Lecture-8

Lecture-8 - Artificial Intelligence CS 165A 165A Thursday,...

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Artificial Intelligence S 165A CS 165A Thursday, Jan 27, 2011 nowledge and reasoning (Ch 7 Knowledge and reasoning (Ch. 7) 1
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Notes • HW#2 due next Tuesday P specification will be out tomorrow (Jeff is working on MP specification will be out tomorrow (Jeff is working on details, you will have enough time) 2
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Reminder: Three parts of an AI Program? • AI programs can generally be thought of as comprising three separated parts – Data / knowledge (“knowledge base”) – Operations / rules (“production rules”) ontrol – Control • What are these three parts in M&C, TTT, vacuum world? e need to consider how to represent knowledge and how We need to consider how to represent knowledge and how to reason about what we know (with respect to what we want) – More high-level and flexible representations and reasoning abilities 3
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The Wumpus World 4
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Knowledge and reasoning • We want more powerful methods for –R e presenting Knowledge –more general methods for representing facts about the world and how to act in world – Carrying out Reasoning – more general methods for deducing additional information and a course of action to achieve goals – Focus on knowledge and reasoning rather than states and search Note that search is still critical • This brings us to the idea of logic 5
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Logic – the basis of reasoning Logics are formal languages for representing information such that conclusions can be drawn – I.e., to support reasoning Syntax defines the sentences in the language llowable symbols Allowable symbols – Rules for constructing grammatically correct sentences Semantics defines the meaning of sentences – Correspondence (isomorphism) between sentences and facts in the world – Gives an interpretation to the sentence – Sentences can be true or false with respect to the semantics Proof theory specifies the reasoning steps that are sound (the inference procedure) 6 6
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Knowledge-based agents •A knowledge-based agent uses reasoning based on prior and acquired knowledge in order to achieve its goals • Two important components: – Knowledge Base (KB) epresents facts about the world (the agent’s environment) Represents facts about the world (the agent s environment) – Fact = “sentence” in a particular knowledge representation language (KRL) B = set of sentences in the KRL KB set of sentences in the KRL – Inference Engine – determines what follows from the knowledge base (what the knowledge base entails ) f /dd t i Inference / deduction – Process for deriving new sentences from old ones Sound reasoning from facts to conclusions 7
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Knowledge base (KB) for agents • The KB agent must be able to – Represent states, actions, etc. – Incorporate new percepts – Update the internal representation of the world – Deduce hidden properties of the world – Deduce appropriate actions, given the goals an be viewed at different levels of explanation Can be viewed at different levels of explanation Knowledge level Abstract. What does the agent know?
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This note was uploaded on 02/22/2011 for the course CS 165A taught by Professor Su during the Spring '11 term at UCSB.

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Lecture-8 - Artificial Intelligence CS 165A 165A Thursday,...

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