Not

not expr

Logical NOT. Returns True if expr is False, False if expr is True, or null.

And

expr1 and expr2

Logical AND. Returns True if both operands are True, False if either operand is False, or null.

Eqv

expr1 eqv expr2

Logical Equivalence. Returns True if both operands are True or both operands are False. Returns null if either operand is null, or returns False.

Or

expr1 or expr2

Logical OR. Returns False if both operands are False, True if either operand is True, or null.

Xor

expr1 xor expr2

Exclusive OR. Returns False if both operands are True or both operands False. Returns True if one operand is True and one False, or returns null.

Imp

expr1 imp expr2

Implication. Returns True if expr1 is False or expr2 is True, False if expr1 is True and expr2 is False, or null.