knowledge representation use of logic. artificial agents need knowledge and reasoning power can...
TRANSCRIPT
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Knowledge Representation
Use of logic
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Artificial agents
need Knowledge and reasoning power Can combine GK with current percepts Build up KB incrementally Logic primary vehicle K always definite ( T/F)
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Problem for a robot
If red light is ON or it is morning shift or supervisor absent then door is locked.
If door is locked it implies that the red light is turned ON or it is morning shift or the supervisor is absent
If load is small in size or load is light then the conveyor belt moves
If the conveyor belt is moving then it means the load has a small size or load is light
The Red light is off, the Conveyor belt is not moving and the Door is locked.
The robot wants to know if the load is heavy (not light).
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Robot needs a Knowledge Base and reasoning ability
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Knowledge base
Central component of a K based agent Set of sentences INFERENCE
– Deriving new info from old
Language to enable building KB
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Interpretations
Language semantics defines TRUTH of each sentence w.r.t. each possible world
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Similarity with CSP
Constraint solving is a form of Logical reasoning
Constraint languages: LOGICS
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Wff and logical reasoning
Entailment:– Sentence follows logically from another sentence
KB |= s iff in every model in which KB is true, s is
also true
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Inference algorithm
Enumerate the models Check if s is true in every model
(interpretation) for which KB is also true Backtracking search – recursively assign
values to variables Exponential complexity
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definitions
Validity Tautology Deduction theorem Satisfiability inconsistancy
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Reasoning patterns in Propositional logic
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Inference rules
Modus Ponens And Elimination Standard logical equivalances
– De Morgan– Contra positive– Distributive laws– Associative laws
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Deduction
With the knowledge base that the robot has, and what it currently perceives
(more knowledge added to the KB),
the robot wants to deduce that
the load is not light
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Knowledge that robot has
If red light is ON or it is morning shift or supervisor absent then door is locked.
If door is locked it implies that the red light is turned ON or it is morning shift or the supervisor is absent
If load is small in size or load is light then the conveyor belt moves
If the conveyor belt is moving then it means the load has a small size or load is light
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Observations by the robot
Red light is off Conveyor belt is not moving Door is locked
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What the robot wants to establish?
The load is not light
( or in other words it is heavy)
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Knowledge + Observation (K.B.)
If red light is ON or it is morning shift or supervisor absent then door is locked.
If door is locked it implies that the red light is turned ON or it is morning shift or the supervisor is absent
If load is small in size or load is light then the conveyor belt moves
If the conveyor belt is moving then it means the load has a small size or load is light
Red light is off Conveyor belt is not moving Door is locked
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Propositions
P: red light is ON M: it is morning shift N: supervisor absent D: door is locked. Q: load is small in size R: load is light B: the conveyor belt is moving
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Next?
Now generate wffs and start the inference process
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Steps to help the robot (inferencing)
Consider a relevant rule for conveyor belt Use And-elimination Use contra-positive relation Use modus ponens Use de morgan’s law
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PROOF?
PROOF: Sequence of application of Inference rules. Finding proofs is like finding solutions to search
problems. Successor function generates all possible application
of inference rules In worst case, search for proof would be as bad as
enumerating all the models Some irrelevant propositions can be ignored to
speed up search.
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Monotonicity
Set of entailed sentences can only increase as info is added to KB.
Rules can be applied wherever suitable
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Resolution
What about completeness? Can everything be inferred? Resolution rule forms basis for a family of
complete inference procedures.
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Refutation completeness
Resolution can be used to either
CONFIRM
or
REFUTE a sentence
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Artificial Intelligence
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Intelligent?
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What is intelligence?
computational part of the ability to achieve goals in the world