Inheritence, semantic nets, frames and XML

• Inheritence (hierarchy) is a central organising principle that supports an enormous amount of reasoning.
• You might know it as subclassing in Object Oriented Programming.
• The basic idea is that if you know A is-a B, and you know a fact about B, you know a fact about A. In OOP, you only have to encode extra stuff for the sublass (A).
• Semantic nets make extensive use of this. Semantic nets were developed as a means of describing how people represent knowledge.
• Semantic nets are a graph structure, with nodes being classes or instances.
• They are connected by arcs that represent relations. The most important is is-a, though instance-of and part-of are also important.
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• Go back to the Clips lab, and try to implement the semantic net.
• Frames are just semantic nets with particular slots specified; they have more structure.
• XML uses semantic nets.
• Most modern KR languages (e.g. LOOM and KL-One) are semantic nets.
• Ontologies
• Cognitive maps are closely related.