Part I

Types and Relations

Several of the entries appearing in this part of the dictionary—primarily ones having to do with type theory—are expanded or elaborated on in Part II (“Inheritance”). Such entries are marked “Without inheritance” in what follows (and the corresponding expanded entries in Part II are marked “With inheritance” accordingly).


0-adic (Of an operator or predicate) Niladic. Contrast 0-ary.

0-ary (Of a heading, key, tuple, relation, etc.) Of degree zero. Contrast 0-adic.

0-place (Of a predicate) Niladic.

0-tuple The empty tuple; the tuple of degree zero.

1NF First normal form.

2NF Second normal form.

2VL Two-valued logic.

3NF Third normal form.

3VL Three-valued logic.

4NF Fourth normal form.

4VL Four-valued logic.

5NF Fifth normal form.

6NF Sixth normal form.


A A relationally complete (q.v.), “reduced instruction set” version of relational algebra with just two primitive operators—REMOVE (essentially projection on all attributes but one), q.v., and an algebraic analog of either NOR or NAND, q.v. The name A (note the boldface) is a doubly recursive acronym: It stands for ALGEBRA, which in turn stands for A Logical Genesis Explains Basic Relational Algebra. As this expanded name suggests, the algebra A is designed in such a way as to emphasize its close relationship ...

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