H. W. Buff

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Zntroduction In his book (1) on the relational model ver-sion2, Codd defines a a-valued propositional logic with two different valuations for missing information, aissing-and-applicable~ and missing-and-irmpplicable. The truth tables are the following (+ is disjunction, ~ conjunction, N() negation): x I N(x) x÷y I t a I f xly I t a I f *1 f tltttt tltalf a(More)
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