Ontology: a term created by Christian Wolff, german philosopher in the 18th century. The intetion was to denote a sub-area of philosophy to study the theory of being. An ontology states a false or true statment about he world.
Taxonomy, the science of classification in a broad sense, is usually restricted to biological classification and specially to the classification of plants, ans animals. Is name come from Greek: taxis (arragement) and nomn (law) . The seven basic (obligatory) taxonomic categories to identify and classify organisms are:
Kingdon, Phylum, Class, Order, Family, Genus, Species.
Typology: a system of grouping, usually called types, which aid demostratin or inquiring by establishing a limited relationship among phenomena. A typology elicits a particular order depending on the purposes of the investigator and the phenomena so arranged.
To view in more detail: Linnaean system.
Indexes: Medlars, Shepard´s Citation (law), KWIC (Keyword in Context)
Facets is a more versatile scheme than the Dewey Decimal (usually the one libraries use).
I also found: "Owing to a classification error, the location identifier of that simple drawer containing all of recorded human knowledge was lost beyond recall" in a note about science fiction (Hal Draper "MS FND A LBRY".
Using Google I found :
"In Hal Draper's 'Ms Fnd in a Lbry' (1961, in Mowshowitz 1977) information technology is both the effect and the cause of the information explosion. New technology is used to reduce the volume of physical storage required for information sources. But this leads to an ever increasing need for bibliographies, indexes, indexes of indexes, bibliographies of bibliographies and so on. In the end errors lead to the complete collapse of the system."
(cutted and pasted from Imagining Futures, Dramatizing Fears by Daniel Chandler)
Amazing: this triggered my recollection of the Guide (Do not panic!) , a wonderful Douglas Adams creation (see h2g2, as well).