After reviewing many definitions I ran across these terms which I will paraphrase from Wikitionary. I believe this phrase to be a very accurate statement.
AI is “an exhibition of an artificial (non-natural, man-made) entity dealing with the reproduction or mimicking of human-level thought in a manner similar to or on the same general level as a human being.”
In short, an intelligent system is one that learns during its existence. It learns, for each situation, which response permits it to reach its objectives. It continually acts, mentally and externally, and by acting reaches its objectives more often than pure chance would indicate. As an intelligent system exhibits human-level adaptation, it becomes apparent that the rule-based AI grows as the entity becomes aware of feedback and adapts to the information gained to create new rules similar to an expert system.
As experts gain insight navigating new situations, the rules are formed to correctly build a path for reaching objectives. This ‘knowledge base’ becomes the bottom line for most AI programming. In all the examples above it would seem that all deal with rules but some are proactive at creating reactions and learning and others that are reactive to previous systems.