Related Work

The references attached at the end of this document show some of the other work done on this subject. Just to give a feel for how close people’s thoughts were to Tuple-marks I include a few quotes:

David McGoveran

"...The lack of a value for a property should automatically imply an appropriate modification of the relation predicate."

C.J. Date

"To say that certain properties might not be held by certain of those entities is thus a contradiction in terms – it's to say that those entities aren't of that type after all!"

David McGoveran

"Furthermore, conditional operators would then be understood as operations on multiple relationships (masquerading as single relationships) and having a multiple entity result (again masquerading as a single entity)."

James R. Alexander

"...what my database "knows" and how it "knows" is clear: It knows only what it contains and what it contains, I put there.."

David McGoveran

"Whenever a value in a non-key base table column is optional (that is, the database designer permits it to be null), the column represents a conditional property or meaning criterion. Such columns indicate that multiple entity types are being represented in a single table. Each of these entities have distinct relation predicates"