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Representation of Actions in Cyc and KM RKF PI Meeting Thursday, October 18, 2001

Representation of Actions in Cyc and KM RKF PI Meeting Thursday, October 18, 2001. Aarati Parmar FRG Stanford. Pierluigi Miraglia Cycorp. Representation of Actions in Cyc & KM.

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Representation of Actions in Cyc and KM RKF PI Meeting Thursday, October 18, 2001

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  1. Representation of Actions in Cyc and KM RKF PI MeetingThursday, October 18, 2001 Aarati Parmar FRG Stanford Pierluigi Miraglia Cycorp Formal Reasoning Group, Stanford University

  2. Representation of Actions in Cyc & KM • Cyc and KM (Component Library v1.0) are both logic-based ontologies with inheritance, and some non-monotonic reasoning. • Compare on: • Basic Temporal Formalism • Action Ontology • Reasoning about Change Formal Reasoning Group, Stanford University

  3. BaseKb/ *Global F s s’ Basic Temporal Formalism: States • Basic unit of state is implemented as a microtheory/context in both: • States are nested, so that facts from all super-states are visible • One unique super-situation (BaseKB/*Global) housingtimeless facts, visible to all situations. • Cyc's holdsIn and ist-Asserted corresponds to KM's holds-in, in-situation F Formal Reasoning Group, Stanford University

  4. F a s s’ Basic Temporal Formalism: States • KM uses situations of sitcalc (state space): • Cyc has two temporal formalisms: 1. “Davidsonian” framework • Action sentences are implicit existential assertions • Instances of Events (subclass of Situation-Temporal) have spatio-temporal extent • Slots and temporal relations (ActorSlots;startsAfterEndingOf) relate properties of actions 2. In development: • Assertions modified by temporal and modal operators • (possible-Historical (eats Fritz Caviar)) Formal Reasoning Group, Stanford University

  5. Basic Temporal Formalism: Actions • In both, actions are defined as events with a protagonist. • KM actions connect situations. • Has next-situation = result of sitcalc (can represent possible futures: • Actions can be composed of subactions, etc. • Future support for situation during the action. • Cyc actions more process-like, (instances of Event have temporal extent.) Formal Reasoning Group, Stanford University

  6. Action Ontology • Action properties inherited in both Cyc and KM through hierarchy • KM: • uses slots and values for arbitrary properties • more powerful than most frame-based languages as values can be evaluable expressions containing quantification and implication: • precondition list for Move: (if (has-value (the source of Self)) then (forall (the object of Self)) (:triple It location (the source of Self))) Formal Reasoning Group, Stanford University

  7. Action Ontology • Cyc: • properties formalized through Roles, ActorSlots other temporal relations • employs "skolem functions" to relate objects to actions, e.g. (relationAllExists buyer Buying IntelligentAgent) • how an action is done formalized throughperformanceLevel, rateofEvent • also categorizes different temporal objects (AccomplishmentType (actions that have a completion point), etc.) Formal Reasoning Group, Stanford University

  8. Reasoning about change: Preconditions • To do progression (regression), preconditions, as well as the result of an action need to be formalized. • KM uses STRIPS prec, add, delete lists to compute effects of actions. • Cyc has an expressively rich set of preconditions, but they are not uniformly used (what predicate do we query to see if action a executable?). Formal Reasoning Group, Stanford University

  9. Reasoning about change: Preconditions • Cyc preconditions represented through a multitude of predicates: • some ActorSlots are specific preconditions (inputs) • preconditionFor-{PropSit, Events, Props, SitProp} • (preSituation Event1 StaticSit2) a very weak kind of precondition • necessary conditions necConditionFor-Event and necConditionFor-Scene Formal Reasoning Group, Stanford University

  10. Reasoning about change: Results • KM: • STRIPS lists compute direct effect of actions • a simple form of non-monotonic reasoning used to compute the inertial effects • extra support for ramifications (non-inertial effects) Formal Reasoning Group, Stanford University

  11. Reasoning about change: Results • Cyc: • (postSituation Event1 StaticSituation2) : closest thing to result • causation between other/more general classes:eventOutcomes, causes-EventEvent, causes-SitProp, causes-ThingProp,causes-PropProp • looser notion of salience: postEvents and inReactionTo, and functions STIB, STIF. • Once again, a plethora of different levels of result used in Cyc, but no one used generally. Formal Reasoning Group, Stanford University

  12. Conclusions • Cyc has a rich ontology, but current formalism does not go the route of talking about the set of facts which change, like KM. • KM is better qualified to infer the results of actions, for this reason, as well as the non-monotonicity built into the system. • While Cyc can teach us much about actions and properties of them, KM can actually simulate these actions. Formal Reasoning Group, Stanford University

  13. Bibliography • Clark, P. and Porter, B. (1998). KM (v1.3): Users Manual. Knowledge-Based Systems Group, Univ. of Texas at Austin, Austin, Texas. • Cyc. http://www.cyc.com. • McCarthy, J. and Hayes, P. J. (1969). Some Philosophical Problems from the Standpoint of Artificial Intelligence. In Meltzer, B. and Michie, D., editors, Machine Intelligence 4,pages 463--502. Edinburgh University Press. Formal Reasoning Group, Stanford University

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