the Dewey Decimal System's categorization for religions of the world, which is the 200 category.
Dewey, 200: Religion
210 Natural theology
220 Bible
230 Christian theology
240 Christian moral & devotional theology
250 Christian orders & local church
260 Christian social theology
270 Christian church history
280 Christian sects & denominations
290 Other religions
link: http://www.shirky.com/writings/ontology_overrated.html