intro_histoire_numerique:ontoclean

https://en.m.wikipedia.org/wiki/OntoClean
Rigidity: Rigid, Anti-Rigid and Semi-Rigid types (UFO-C on OntoUML)
N. Guarino/C. A. Welty, « An Overview of OntoClean », in Steffen Staab, ed., Handbook on ontologies, 2nd ed. Berlin: Springer, 2009.

Rigidity (time-indexed qualities or classifications)
- Essential properties define an entity throughout its life
- A ‘student’ : not a class but a time-indexed property of a person
Identity (terms and classes)
- map vs a sketch vs an information object of type ‘map’ or ‘sketch’
Unity (parthood)
- A crowd of humans vs a group having a plan
Dependence (one instance implies the existence of another one)
- No human without a brain, no human without a birth