SBVR11 — Definition of proposition

SBVR clause 8.1.2 defines 'proposition' as 'meaning that is true or false'.
The Date/Time specification, and some SBVR examples, show that some propositions are used for their "content" – the situation that the proposition describes – without regard to their truth value. For example, "Each rental car must be inspected before it is available for rental" uses the proposition 'rental car r is inspected' (for each referent of r) to refer to situation in which the car is inspected, and the proposition 'rental car r is available for rental' to refer to the situation in which the car can be rented. The rule relates these situations without requiring any true/false evaluation of either of them. Further, the situation in which a given rental car is available is only sometimes an actuality; the proposition 'r is available for rental' can be sometimes true and sometimes false in the actual world.
Thus, being true or false is not the most important characteristic of a proposition, and may not be well-defined.

Recommendation: 'proposition' should be defined as: conceptualization of an event, activity, situation or circumstance. Such a definition would be consistent with the idea that it 'corresponds to' a 'state of affairs'. It is also consistent with the idea that true and false are defined in terms of correspondence to an actuality. Those properties would be dependent on the situation that is identified in the proposed definition. This change of definition does not change the intent of the term 'proposition' in any way. It just avoids having the concept depend on having a truth value in usages that don't care. (It may be that the proposed definition needs some additional characteristic to distinguish it from a noun concept that corresponds to events, like 'heart attack'. For example, the proposition must be based on one or more fact types and involve things in fact type roles.)

Define ‘proposition’ more clearly while remaining consistent with the existing concept and structural rules. Add a note pointing out that a proposition is true or false regardless of whether its truth value is known or of interest. Modify the definitions of “is true” and “is false” to be consistent with the definition of proposition. Also, add a note that a proposition is true or false independently of whether the state of affairs to which it corresponds has been or will be actual.
Add “a statement of the proposition” as a reference scheme to ‘proposition’, as there is currently no way to identify a proposition except by creating a semantic formulation of it, and the natural language statement is the most people-oriented way to do it.