Ontology
An ontology without a verb keeps every room locked
An ontology can name every object in a building and still be mute. The building starts to speak at the verb.
01
Corridors
The OWL 2 Primer, a W3C Recommendation of 11 December 2012, puts the interesting sentences in a specific place. Objects are individuals. Categories are classes. Relations are properties. An object property runs from one individual to another: this customer pays this order. A datatype property hangs a value on an individual, such as an age. "This is a customer" is a label on a door. "This customer pays this order" is someone walking through it.
Picture the floor. Rooms are the objects. Corridors are the links. A clerk walks only where a corridor was drawn. Two rooms that share a wall and have no door are neighbors on the plan and strangers in the work.
02
The spreadsheet is the door nobody filed
A company graph often contains a person and an invoice and no verb between them. The invoice knows an account number. The person knows an email. Someone keeps a sheet that says which email owns which account. That sheet is the relation the official ontology never wrote down. It is also the file that leaves when its author leaves.
A foreign key is a narrower thing than a verb. It says one row points at another row. It does not say whether the pointing means pays, owns, or replaced. A pointer without a verb is a string on a doorknob.
03
The morning test
More links do not make a better ontology. A link you cannot say out loud is a rumor with a column. The test fits in one morning. Watch which two objects a clerk actually moves between before lunch. If the ontology has no verb for that walk, the morning is happening outside the model, and the model will answer as if the morning did not happen.
On the record
The OWL 2 Web Ontology Language Primer (Second Edition) is a W3C Recommendation dated 11 December 2012. It defines object properties as relations between individuals, and datatype properties as relations between an individual and a data value.
W3C, OWL 2 Primer
A foreign key in a relational database constrains a pointer from one row to another. It does not, by itself, name what that pointer means.
Relational model, standard usage
The side spreadsheet next to an official ontology is often the missing verb, and it leaves with the person who maintains it. How fast that happens depends on that person.
Worked example, this magazine