SBVR_ — SBVR Issue - Restrictions on Variables

SBVR supports restrictions on variables introduced by quantifications, but does not support them on variables introduced by projections. The result is that projections fails to fully formulate meanings in some cases.

Consider the following two statements:

A receptionist at a hospital may decide what doctor employed by the hospital sees a given patient.

A receptionist at a hospital may decide what doctor is employed by the hospital and sees a given patient.

These two statements clearly have different meanings. In the first case, there is no stated permission for a reception to decide about who is employed by a hospital. The receptionist is permitted to decided from among doctors employed by the hospital which one sees a patient. But in the second, the permission to decide applies to the conjunction of a doctor being employed and seeing a patient (a decision not likely to be given to a receptionist).

The problem is that SBVR currently supports formulating only the second statement, not the first. An attempt to formulate the first ends up with the formulation of the second because SBVR does not support restrictions on variables introduced by projections. Formulations of both statements incorporate an answer formulation having a projection on a variable that ranges over the concept ‘doctor’. For the second statement, the projection is constrained by a conjunction of two atomic formulations based on ‘hospital employs person’ and ‘doctor sees patient’ respectively. For the first statement, the variable should be restricted by an atomic formulation based on ‘hospital employs person’ and the projection should be constrained by an atomic formulation based on (‘doctor sees patient’) showing that a receptionist’s decision is about what doctor sees the patient and the choice is restricted to doctors employed by the hospital. But SBVR does not allow the restriction on the variable because it is introduced by a projection.

In the original conceptualization of restrictions on variables, they were supported for all variables, but at that time it seemed that there was no need for restrictions on variables introduced by projections, so the “restricts” fact type was moved to ‘quantification’ so that it would only apply to variables introduced by quantifications. But now it is clear from examples that the “restricts” fact type needs to be moved from ‘quantification’ to ‘variable’ where it can be used for all sorts of variables.

Replace the fact type 'logical formulation restricts quantification' with 'logical formulation restricts variable'. Fix reference schemes, necessity statements and examples accordingly.