Ontology
An ontology can invent a customer by naming one
An ontology is a short list with a long shadow. It decides which things are allowed to exist, and which words are only weather.
01
The list that hires a person
In June 1993 Thomas R. Gruber described an ontology as the specification of a vocabulary a shared domain is allowed to use: the classes, the relations, the functions, and the other objects that domain is willing to name. The dryness is how the sentence travels. A picture in one head cannot be shipped. A specification can.
A counter can run on four names: customer, order, burger, and payment. The moment the list also says complaint, the counter grows a door for the person who is unhappy. Leave that name out and the same person is a customer who has not paid. The ontology did the hiring. The till only followed.
02
A tree of nouns is a filing cabinet
Nicola Guarino, at the 1998 Formal Ontology in Information Systems meeting in Trento, pressed a split that still earns its place. Plenty of files called an ontology are a tree of nouns. A tree tells you that a burger is a kind of food. It does not tell you that a customer may order one, or that an order may close. Without those permissions you have a menu. The world where people act is missing.
Barry Smith, in his chapter for Floridi's Blackwell Guide (2004), splits the word itself. Ontology, the philosophical kind, asks what exists. An ontology, the countable kind, is an artifact a team maintains so their records stop arguing with each other. A company slide that says "our ontology" is usually asking for the second and borrowing the prestige of the first.
03
One name, or the join fails
Call a refund a gesture at the counter and a reversal in the ledger. For a quiet week the two words live apart. Then a report asks how many gestures became reversals. The join returns nothing, because the two systems never agreed the event was the same event. The repair is one name, used in both rooms.
On the record
Thomas R. Gruber, "A Translation Approach to Portable Ontology Specifications", Knowledge Acquisition 5(2), June 1993, pages 199-220. An ontology there is a specification of the shared vocabulary: classes, relations, functions, and other objects.
Knowledge Acquisition, Elsevier, 1993
Nicola Guarino, "Formal Ontology and Information Systems", opening paper of the 1998 Formal Ontology in Information Systems conference in Trento. He separates a bare taxonomy from an ontology that also states what its terms are allowed to do.
FOIS 1998, Trento
Barry Smith, "Ontology", chapter 11 of Luciano Floridi (ed.), The Blackwell Guide to the Philosophy of Computing and Information, Blackwell, 2004. He keeps the philosophical question of what exists apart from the artifact an information system maintains.
Blackwell, 2004
Two names for one event make the first report that asks for both of them fail. The failure is the missing agreement. The calendar for that failure depends on when someone asks.
Worked example, this magazine