Converse nonimplication


In logic, converse nonimplication is a logical connective which is the negation of converse implication.

Definition

Converse nonimplication is notated, or, and is logically equivalent to and.

Truth table

The truth table of.

Notation

Converse nonimplication is notated, which is the left arrow from converse implication, negated with a stroke.
Alternatives include

Properties

falsehood-preserving: The interpretation under which all variables are assigned a truth value of 'false' produces a truth value of 'false' as a result of converse nonimplication

Natural language

Grammatical

Example,
If it rains then I get wet, just because I am wet does not mean it is raining, in reality I went to a pool party with the co-ed staff, in my clothes and that is why I am facilitating this lecture in this state.

Rhetorical

Q does not imply P.

Colloquial

Not P, but Q.

Boolean algebra


Converse nonimplication in a general Boolean [algebra (structure)|Boolean algebra] is defined as.

Example of a 2-element Boolean algebra: the 2 elements with 0 as zero and 1 as unity element, operators as complement operator, as join operator and as meet operator, build the Boolean algebra of propositional logic.



Example of a 4-element Boolean algebra: the 4 divisors of 6 with 1 as zero and 6 as unity element, operators as complement operator, as join operator and as meet operator, build a Boolean algebra.


Properties

Non-associative

if and only if #s5. Hence in a nontrivial Boolean algebra converse nonimplication is nonassociative.
Clearly, it is associative if and only if.

Non-commutative

  • if and only if #s6. Hence converse nonimplication is noncommutative.

Neutral and absorbing elements






Computer science

An example for converse nonimplication in computer science can be found when performing a right outer join on a set of tables from a database, if records not matching the join-condition from the "left" table are being excluded.