Chapter 13Chapter 13

Artificial IntelligenceArtificial Intelligence

IntroductionIntroduction

Artificial Artificial intelligence (AI) is intelligence (AI) is the part of the part of computer science computer science that attempts to that attempts to make computers make computers act like human act like human beings.beings.

Turing test: Turing test:

A Division of LaborA Division of Labor

Three categories of tasks:Three categories of tasks:• Computational tasks:Computational tasks:

Adding numbers, sorting, searchingAdding numbers, sorting, searching Calculating the trajectory for the space shuttleCalculating the trajectory for the space shuttle

• Recognition tasks:Recognition tasks: Recognizing your best friendRecognizing your best friend Understanding the spoken wordUnderstanding the spoken word

• Reasoning tasks:Reasoning tasks: Planning what to wear todayPlanning what to wear today Deciding company’s strategic directionsDeciding company’s strategic directions

Human and Computer CapabilitiesHuman and Computer Capabilities

Knowledge Representation MethodsKnowledge Representation Methods

Natural languageNatural language Formal languageFormal language PictorialPictorial Graphical: e.g., semantic net Graphical: e.g., semantic net

RequirementsRequirements

Adequacy: the representation method mAdequacy: the representation method must be adequate to capture all of the relevust be adequate to capture all of the relevant knowledge.ant knowledge.

Efficiency: we want the representation forEfficiency: we want the representation form to be minimalist.m to be minimalist.

ExtendabilityExtendability Appropriateness Appropriateness

Recognition TasksRecognition Tasks

Connectionist architecture: formed by Connectionist architecture: formed by large number of simple “processors” large number of simple “processors” (neurons) with multiple interconnections.(neurons) with multiple interconnections.

A neuron:A neuron:

Artificial Neural NetworksArtificial Neural Networks

Simulate the connectionist architecture of huSimulate the connectionist architecture of human brainman brain

Applied to recognition taskApplied to recognition task A neural network for comparing two characterA neural network for comparing two character

ss What happens when two As are presented?What happens when two As are presented? One A and one Y?One A and one Y? PerceptronsPerceptrons Back-propagation Back-propagation

algorithmalgorithm

Reasoning TasksReasoning Tasks

Intelligent searchingIntelligent searching• Decision tree for sequential searchDecision tree for sequential search• Decision tree for binary searchDecision tree for binary search

Best-first searchBest-first search Means-end analysisMeans-end analysis Search the Internet: spiderSearch the Internet: spider

Intelligent AgentIntelligent Agent

A software technology designed to interA software technology designed to interact collaboratively with a user somewhaact collaboratively with a user somewhat in the mode of a personal assistant.t in the mode of a personal assistant.

Examples:Examples:• Desktop office software Desktop office software Office Office 小幫手小幫手• Personalized Web search enginePersonalized Web search engine• Buying and selling agentsBuying and selling agents• Electronic travel agents Electronic travel agents

Expert SystemsExpert Systems

Rule-based systemsRule-based systems Knowledge-based systemsKnowledge-based systems Contains two components:Contains two components:

• A knowledge baseA knowledge base: a set of facts about : a set of facts about the subject matterthe subject matter

• An inference engineAn inference engine: a mechanism for : a mechanism for selecting the relevant facts and for selecting the relevant facts and for reasoning from them in a logical wayreasoning from them in a logical way

The Reasoning ProcessThe Reasoning Process

Modus ponens: method of assertionModus ponens: method of assertion Inference engines for rule-based system can prInference engines for rule-based system can pr

oceed in:oceed in:• Forwarding chaining: begins with assertions and triForwarding chaining: begins with assertions and tri

es to match those assertions to the “if” clauses of es to match those assertions to the “if” clauses of rules, thereby generating new assertions.rules, thereby generating new assertions.

• Backward chaining: begins with a proposed concluBackward chaining: begins with a proposed conclusion and tries to match it with the “then” clauses sion and tries to match it with the “then” clauses of rules. It then looks at the corresponding “if” clof rules. It then looks at the corresponding “if” clauses and tries to match those with assertions.auses and tries to match those with assertions.

Software Components of TCP/IP Software Components of TCP/IP

Application Layer Application Layer • Examples: SMTP (mail), Telnet, FTP, Rlogin, NFS, … Examples: SMTP (mail), Telnet, FTP, Rlogin, NFS, …

Transport Layer Transport Layer • The transport uses two protocols, UDP and TCP. UDP which stands fThe transport uses two protocols, UDP and TCP. UDP which stands f

or User Datagram Protocol does not guarantee packet delivery and aor User Datagram Protocol does not guarantee packet delivery and applications which use this must provide their own means of verifying pplications which use this must provide their own means of verifying delivery. TCP does guarantee delivery of packets to the applications delivery. TCP does guarantee delivery of packets to the applications which use it. which use it.

Network Layer Network Layer • The network layer is concerned with packet routing and used low levThe network layer is concerned with packet routing and used low lev

el protocols such as ICMP, IP, and IGMP. In addition, routing protocolel protocols such as ICMP, IP, and IGMP. In addition, routing protocols such as RIP, OSPF, and EGP will be discussed. s such as RIP, OSPF, and EGP will be discussed.

Link Layer Link Layer • The link layer is concerned with the actual transmittal of packets as The link layer is concerned with the actual transmittal of packets as

well as IP to Ethernet address translation. This layer is concerned witwell as IP to Ethernet address translation. This layer is concerned with Arp, the device driver, and Rarp. h Arp, the device driver, and Rarp.