Module 9a: Classification Schemes
IMT530: Organization of Information Resources
Winter, 2008
Michael Crandall
Recap
• Hierarchical and faceted approaches are not
mutually exclusive
– You can use hierarchies under facets to help with
entry vocabulary and cross references
• You may not always be able to apply mutual
exclusion and exhaustivity to facets, but you
should use these principles to help clarify
– Spiteri’s Idea Plane is where you do this work
– Try to apply terms from all facets to each object
(webpage) you’re tagging to see what happens
– If it doesn’t make sense, you probably need to
rethink your facets
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Module 9a Outline
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What is a classification system?
Types of classifications
Characteristics of classifications
Taxonomies
Classification vs. categorization
Purposes of classification
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What Makes a Classification?
• A verbal description of concepts represented
in the scheme
• An arrangement of these descriptions in a
classed or logical order for users (schedules)
• A notation that shows the logical order
• References to guide users to related aspects
in the scheme
• An alphabetical index that leads to the
notations
• Instructions for use
• A maintenance organization
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Two Types of Classification Systems
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Classed – e.g., classification schemes such
as Dewey Decimal Classification (DDC)
Alphabetico-classed – e.g., taxonomies such
as Yahoo’s categories
Both share common characteristics:
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Classes- the smallest component of a subject
hierarchy (each node is a class, composed of
subclasses)
Arrays- comprised of all “sister” classes that have
the same “mother”; e.g., “roller chairs” and
“straight back chairs” comprise one array, etc.
Chains- a string of classes that move up and
down a hierarchy (breadcrumb trail on the web)
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Classed Systems: Definition
• Classed systems use notation as terms
• Notation frequently includes combinations of
numbers, letters, and punctuation
• Notations always have a meaning, which is
frequently not understandable by just looking
at the notation itself (i.e., the DDC number
517 has a meaning)
• Notation may be expressive or hospitable
• The Library of Congress Classification (LCC)
is an example of a classed system
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Classification Example: DDC
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Alphabetico-Classed Systems: Definition
• Alphabetico-classed systems are
classifications that use words as terms
instead of notation
• Like classed systems, hierarchical structure
and meaning are inherent in each term
• Because words are used in terms, the terms
are usually understandable without
interpretation by an expert
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Alphabetico-classed Systems
• An example of current alphabetico-classed
systems are web-based taxonomies
• However, alphabetico-classed systems have
a long history of use in knowledge
organization in encyclopedias and library
catalogs
• They did not work well in most manual
environments because subjects often got
buried very quickly and were difficult to find if
you didn’t know the hierarchy in which they
were embedded
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Contrasting Alphabetico-classed
and Classed Terms
• Sample alphabetico-classed term for
papier mâché:
– Arts and Humanities > Visual Arts >
Sculpture > Papier Maché
• Sample DDC classification number
(term) for paper mache:
– 745.542 (its meaning, or hierarchy, in
Dewey, is: Arts > Drawing and Decorative
Arts > Decorative Arts > Handicrafts > In
papers > Papier-mâché)
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Classifications are Pre-Coordinated
• Notice that in both of the papier mache
examples, both of the terms carry the
meaning of an entire hierarchy
• Because of this, all classifications are precoordinated – almost all terms contain
multiple concepts in that they carry with them
the concepts inherent in an entire subject
hierarchy
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Classification in Libraries
• Driven by need to arrange materials and
provide systematic access
• Traugott Koch’s types of classification
schemes reflect this
– Universal schemes- DDC, UDC, LCC
– National schemes
– Subject specific schemes- NLM, EI
• Issues discussed in Taylor relate to this
function of classification
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Snoopy
• Bertolucci points out the need to move
beyond the general classification schemes
used in libraries for most local applications
– Points out different drivers and different user
populations
– Usually constrained by narrower needs
– Often are built for temporary use
• These smaller classification structures are
often lumped under the term “taxonomies”
• Most likely to be the model you will encounter
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Yahoo Taxonomy
• Yahoo Directory is a large taxonomyhttp://dir.yahoo.com
• Although each term in the taxonomy stands for a
particular subject or class (e.g., “Disabled pets”), the
term itself carries the meaning or context of the entire
domain in which it is situated (“Science > Biology >
Zoology > Animals, Insects, and Pets > Pets >
Disabled Pets”)
• Cross-references to related classes out of the current
sequence are indicated by the @ symbol (similar to a
“see also” reference in a CV)
• In web taxonomies, you can either browse to an term
embedded in a hierarchy (e.g., disabled pets), or
search on it to retrieve it immediately
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Classification vs. Categorization
• Classification is different from categorization
• Categorization is grouping based on common
characteristics (ordering and establishing
hierarchical relationships is not necessarily
involved)
• Categorization is used often in the information
professions – pamphlet files, vertical files, and
websites
• If there are very few files and all are visible,
there is usually not a particular need for
ordering or hierarchical structuring
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Sample categorization – the “Idea Index”
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Ways of Building Classifications
• Bottom-up
– Classes are developed empirically, through
observation of cases (sometimes called
taxonomy; in LIS, bottom-up systems are
often a result of literary warrant policies)
• Top-down
– Classes are developed conceptually;
observation of cases is not involved
(sometimes called typology)
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Purposes of Classification Systems
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To group topics or physical items on the
same subject together (collocation) to
promote browsing
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Classification by discipline or domain makes
possible browsing in the context of a discipline or
domain
Browsing helps us to become aware of items that
we did not previously know about
To fix a topic or item at a particular location
and context in the universe of knowledge
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All items are placed in context with all other items
– each item has a location which may be
contrasted or compared to the location of every
other item
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Purposes of Classification Systems
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Placing of an item in a classification gives us
rich information about that item and its
context
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James Welch, Fool’s Crow (assigned the LCC
class number PS 3573.E44)
PS3573.E44 = American Literature, 1960-, “W”
authors, James Welch
In a taxonomy, Welch’s novel might be placed in
this kind of context: American literature > 20th
century > Northwest fiction
In a physical arrangement, a person can learn
something about Fool’s Crow by what other items
it resides next to
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More Purposes of Classification
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To provide a location device based on
subject content for individual items that
will help user locate a particular item
– In libraries, classification numbers are
used for storing physical documents, and
for returning them to their place when
they’ve been removed
– In taxonomies, you can guide users to
similar content through breadcrumb trails
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Questions?
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Exercise 9a
• Spend the next 45 minutes exploring the
examples in Exercise 9a
• Ask questions and talk!!!
• Be sure to hand in completed work at
the end of class for credit!!!
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