How Good are KR Formalisms

• Knowledge Representation formalisms all are incomplete.
• They don't represent the world perfectly.
• We're not exactly sure how people represent knowledge, but it is certain that each person's knowledge is incorrect and incomplete (small brain, big world).
• What do each of the KR formalisms help us do?
• Logic has very little semantics. It doesn't know what Taller means. I might as well say Gern(x,Chris) or Gern(x,Ferb). (This is a classic problem known as the symbol grounding problem.)
• Logic was designed to formalise reasoning. It intentionally removes semantics.
• Symbols can be dangerous. The things that we talk about in this class are purely symbolic, therefore they have no natural semantics.
• Different KR techniques are going to be better for different applications.
• One obvious distinction is between declarative and procedural knowledge.
• Declarative knowledge is smaller but faster.
• Procedural knowledge is bigger but slower.
• For example, it's faster to store 11x11=121 than to caluclate it, but you have to store a lot of information to do the 12x12 multiplication table.