Research in Knowledge Representation and Reasoning

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Research inKnowledge Representationand Reasoning

• Stuart C. Shapiro
• Department of Computer Science Engineering
• Center for MultiSource Information Fusion
• Center for Cognitive Science
• University at Buffalo, The State University of
  New York

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MGLAIR Agent Architecture
Mind
KL (SNePS)
Independent of lower-body implementation
Body
PMLa
PMLb
Dependent on lower-body implementation
I/P s o c k e t s
PMLc
Proprioception
Speech
W O R L D
Hearing
SAL
Vision
Motion
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SNePS

• SNePS is a
• Logic-Based
• Frame-Based
• Network-Based
• knowledge representation, reasoning, and acting
  system.

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SNePS Is Logic-Based

• wff1! all(x)(Isa(x,dog) Property(x,four-leg
  ged))
• wff2! Isa(Toto,dog)
• Property(Toto,?x)?
• wff3! Property(Toto,four-legged)
• Isa(Fala,dog)!
• wff6! Property(Fala,four-legged)
• wff5! Isa(Fala,dog)
• askwh Property(?x,four-legged)
• Fala Fala
• Toto Toto
• list-wffs
• wff6! Property(Fala,four-legged)
• wff5! Isa(Fala,dog)
• wff3! Property(Toto,four-legged)
• wff2! Isa(Toto,dog)

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SNePS Is Frame-Based

• (describe nodes)
• (m6! (a1 Fala) (a2 four-legged) (r Property))
• (m5! (a1 Fala) (a2 dog) (r Isa))
• (m3! (a1 Toto) (a2 four-legged) (r Property))
• (m2! (a1 Toto) (a2 dog) (r Isa))
• (m1! (forall v1) (ant (p1 (a1 v1) (a2 dog) (r
  Isa)))
• (cq (p2 (a1 v1) (a2
  four-legged) (r Property))))
• (describe (assert r Isa
• a1 (Fido Rover Lassie)
• a2 (dog pet)))
• (m7! (a1 Lassie Rover Fido) (a2 pet dog) (r Isa))
• wff7! Isa(Lassie,Rover,Fido,pet,dog)
• Property(Rover, ?x)?
• wff8! Property(Rover,four-legged)

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SNePS Is Network-Based

• define-frame Ako(nil subclass superclass)
• Ako(x1, x2) will be represented by x1,
• Ako(man, dog, mammal).
• wff1! Ako(dog,man,mammal)
• Ako(mammal, fish, vertebrate).
• wff2! Ako(fish,mammal,vertebrate)
• Ako(vertebrate, animal).
• wff3! Ako(vertebrate,animal)
• (define-path subclass
• (compose subclass
• (kstar (compose superclass- ! subclass))))
• ...
• askwh Ako(?x, animal)
• vertebrate vertebrate

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Procedural Attachment

• A predicate or function symbol
• may be attached to a user-written procedure
• so instances may be computed
• in the underlying programming language.

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Example of Procedural Attachment

• Diff(7,3,?x)?
• wff24! Diff(7,3,4)
• Diff(10,?x,7)?
• wff25! Diff(10,3,7)
• Diff(?x,5,7)?
• wff26! Diff(12,5,7)
• Diff(15,8,7)?
• wff314! Diff(15,8,7)
• Diff(15,8,9)?
• wff316! Diff(15,8,9)

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Building Domain

• all(x)(onFloor(x)
• ( location(belowGround)),
• ( location(aboveGround))).

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Primitive Acts

• A version of procedural attachment
• for implementing intelligent agents
• perform say(Welcome, "to you all.")
• Welcome to you all.

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Policies

• Connect propositions and acts
• wheneverdo(location(belowGround),
• withsome(f, onFloor(f),
• say("It's dark here
  on floor",f),
• say("Where
  am I?",""))).
• wheneverdo(location(aboveGround),
• withsome(f, onFloor(f),
• say("It's sunny
  outside floor",f),
• say("Where
  am I?",""))).

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SNeBRBelief Revision/Assumption-Based Truth
Maintenance

• Identify possible culprits of contradictions.
• Disbelieve implications of disbelieved
  hypotheses.
• Use state constraints to adjust beliefs
• andor(1,1)onFloor(1),onFloor(2),onFloor(3),onFlo
  or(4).
• andor(1,1)location(belowGround),location(aboveGr
  ound).

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Combined Use ofSNeBR Procedural Attachment

• perform believe(onFloor(1))
• It's dark here on floor 1
• location(?x)?
• wff24! location(aboveGround)
• wff6! location(belowGround)
• perform believe(onFloor(4))
• It's sunny outside floor 4
• location(?x)?
• wff33! location(belowGround)
• wff7! location(aboveGround)

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BR with Multiple Sources

• wff1 all(x)(andor(0,1)mammal(x),fish(x))
• wff2 all(x)(fish(x) has(x,scales))
• wff4 all(x)(whale(x) fish(x))
• wff5 Source(Melville,all(x)(whale(x)
  fish(x)))
• wff6 all(x)(whale(x) mammal(x))
• wff7 Source(Darwin,all(x)(whale(x)
  mammal(x)))
• wff8 Sgreater(Darwin,Melville)
• wff11 free(Willy) and whale(Willy)

Note Source Sgreater props are regular
object-language props.
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Finding the Contradiction

• has(Willy, scales)?I infer fish(Willy)
• I infer has(Willy,scales)I infer
  mammal(Willy)I infer it is not the case that
  wff14 fish(Willy)

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Using Source Credibility

• A contradiction was detected within context
  default-defaultct.
• The contradiction involves the newly derived
  proposition wff17 fish(Willy)
  
• and the previously existing proposition
  wff14 fish(Willy)
• The least believed hypothesis (wff4)
  
• The most common hypothesis (nil)
• The hypothesis supporting the fewest wffs (wff1)
  
• I removed the following belief wff4
  all(x)(whale(x) fish(x))
• I no longer believe the following 2
  propositions wff14 fish(Willy) wff13
  has(Willy,scales)

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Conclusions

• MGLAIR is an agent architecture
• For connecting reasoning with sensing and acting
• SNePS is a
• Logic-based
• Frame-based
• Network-based
• Knowledge representation, reasoning, and acting
  system.
• Procedural attachment provides
• Sensing, acting, computing at the subcognitive
  layers
• SNeBR does belief revision truth maintenance.
• Source meta-knowledge may be entered and used.