Taxonomies and Classification for Organizing Content Prentiss Riddle INF 385E 9/21/2006

What is a taxonomy? A hierarchical classification system in which categories are subdivided to create finer distinctions. animal –vertebrates mammals –cat –dog reptiles –invertebrates vegetable mineral

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

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 

Beyond taxonomies

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 –War - History - U.S –U.S. - History War Or in more familiar terms: –Wine - Red - California - Dry Under $25 –Wine - Under $25 - Red - Dry - California –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 – –del.icio.usdel.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