In expert systems or knowledge bases having an inference engine, forward inference is inference that occurs automatically as a result of adding new facts to the system. For example, if a system had a rule stating that every raven is black, and as soon as the system found out that Joe is a raven, it inferred that he is black in color, that would be forward inference. A terse way of explaining forward inference is that it is inference that happens at assert time.

Some systems treat all their inference rules as forward, while others allow specific rules to be tagged as such.

Contrast forward inference with backward inference, which is inference that happens at query time.