Chapter 13 Artificial Intelligence

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

A Division of Labor Three categories of tasks: Three categories of tasks: Computational tasks:Computational tasks: Adding numbers, sorting, searching Adding numbers, sorting, searching Calculating the trajectory for the space shuttle Calculating the trajectory for the space shuttle Recognition tasks:Recognition tasks: Recognizing your best friend Recognizing your best friend Understanding the spoken word Understanding the spoken word Reasoning tasks:Reasoning tasks: Planning what to wear today Planning what to wear today Deciding company ’ s strategic directions Deciding company ’ s strategic directions

Human and Computer Capabilities

Knowledge Representation Methods Natural language Natural language Formal language Formal language Pictorial Pictorial Graphical: e.g., semantic net Graphical: e.g., semantic net

Requirements Adequacy: the representation method must be adequate to capture all of the relevant knowledge. Adequacy: the representation method must be adequate to capture all of the relevant knowledge. Efficiency: we want the representation form to be minimalist. Efficiency: we want the representation form to be minimalist. Extendability Extendability Appropriateness Appropriateness

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

Artificial Neural Networks Simulate the connectionist architecture of human brain Simulate the connectionist architecture of human brain Applied to recognition task Applied to recognition task A neural network for comparing two characters A neural network for comparing two characters What happens when two As are presented? What happens when two As are presented? One A and one Y? One A and one Y? Perceptrons Perceptrons Back-propagation algorithm Back-propagation algorithm

Reasoning Tasks Intelligent searching Intelligent searching Decision tree for sequential searchDecision tree for sequential search Decision tree for binary searchDecision tree for binary search Best-first search Best-first search Means-end analysis Means-end analysis Search the Internet: spider Search the Internet: spider

Intelligent Agent A software technology designed to interact collaboratively with a user somewhat in the mode of a personal assistant. A software technology designed to interact collaboratively with a user somewhat in the mode of a personal assistant. Examples: Examples: Desktop office software  Office 小幫手Desktop office software  Office 小幫手 Personalized Web search enginePersonalized Web search engine Buying and selling agentsBuying and selling agents Electronic travel agentsElectronic travel agents

Expert Systems Rule-based systems Rule-based systems Knowledge-based systems Knowledge-based systems Contains two components: Contains two components: A knowledge base: a set of facts about the subject matterA knowledge base: a set of facts about the subject matter An inference engine: a mechanism for selecting the relevant facts and for reasoning from them in a logical wayAn inference engine: a mechanism for selecting the relevant facts and for reasoning from them in a logical way

The Reasoning Process Modus ponens: method of assertion Modus ponens: method of assertion Inference engines for rule-based system can proceed in: Inference engines for rule-based system can proceed in: Forwarding chaining: begins with assertions and tries to match those assertions to the “ if ” clauses of rules, thereby generating new assertions.Forwarding chaining: begins with assertions and tries to match those assertions to the “ if ” clauses of rules, thereby generating new assertions. Backward chaining: begins with a proposed conclusion and tries to match it with the “ then ” clauses of rules. It then looks at the corresponding “ if ” clauses and tries to match those with assertions.Backward chaining: begins with a proposed conclusion and tries to match it with the “ then ” clauses of rules. It then looks at the corresponding “ if ” clauses and tries to match those with assertions.

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 for User Datagram Protocol does not guarantee packet delivery and applications which use this must provide their own means of verifying delivery. TCP does guarantee delivery of packets to the applications which use it.The transport uses two protocols, UDP and TCP. UDP which stands for User Datagram Protocol does not guarantee packet delivery and applications which use this must provide their own means of verifying delivery. TCP does guarantee delivery of packets to the applications which use it. Network Layer Network Layer The network layer is concerned with packet routing and used low level protocols such as ICMP, IP, and IGMP. In addition, routing protocols such as RIP, OSPF, and EGP will be discussed.The network layer is concerned with packet routing and used low level protocols such as ICMP, IP, and IGMP. In addition, routing protocols 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 well as IP to Ethernet address translation. This layer is concerned with Arp, the device driver, and Rarp.The link layer is concerned with the actual transmittal of packets as well as IP to Ethernet address translation. This layer is concerned with Arp, the device driver, and Rarp.