos and KM becomes a challenge even more strategic. What are the sources used by VG employees, the criteria applied and the barriers they encounter? How are web 2.0 tools positioned within this digital workplace? What should be the mandatory pillars to deploy a corporate folksonomy? Using Savolainen’s information horizon methodology, we conducted an exploratory study based on interviews organized at the Ubisoft Montreal studio. Our 29 participants had to place their sources of information on mind maps. Theses maps and interviews transcripts are supplemented by some data related to the deployment of the company's tags. We propose a new categorization of sources and confirm the typology of Savolainen criteria. We shed light on the impact of a variable temporality between production and support teams on their information practices. We attest that the conditions of the folksonomy deployment did not allow the initial associated vision to be applied. The results of our survey on the informational practices of video game employees could find application in strategic knowledge management. We affirm that folksonomies can still play a major role if they fully benefit from the technological support necessary for their deployment. They could thus help to facilitate the information paths of the employee for whom the primary sources of information remain the other employees and tools which allow them to communicate together. Notre thèse se déroule dans une entreprise mondiale vidéo ludique. Dans cet univers où les restrictions d’accès à l’information sont nombreuses, où les projets habituellement gérés par lieux sont désormais développés inter studios, les acteurs y sont confrontés à de nombreux silos et le KM devient un enjeu d’autant plus stratégique. Quelles sont les sources d’information que les acteurs du jeu vidéo utilisent, les critères qu’ils appliquent et les barrières qu’ils rencontrent ? Comment sont positionnés les outils web 2.0 dans ce paysage numérique ? Quels axes de déploiement pour une folksonomie d’entreprise ? En suivant la méthodologie horizon informationnel de Savolainen, notre étude exploratoire repose sur des entretiens menés au studio Ubisoft de Montréal où nos 29 participants plaçaient leurs sources d’information sur des cartes mentales. Ces données sont complétées par celles relatives au déploiement des tags dans l’organisation. Nous proposons une nouvelle catégorisation de sources et confirmons la typologie de critères de Savolainen. Nous éclairons l’impact d’une temporalité variable entre les équipes de production et support sur leurs pratiques informationnelles. Nous constatons que le déploiement de la folksonomie n’a pas permis d’appliquer la vision initiale associée. Nous affirmons que les folksonomies peuvent encore jouer un rôle majeur dans ces applications si elles bénéficient du support technologique nécessaire à leur déploiement. Elles contribueraient ainsi à la facilitation du parcours informationnels des acteurs de l’organisation, pour qui les premières sources d’information restent les collaborateurs et les outils pour échanger ensemble.
... As discussed in detail in the previous section, categorisation encompasses the processes of comparing various objects' characteristics and arranging them according to their recognised featural, functional or semantic similarity. Classification, on the other hand, refers to three distinct but closely related concepts: (1) an organised system of classes (i.e., collection of informational resources or representations); (2) a group or class within that system; or (3) the process of assigning entities to classes in the classification system (more detailed discussion about the differences between categorisation and classification see : Jacob, 2004). Classification is best exemplified by the existence of various taxonomies. ...
Auditory categorisation is a function of sensory perception which allows humans to generalise across many different sounds present in the environment and classify them into behaviourally relevant categories. These categories cover not only the variance of acoustic properties of the signal but also a wide variety of sound sources. However, it is unclear to what extent the acoustic structure of sound is associated with, and conveys, different facets of semantic category information. Whether people use such data and what drives their decisions when both acoustic and semantic information about the sound is available, also remains unknown. To answer these questions, we used the existing methods broadly practised in linguistics, acoustics and cognitive science, and bridged these domains by delineating their shared space. Firstly, we took a model-free exploratory approach to examine the underlying structure and inherent patterns in our dataset. To this end, we ran principal components, clustering and multidimensional scaling analyses. At the same time, we drew sound labels’ semantic space topography based on corpus-based word embeddings vectors. We then built an LDA model predicting class membership and compared the model-free approach and model predictions with the actual taxonomy. Finally, by conducting a series of web-based behavioural experiments, we investigated whether acoustic and semantic topographies relate to perceptual judgements. This analysis pipeline showed that natural sound categories could be successfully predicted based on the acoustic information alone and that perception of natural sound categories has some acoustic grounding. Results from our studies help to recognise the role of physical sound characteristics and their meaning in the process of sound perception and give an invaluable insight into the mechanisms governing the machine-based and human classifications.
... In particular, the generic relations of hierarchically nested monothetic classes due to their transitive and asymmetric character enable deductive reasoning that exploits the inheritance of properties from a superordinate class to its subordinate classes (Kwasnik 1999). Examples of polythetic classifications, according to Elin K. Jacob (2004), can be found in subject headings that may or may not form hierarchical structures but are frequently unprincipled and unsystematic. She argues that systems based on polythetic classes are more flexible, creative, and responsive to context but less suitable to function as persistent information structures due to their mutable and ephemeral character. ...
Conference Paper
Across disciplines concerned with human categorization like psychology, anthropology, linguistics, and philosophy, there is a well-established distinction between monothetic and polythetic approaches to the formation and use of categories, concepts, and classes. This is often contrasted as the classical view versus the prototype theory. While monothetic classification is based on classes that are defined by a set of necessary and sufficient properties shared by all of its members, polythetic classification is based on classes in which members share a significant number of properties but none of these has to be found in all members. In the field of knowledge organization, the monothetic-polythetic distinction presents “a difference that makes a difference” (Jacob 2004, 515) and it has been emphasized that since human cognition can shift seamlessly between both forms of representation, there is a need for “multilevel approaches” (Priss 2001, 60). This paper takes a cognitive-developmental perspective and argues that polythetic classification precedes monothetic classification in both individual and collective development. It is suggested that the classical view and the prototype theory are simply concerned with different developmental stages of classificatory cognition that coexist in the human mind as Integrative Levels of Knowing. Thus, a more comprehensive framework that includes both of them offers comparative tools for cross-cultural and historical analyses of knowledge organization systems like library classifications, and of collective representations like symbolic classifications and folk taxonomies.
A published review of Eric Scerri's The Periodic Table, by information and library science professor Birger Hjorland which led to a 3 person debate on the nature of classification in general and in chemistry in particular.
Construction is an essential contributor for both developed and developing economies. Corruption, schedule delays, cost overruns, and erratic project performance are common few problems that face the conventional procurement process of any organization. This research focused on the weakness of current procurement practices in public construction projects in Iraq, as stated by the World Bank and Organization for Economic Cooperation and Development (OECD) reports. The methodology of this study was to collect data by conducting a thorough systematic search of existing literature. The authors used QDA Miner 4 software for coding and thematic categorization. The study found 42 variables from previous studies, and the authors distributed these variables into 12 thematic divisions representing the organization's key performance indicators (KPIs). The authors conclude that these indicators are important to introduce many frameworks for the integration of procurement process in developing countries. For future studies, there is a possibility to introduce an integrated construction and design framework to enhance organizational performance and the procurement process.
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What is the relationship between language and animal communication? This has largely been discussed within research on language evolution and disciplines beyond linguistics, but impacts upon the study of language generally. There are two extant views on the nature of this relationship: either there is a stark divide, with language considered as completely unique to humans, or there is a linear continuum from animal communication to language, aligning with gradualist evolutionary principles. Yet, each view involves considerable limitations. Moreover, there is no agreed-upon definition of language, which further complicates the determination of its relationship with animal communication. Withdrawing from attempts to define language with traditional fixed criteria (as characteristic of classical categorisation), this article suggests a different approach to conceptualising language and assessing the concept’s applicability to other species. Categorising phenomena through family resemblances and graded typicality of features (as in prototype-based categorisation) enables a new approach to conceptualising language, its typological diversity amongst humans, and the systematic integration of animal communication. Ultimately, with an illustrative model, this article proposes a strong overlap of animal communication with language. This approach illuminates more of the nature of language, facilitates more cohesive interdisciplinary research, and introduces potentially positive ethical implications for non-humans.
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This study is part of a wider research pursued over the years and still in progress, whose aim is to highlight patterns of cross-linguistic encoding through the interpretation of divergences in cross-linguistic categorization. The interaction among "language", "category" and "classification" is investigated along with the role of "fuzziness" (or rather "vagueness"). The extent of "context" in disambiguation and translatability is taken into consideration as is the role of "scripts and frames". A further examination of the "deictic pivot" (partly introduced in Nannini 2018) as one of the features outlining "spaces of codified knowledge" is also investigated.
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Cyber-physical systems (CPS) offer great potential for the digital transformation of industrial value creation in the context of Industry 4.0. They unify and integrate several technological approaches, including big data analysis and artificial intelligence, enhancing real-time monitoring and control of manufacturing processes. An extensive knowledge base formed by various disciplines, including information systems, engineering, and computer science, already exists for CPS. However, this knowledge has not been holistically captured and structured to date. To address this research gap, this study conducts a large-scale literature review of 2365 papers representing the current state of the research and then develops a novel categorization on industrial CPS with 10 sections, 32 areas, and 246 fields. The categorization is presented in hierarchical graphical form and can also be utilized as a web tool. To conclude, a perspective on future research needs and potentials to enhance Industry 4.0 in both research and practice are offered.
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It is the intent of this paper to demonstrate that the processes of classification and categorization are actually two separate and distinct processes. The classical theory of categories is described, the major arguments against it are reviewed, and alternative approaches to the structure of categories are discussed. The apparent failure of the classical theory to account for the instability observed in category membership is attributed to the underlying assumption that the terms "classification" and "categorization" refer to the same process. The possibility that an interactive functional relationship exists between classification and categorization is advanced on the basis of the individual's need to communicate.
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Categorizations which humans make of the concrete world are not arbitrary but highly determined. In taxonomies of concrete objects, there is one level of abstraction at which the most basic category cuts are made. Basic categories are those which carry the most information, possess the highest category cue validity, and are, thus, the most differentiated from one another. The four experiments of Part I define basic objects by demonstrating that in taxonomies of common concrete nouns in English based on class inclusion, basic objects are the most inclusive categories whose members: (a) possess significant numbers of attributes in common, (b) have motor programs which are similar to one another, (c) have similar shapes, and (d) can be identified from averaged shapes of members of the class. The eight experiments of Part II explore implications of the structure of categories. Basic objects are shown to be the most inclusive categories for which a concrete image of the category as a whole can be formed, to be the first categorizations made during perception of the environment, to be the earliest categories sorted and earliest named by children, and to be the categories most codable, most coded, and most necessary in language.