Inheritence and Instances

• Inheritence and instances give representational efficiency.
• You don't need to store all the facts associated with each instance.
• Instead you can derive facts from inheritence.
• Tweety can fly.
• This is default reasoning.
• This is one of the great aspects of our own (human) knowledge.
• We might see a dog for the first time.
• However we already know a lot about it, because it is a member of a class.
• Or even better, we might have an idea about it.
• For example, dogs like bones, so Bonnie likes bones.
• However, inheritence can be overriden.
• Notice how penguins don't fly.
• If we find out Bonnie (or Labradors) don't like bones, we can override the inheritence.
• All you do is look up the inheritence hierarchy.
• Unlike FOPL, semantic nets are non-monotonic.