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Dec 12, 2022 •177 likes •275 views

Semantics Networks When you only have one relation, prop , it can be omitted without loss of information. Write prop ( Obj , Att , Value ) as Obj Att Val An Example Semantic Network building comp_sci lemon_laptop_10000 r107

  1. Semantics Networks When you only have one relation, prop , it can be omitted without loss of information. Write prop ( Obj , Att , Value ) as Obj Att Val ☞ ☞

  2. An Example Semantic Network building comp_sci lemon_laptop_10000 r107 building r117 ming lemon_computer room room model craig deliver_to brand owned_by logo comp_2347 lemon_disc packing color weight size cardboard_box light brown medium ☞ ☞ ☞

  3. Equivalent Logic Program prop ( comp _2347 , owned _ by , craig ). prop ( comp _2347 , deliver _ to , ming ). prop ( comp _2347 , model , lemon _ laptop _10000 ). prop ( comp _2347 , brand , lemon _ computer ). prop ( comp _2347 , logo , lemon _ disc ). prop ( comp _2347 , color , brown ). prop ( craig , room , r 107 ). prop ( r 107 , building , comp _ sci ). . . . ☞ ☞ ☞

  4. Frames The properties and values for a single object can be grouped together into a frame. We can write this as a list of attribute = value or slot = filler . [ owned _ by = craig , deliver _ to = ming , model = lemon _ laptop _10000 , brand = lemon _ computer , logo = lemon _ disc , color = brown , · · ·] ☞ ☞ ☞

  5. Primitive versus Derived Relations Primitive knowledge is that which is defined explicitly by facts. Derived knowledge is knowledge defined by rules. Example: All lemon laptops may have have size = medium . Associate this property with the class, not the individual. Allow a special attribute is _ a between an individual and a class or between two classes that allows for property inheritance . ☞ ☞ ☞

  6. A Structured Semantic Network room r117 ming cardboard_box building deliver_to packing computer comp_sci is_a building lemon_computer logo color r107 is_a brown lemon_disc lemon_laptop_10000 room size weight is_a medium craig light comp_2347 owned_by ☞ ☞ ☞

  7. Logic of Property Inheritance p An arc → n from a class c means every individual in the − class has value n of attribute p : prop ( Obj , p , n ) ← prop ( Obj , is _ a , c ). Example: prop ( X , weight , light ) ← prop ( X , is _ a , lemon _ laptop _10000 ). prop ( X , is _ a , lemon _ computer ) ← prop ( X , is _ a , lemon _ laptop _10000 ). ☞ ☞ ☞

  8. Choosing Primitive and Derived Relations ➤ Associate an attribute value with the most general class with that attribute value. ➤ Don’t associate contingent properties of a class with the class. ➤ Axiomatize in the causal direction. You want knowledge that is stable as the world changes. ☞ ☞

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