1. Lecture 7-2CS250: Intro to AI/Lisp Building Knowledge Bases Lecture 7-2 February 18 th, 1999 CS250

2. Lecture 7-2CS250: Intro to AI/Lisp Representational Adequacy Metaphysical adequacy Could the world have the representational form suggested without a contradicting the facts of the aspect of the reality we’re interested in? Epistemological adequacy Express facts about the world in a practical way Heuristic adequacy Are the reasoning processes used in solving a problem expressible?

3. Lecture 7-2CS250: Intro to AI/Lisp General Ontologies Categories Measures Composite Objects Time, Space and Change Events and Processes Physical Objects Substances Mental Objects and Beliefs

4. Lecture 7-2CS250: Intro to AI/Lisp Composite Objects Not inheritance –Difference between subclass and member General event descriptions –Schema –Script

5. Lecture 7-2CS250: Intro to AI/Lisp Using Events to Represent Change What’s the problem? –Continuous time –Multiple agents –Actions of different durations Event calculus - Reify events

6. Lecture 7-2CS250: Intro to AI/Lisp Event Calculus Vocabulary Events are splotches in the space-time continuum Events have subevents Some events are intervals

7. Lecture 7-2CS250: Intro to AI/Lisp Examples Suppose we wish to represent facts about market manias  f f  BulbEating  SubEvent(f,TulipMania)  PartOf(Location(f), Holland)  s s  StockFrenzy  SubEvent(s,USBullMarket)  PartOf(Location(f), ??)  s s  StockFrenzy  SubEvent(s,USBullMarket)  TradedOn(Exchange(s), NASDAQ)

8. Lecture 7-2CS250: Intro to AI/Lisp Place How are places like intervals? Relation In holds among places Location function: Maps an object to the smallest place that contains it

9. Lecture 7-2CS250: Intro to AI/Lisp Processes Why do we need processes when we have events? How can we say: –Barry Sonnenfeld was flying some time yesterday –Barry was flying all day yesterday Kurt D. Fenstermacher: Sonnenfeld directed: Men in Black (1997) Get Shorty (1995) The Addams Family (1991) Kurt D. Fenstermacher: Sonnenfeld directed: Men in Black (1997) Get Shorty (1995) The Addams Family (1991) E(Flying(Barry), Yesterday) T(Flying(Barry), Yesterday)

10. Lecture 7-2CS250: Intro to AI/Lisp A Logical Blender Suppose Bill is accused of killing a zucchini, and when the cold, but efficient, Detective Frigerator (known to his pals as simply “Re”) questions the orange juice pitcher in FOPL, the orange juice has no idea how to say: “Bill was in the kitchen with the tomato all day yesterday”

11. Lecture 7-2CS250: Intro to AI/Lisp Composite Events Use And to combine two events with the usual semantics: And isn’t so bad, but disjunction is a bit more complicated -- how do we say: “I saw the whole thing, the beef or the broccoli stabbed the zucchini all afternoon.”  p,q,e T(And(p, q), e)  T(p, e)  T(q, e)

12. Lecture 7-2CS250: Intro to AI/Lisp Time & Intervals Time is pretty important –Divvy up time into: Moments and ExtendedIntervals –Define a couple handy functions Start End Time Date

13. Lecture 7-2CS250: Intro to AI/Lisp When Intervals Get Together Meet Before After During Overlap

14. Lecture 7-2CS250: Intro to AI/Lisp Objects in the Space-Time Continuum Remember that events are splotches of space-time Some events have coherence through time Need to capture the idea of an object existing through time

15. Lecture 7-2CS250: Intro to AI/Lisp Roman Empire Roman Empire spread across much of Eurasia, expanding and contracting, from 753 B.C. until the 5th century A.D.

16. Lecture 7-2CS250: Intro to AI/Lisp Roman Empire at 218 B.C.

17. Lecture 7-2CS250: Intro to AI/Lisp Roman Empire at 117 A.D.

18. Lecture 7-2CS250: Intro to AI/Lisp Roman Empire at 395 A.D.

19. Lecture 7-2CS250: Intro to AI/Lisp Fluents Roman Empire is an event –Subevents include First, Second and Third Punic Wars One of the first known hammer and anvil movements in battle (216 BC @ Cannae) A fluent allows us to capture the notion of the Roman Empire throughout time T(Male(Emperor(RomanEmpire)), 1stCenturyAD) T(In(Gaul, Roman Empire), AD12)

20. Lecture 7-2CS250: Intro to AI/Lisp Fluent Flavors Fluent is a function, f:Situations Fvalues –Domain is the set of all situations (states of the world) If Fvalues is {TRUE, FALSE} then it’s a Propositional fluent If Fvalues is {All situations} then it’s a Situational fluent

21. Lecture 7-2CS250: Intro to AI/Lisp Substances Less vs. fewer Intrinsic vs. extrinsic properties Substances are those things that are fungible

22. Lecture 7-2CS250: Intro to AI/Lisp Going, Like, Totally Mental What are other agents know, and what are they thinking? –“Everybody’s looking at me” –“They’re trying to kill me” –“You look like someone who knows where I can find extra virgin olive oil” Start with a Believes predicate Believes(Agent, x)

23. Lecture 7-2CS250: Intro to AI/Lisp Reification & You A good first pass: Treat Flies(Superman) as a propositional fluent –Relationships like Believes, Know and When between agents and propositions are propositional attitudes The problem: Can Clark fly? Believes(Agent, Flies(Superman))

24. Lecture 7-2CS250: Intro to AI/Lisp “It is clear.” Referential transparency –Any term can be substituted for an equal term –FOL is referentially transparent

25. Lecture 7-2CS250: Intro to AI/Lisp Knowing for Action Knowing preconditions: What do you need to know to do action a? Knowledge effects: What effect does performing action a have on an agent’s knowledge?

26. Lecture 7-2CS250: Intro to AI/Lisp Replacing that Zucchini Grocery shopping –Percepts –Actions –Goals –Environment