1. Copyright © 2002 Cycorp Why use logic? CycL Syntax Collections and Individuals (#$isa and #$genls) Microtheories Foundations of Knowledge Representation in Cyc

2. Copyright © 2002 Cycorp NL vs. Logic: Expressiveness NL: Jim’s injury resulted from his falling. Jim’s falling caused his injury. Jim’s injury was a consequence of his falling. Jim’s falling occurred before his injury. Logic: identify the common concepts, e.g. the relation: x caused y Write rules about the common concepts, e.g. x caused y  x temporally precedes y NL: Write the rule for every expression?

3. Copyright © 2002 Cycorp NL vs. Logic: Ambiguity and Precision x is running-InMotion  x is changing location x is running-DeviceOperating  x is operating x is running-AsCandidate  x is a candidate x is at the bank. river bank? financial institution? NL: Ambiguous Logic: Precise x is running. changing location? operating? a candidate for office? Reasoning: Figuring out what must be true, given what is known. Requires precision of meaning.

4. Copyright © 2002 Cycorp NL vs. Logic:Calculus of Meaning Logic: Well-understood operators enable reasoning: Logical constants: not, and, or, all, some Not (All men are taller than all women). All men are taller than 12”. Some women are taller than 12”. Not (All A are F than all B). All A are F than x. Some B are F than x.

5. Copyright © 2002 Cycorp Logic-Based Language vs. Other Formal Languages Logic –Mode-independent –KR and Indexing are independent –Implicit knowledge is preserved in the KB Frames & Slots, OO –Reasoning depends on mode (in-args, out-args) –Less reuse; either less coverage or more bulk and more work –KR must be designed around indexing –Implicit knowledge is code- dependent

6. Copyright © 2002 Cycorp carl animal_type: elephant mother: claire elephant order: mammal claire animal_type: elephant mother: elaine (isa Carl Elephant) (mother Carl Claire) (genls Elephant Mammal) Indexing and KR

7. Copyright © 2002 Cycorp elephant order: mammal *size: large *color: gray *height: *weight: (genls Elephant Mammal) (implies (and (isa ?X Elephant) (gender ?X Male) (height ?X (Meter ?Y))) (weight ?X (Ton (TimesFn ?Y 2)))) Implicit knowledge

8. Copyright © 2002 Cycorp Why use logic? –Expressiveness –Precision –Meaning –Use-neutral representation Indexing and KR Implicit knowledge Summary