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Taxonomies and Classification for Organizing Content. Prentiss Riddle INF 385E 9/21/2006. A hierarchical classification system in which categories are subdivided to create finer distinctions. animal vertebrates mammals cat dog reptiles invertebrates vegetable mineral.
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Taxonomies and Classification for Organizing Content Prentiss Riddle INF 385E 9/21/2006
A hierarchical classification system in which categories are subdivided to create finer distinctions. animal vertebrates mammals cat dog reptiles invertebrates vegetable mineral What is a taxonomy?
Not all classification systems are taxonomies Richard Saul Wurman’s LATCH • Location • Alphabet • Time • Category • Hierarchy Any of these can be expressed as a taxonomy or not. (Well, maybe not the alphabet...)
A quibble about definitions • We commonly use “taxonomy,” “hierarchy” and “classification system” interchangeably but in fact they’re distinct (if overlapping) terms • In particular, a hierarchy can be linear • the “H” in Richard Saul Wurman’s LATCH • elephant > horse > dog > mouse • Maslow’s hierarchy of needs • A “folksonomy” is not a taxonomy!
Why taxonomies? Taxonomies in our heads • Fundamental to cognition • Observed in children from an early age • Long before Linnaeus and Darwin: “folk taxonomies”
Why taxonomies? Taxonomies in the world • Genealogy, phylogeny • Command structures, org charts, territories • Filesystems, domain names, URLs /var/www/people/faculty.php www.ischool.utexas.edu http://www.ischool.utexas.edu/people/faculty.php
This suggests the use of taxonomies in IA • Taxonomies in support of browsing • Taxonomies in support of search But that’s problematic...
Problematic in the world • The world is complicated Who here has had cataloguing? LC Subject Headings, LC Classification, Dewey... • The world is even more complicated • Lattices and networks, not trees • Multiple kinds of relationships • Fuzzy boundaries
Problematic in our heads • The taxonomies in our heads don’t match the world • The available taxonomies may not be what’s important anyway • The user doesn’t care about the org chart! (The mantra of enterprise IA) • The user doesn’t care about the filesystem
Cautious use of taxonomies • Tempered by understanding and testing users • Enlist users in creating taxonomies • Techniques like card sorting • Functional or “folk” etymologies preferred over official ones • A gardening site might classify plants by temperature, sun and water needs, not by botanical classification • Make official taxonomies available behind the scenes for use by experts (departmental admins, biology wonks)
Taxonomies in support of browsing “Umbrella architecture” (Rosenfeld & Morville) E.g., familiar hierarchical menu structures
Taxonomies in support of browsing Not always ideal...
Taxonomies in support of browsing ...but better than chaos. • Supports breadcrumbs • If the users don’t know your taxonomy, gives them a fighting chance to learn it.
Browsing very large taxonomies Yahoo began as a taxonomy company ...although at some point it became a search (and content) company
Taxonomies in support of search Search results can include a link to a category
Taxonomies in support of search And searches can be limited to a category
Taxonomies on steroids Taxonomy + controlled vocabulary = thesaurus A thesaurus usually has a taxonomy embedded in it
Relationships in a thesaurus • Some of the links in a thesaurus express hierarchy and links across it • Broader term (BT) • Narrower term (NT) • Related term (RT) • Some express the controlled vocabulary • Preferred term (PT) • Variant term (VT) • Use (U) • Used for (UF)
Not just synonyms • A thesaurus is not just for synonym rings cat = feline = kitten= kittycat • It’s also for key relationships across the hierarchy “Nice pants! How about a shirt?” In a sense, Amazon’s many suggestion features and much of Google Adwords are a set of RT links in a thesaurus
Faceted classification A problem inherent in taxonomies is, what gets divided first? • History - U.S. - War - 1812 • War - History - U.S. - 1812 • U.S. - History - 1812 - War Or in more familiar terms: • Wine - Red - California - Dry - 1999- Under $25 • Wine - Under $25 - Red - Dry - California - 1999 • etc.
Facets are independent hierarchies • Facets work in parallel • In the subject classification example: facets for topic, time, place, etc. • In the wine example: facets for type, origin, price, manufacturer, etc. • A particular item will be at the intersection of several facets • Facets can simplify classification systems both for creators and users
Folksonomies • Fun, powerful, interesting but a misnomer: not taxonomies at all • Tagging systems in use in popular “web 2.0” sites • www.flickr.com • del.icio.us • Personal keyword metadata aggregated for searching and browsing • The result is not a hierarchy, not really a classification system, certainly not a taxonomy