Logic puzzle might be present in lieu of a grid in a puzzle about the location of different shops. Logic puzzle A logic puzzle is a puzzle deriving from the mathematics field of deduction. The logic puzzle was first produced by Charles Lutwidge Dodgson, who is better known under his pen name Lewis Carroll, the author of "Alice's Adventures in Wonderland". In his book "The Game of Logic" he introduced a game to solve problems such as confirming the conclusion "Some greyhounds are not fat" from the statements "No fat creatures run well" and "Some greyhounds run well". Puzzles like this, where
Inference engine modes either special rule or facts: forward chaining and backward chaining. Forward chaining starts with the known facts and asserts new facts. Backward chaining starts with goals, and works backward to determine what facts must be asserted so that the goals can be achieved. The logic that an inference engine uses is typically represented as IF-THEN rules. The general format of such rules is IF <nowiki><logical expression></nowiki> THEN <nowiki><logical expression></nowiki>. Prior to the development of expert systems and inference engines artificial intelligence researchers focused on more powerful theorem prover environments that offered much fuller implementations of First Order Logic. For