1. Module 9a: Classification Schemes
IMT530: Organization of Information Resources
Winter, 2007
Michael Crandall

2. 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
IMT530- Organization of Information Resources

3. Module 9a Outline What is a classification system?
Types of classifications
Characteristics of classifications
Taxonomies
Classification vs. categorization
Purposes of classification
IMT530- Organization of Information Resources

4. 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
Schedules (hierarchies):
Are the sum of the hierarchies devoted to a particular discipline; may be that a discipline consists of more than one hierarchy.
Schedules represent a set of hierarchical relationships
Notation is given to indicate the meaning of a particular class (e.g., 677 means “Textiles” in DDC; also included in the meaning is its context, which is Technology / Manufacturing).
Notation is frequently numbers, or it may be a combination of numbers, letters, and punctuation.
The third part of a traditional classification scheme is the alphabetical index to the schedules.
An index that indexes an entire classification scheme is called a “relative index.”
DDC and UDC have relative indexes; the LCC does not, but has separate indexes for each schedule.
IMT530- Organization of Information Resources

5. Two Types of Classification Systems
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:
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)
IMT530- Organization of Information Resources

6. IMT530- Organization of Information Resources

7. IMT530- Organization of Information Resources

8. 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
Expressiveness refers to how much you can tell by looking at the notation about the placement and relationships of a class-- as in Dewey, which uses decimals to show depth in the classification structure. LCC’s notation is very unexpressive- you can’t tell much about the class by the letters and numbers used to identify it.
Hospitality refers to the ability to expand the notation– either in chains or in arrays (DDC: very hospitable in chain (because it is decimal based), not so in array (you can only ever have 10 sisters in an array))
IMT530- Organization of Information Resources

9. Classification Example: DDC
Meaning of number is created by the context of the hierarchy. For example “inherent features” means “inherent features of photographs” – this is implied in the hierarchical structure.
IMT530- Organization of Information Resources

10. 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
IMT530- Organization of Information Resources

11. 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
IMT530- Organization of Information Resources

12. 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:
(its meaning, or hierarchy, in Dewey, is: Arts > Drawing and Decorative Arts > Decorative Arts > Handicrafts > In papers > Papier-mâché)
IMT530- Organization of Information Resources

13. 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 pre-coordinated – almost all terms contain multiple concepts in that they carry with them the concepts inherent in an entire subject hierarchy
IMT530- Organization of Information Resources

14. 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
IMT530- Organization of Information Resources

15. 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
IMT530- Organization of Information Resources

16. Yahoo Taxonomy
Yahoo Directory is a large taxonomy-
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 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
Try these explorations on your own to see how a large taxonomy works
Go to Yahoo Directory (
Click on “Science”
Click on “biology”
Click on “zoology”
Click on “animals, insects, and pets”
What kind of category is “Complete list of animals by name”?
Under additional categories, click on “Pets”
Again, what kind of category is “by Animal”?
Click on “disabled pets” and notice the taxonomic string at the top beginning with “Directory>…”
Go back to the main directory page
Click on “Science” again
Click this time on “Animals, Insects, and (note
Look at the taxonomic string (term) at the top of your screen – it is: Science > Biology > Zoology > “Animals, Insects, and Pets” – so indicates a class out of it’s hierarchical position, used as a reference (check out Booksellers under Science – what is its hierarchical position?)
IMT530- Organization of Information Resources

17. 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
IMT530- Organization of Information Resources

18. Sample categorization – the “Idea Index”
IMT530- Organization of Information Resources

19. 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)
IMT530- Organization of Information Resources

20. Purposes of Classification Systems
To group topics or physical items on the same subject together (collocation) to promote browsing
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
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
IMT530- Organization of Information Resources

21. Purposes of Classification Systems
Placing of an item in a classification gives us rich information about that item and its context
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
IMT530- Organization of Information Resources

22. More Purposes of Classification
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
Note that these purposes are suspiciously familiar- they are essentially Cutter’s Objects of the Catalog
IMT530- Organization of Information Resources

23. Questions?
IMT530- Organization of Information Resources

24. 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!!!
IMT530- Organization of Information Resources