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From: R. Nachmani
Subject: Three-valued logic
Date: 25 Kislev 5784
This is the classic null comparison problem. In database systems, NULL compared to anything — including NULL — returns unknown. You cannot query for NULL using equality.
We would need a separate operator: "is unstated" versus "is negative."
Actually, this is exactly how SQL works. You use IS NULL, not = NULL. The specification's three-valued logic maps directly to SQL semantics.
We have designed a time assertion format that is, accidentally, a relational database column.
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