SBVR11 — Clarify difference between EXISTS and OCCURS

Summary: SBVR makes an important distinction between the meanings of the word “exists” (existential quantification) and the word “occurs” (used to describe a state of affairs). A state of affairs can exist and thereby be involved in other things (e.g., plans, desires, fears, expectations) even if it does not occur, even if it never occurs. SBVR should explicitly define and explain the characteristic ‘state of affairs occurs’, and should then use that characteristic to define ‘actuality’.

Note that this issue is related to issue 14849 and became important in discussing 14849, but its resolution should be independent of 14849.

1. Add a new characteristic, ‘state of affairs is actual’ and use it to define ‘actuality’ (“is actual” is taken as a preferred alternative to “occurs”).
2. Explain the difference between ‘is actual’ and ‘exists’.