SBVR16 — SBVR ISSUE - definite description

Definite descriptions do not always define individual concepts

The entry for ‘definite description’ in SBVR 11.1.3 includes this structural rule:

Necessity: Each definite description is the definition of an individual concept.

The rule is incorrect. A definite description defining a concept in a schema might well be taken as defining an individual concept, but a definite description within a statement of a fact in a model need not define an individual concept because it need not identify the same individual in all possible worlds. It would identify an individual in the world described by the fact. Similarly, a definite description in the context of a rule statement might identify a single individual in each situation addressed by the rule, but not necessarily the same individual in all possible worlds. E.g., “the previous calendar month” definitely describes one month, but which month it describes depends on the current month, which can vary across possible worlds.

Also, a note should be added to the entry for “definite description” to point out that the one thing defined by a definite description can be a set (e.g., “the cars owned by EU-Rent”, which, by the way, is not the same set in all possible worlds).