SBVR15 — SBVR Issue: Problematic necessity in 8.5.2

In SBVR clause 8.5.2, the following Necessity appears:

Necessity: If a concept[sub]1 is coextensive with a concept[sub]2 then the extension of the concept[sub]1 is the extension of the concept[sub]2.

(where [sub] is used to show subscripts).

There are three problems with this Necessity:

1. This Necessity just restates the definition of ‘concept is coextensive with concept’ in 8.1.1.1. It adds nothing.

2. It is the only occurrence in SBVR v1.1 of the use of a subscript outside of a placeholder term, and that use is not defined in Annex C.

3. The meaning of the article ‘a’ before concept (1) and concept (2) is universal in this case, not existential, which contradicts Annex C.

Delete it!

Delete the Necessity that duplicates the definition, adding nothing to it

(see attached Issue disposition document)