Advice for building expert systems: Precepts or proverbs?

Useful criteria for developing and implementing expert systems could provide essential information to guide practitioners in building successful systems. Many sources contain such criteria in a variety of forms, including summaries of the actions and precautions practitioners should take to produce successful systems. The advice, however is often contradictory and proverb-like. It provides little or no clarification of environmental context or supportive empirical evidence but exemplifies both precept and proverb.