Facet analysis is the process of breaking down a subject into its component parts, choosing appropriate terminology to express those parts, and conveying those aspects by means of a notational device (Spiteri, 1998). This method was originally devised by S. R. Ranganathan (1962) when describing colon classification, a faceted classification scheme. Faceted search is made possible by facet analysis.
To hear some DAM professionals talk about it, faceted search is the best thing since buttered toast. With good reason too. In a faceted classification structure objects can ‘exist’ in several different locations versus being forced into a single node as in a hierarchical structure. Documents become easier to find in a faceted taxonomy because they are indexed exhaustively, allowing users to search results according to a range of qualities. In effect, faceted organizational structures flatten complex taxonomies allowing collections of digital assets to be browsed.
Examples of faceted classification:
Art and Architecture Thesaurus® Online
Library of Congress Classification System
Examples of faceted search:
Amazon Instant Video (UK)
National Film Board of Canada (films by subject)
In the field of information science, the output of facet analysis is usually a taxonomy that displays relationships between terms to be used in subject classification of digital assets (see Boxes and Arrows for an example). Single concepts must be identified and distinguished from one another. These concepts may be post-coordinated (synthesized) at the point of information retrieval.
Example of faceted terms:
Example of post-coordination:
Male – Russian
According to Ranganathan (1967), facets must be mutually exclusive, homogenous, reflect the purpose, subject and scope of the classification system, and be exhaustive. In other words facets should completely describe the subject using terms that are distinguishable from one another. The index terms should also reflect current usage in the subject field.
Generally speaking, there are five steps to facet analysis.
- collect a representative sample of the assets
- create a one sentence statement that represents what each item is about
- extract indexable concepts (entities) from these statements
- break apart any compound subjects
- organize into categories
Ranganathan (1967) came up with five fundamental categories (PMEST):
- Personality: something or someone in question (Who)
- Matter: aspects personality is made of (What)
- Energy: how personality changes, is processed, evolves (How)
- Space: place, location, environment personality exists (Where)
- Time: dates, periods, etc. action takes place (When)
If you’re left needing a broader set, Broughton (2001) came up with thirteen (more granular) categories.
Or make up your own!
There exists no categories that are fundamental to all subjects. Categories should be derived based on the subject being analyzed (Spitery, 1998).
The resulting structure will be the basis for a taxonomy. Next up: organize, test, deploy, rinse, and repeat.
How have you approached controlled vocabulary design for digital assets?
Denton, W. (2003, November). How to Make a Faceted Classification and Put It On the Web. Retrieved from http://www.miskatonic.org/library/facet-web-howto.html
Spiteri, L. (1998). A simplified model for facet analysis: Ranganathan 101. Canadian Journal of Information and Library Science, 23(1/2), 1–30. Retrieved from http://iainstitute.org/en/learn/research/a_simplified_model_for_facet_analysis.php
Here’s an example I use to describe facetted search to others – imagine looking for a nice bottle of wine on [insert any well known large online wine retailer]. As an example, here is the text off a local wine chain website:
Cabernet Sauvignon (174)
Pinot Noir (121)
Sauvignon Blanc (161)
Shiraz / Syrah (372)
View more varieties (1,192)
Fortified Wine (59)
Red Wine (1,160)
Rosé Wine (44)
Sparkling Wine & Champagne (215)
White Wine (752)
View more wine types (3)
De Bortoli (22)
Peter Lehmann (34)
View more brands (2,056)
New Zealand (195)
View more countries (53)
More facets etc
So you can look for the same bottle of wine in lots of different ways (or facets). It is not a hierarchical structure, so it exists in all facets simultaneously. Most people I have spoken to understand this intuitive example immediately. And who knows, you might even find you are talking with a fellow wine lover!
Thanks Philip, wonderful example! I have been struggling to understand facet analysis in my information science program and this has really helped.