04/19/23 Formal Reasoning Group, Stanford University

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Representation of Actions in Cyc and KM

RKF PI Meeting

Thursday, October 18, 2001

Aarati Parmar

FRG Stanford

Pierluigi Miraglia

Cycorp

04/19/23 Formal Reasoning Group, Stanford University

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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

04/19/23 Formal Reasoning Group, Stanford University

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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

s’

s F

F

BaseKb/*Global

04/19/23 Formal Reasoning Group, Stanford University

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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))

sF a

s’

04/19/23 Formal Reasoning Group, Stanford University

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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.)

04/19/23 Formal Reasoning Group, Stanford University

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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)))

04/19/23 Formal Reasoning Group, Stanford University

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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.)

04/19/23 Formal Reasoning Group, Stanford University

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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?).

04/19/23 Formal Reasoning Group, Stanford University

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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

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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)

04/19/23 Formal Reasoning Group, Stanford University

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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.

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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.

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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.