Certainty factors and truth maintenance allow rules to deal with uncertainty. However, rules are cumbersome as a way of encoding relational knowledge and knowledge about objects. People have vast background knowledge to cope with everyday situations. We don't have to be told everything explicitly because we can call on the background knowledge. This is called common sense reasoning.
Semantic networks represent inheritance.
Sets of things in a semantic network are termed types . Individual objects in a semantic network are termed instances . John gives the book to Mary. Problems with Semantic Networks While semantic networks support default reasoning very well through the inheritance mechanism, they are not as flexible as logic when representing general statements. They add procedural attachment .