Chapter 11 Artificial Intelligence

1. Chapter 11Artificial Intelligence Introduction to CS 1st Semester, 2012 Sanghyun Park

2. Outline • Introduction • Understanding Images • Reasoning • Artificial Neural Networks • Genetic Algorithms • Other Areas of Research

3. Definition • ________________ (AI) is a branch of science which deals with helping machines find solutions to complex problems in a more _________ fashion • This generally involves borrowing characteristics from human _________, and applying them as _________ in a computer friendly way • AI is generally associated with ________ science, but it has many important links with other fields such as math, psychology, cognition, and biology

4. Motivation • Computers are fundamentally well suited to perform __________ tasks efficiently and reliably • Unlike humans, computers have trouble understanding ______ situations, and _______ to new situations • AI aims to improve machine behavior in tackling such complex tasks • Much of AI research aims to understand our intelligent behavior. Humans have an interesting approach to problem-solving, based on _______ thought, high-level deliberative _________ and pattern recognition

5. Eight-Puzzle Machine The design of eight-puzzle machine provides a basisfor presenting the topics of the following two sections

6. Understanding Images (1/2) • The first intelligent behavior is to understand the _____ in order to extract the status of the puzzle • Our machine can detect which tile is in which positionby ____-by-____ comparisons • But it requires a certain degree of ________ among the style, size and orientation of the symbols being read • Another approach is based on the matching of the ________ characteristics • This method involves two steps • Extract the features from the image being processed • Compare the features to those of known symbols

7. Understanding Images (2/2) • The task of understanding general images is usually approached as a two-step process: image processing and image analysis • Image processing refers to ________ characteristics of the image • Edge enhancement • Region finding • Smoothing • Image analysis refers to the process of ____________ what these characteristics mean

8. Reasoning • Once our puzzle-solving machine has deciphered the _______ of the tiles, its task becomes that of figuring out what ______ are required to solve the puzzle • An approach to this problem is to __________ the machine with solutions to all possible arrangements of the tiles • However this approach is not possible when time and storage _________ are considered • Therefore the machine must be programmed to perform elementary _________ activities

9. Production Systems • A large class of reasoning problems have common characteristics; these common characteristics are isolated in a system known as a _________ system • A production system consists of three main components • A collection of _____: each state is a situation that might occur in the application environment • A collection of _________: a production is an operation to shift the system from one state to another • A _____ system: it consists of the logic that solves the problem of moving the system from the _____ state to the goal state

10. State Graph • An important concept in the development of a control system is that of a _____ graph • A state graph consists of a collection of nodes representing the _____ in the system connected by arrows representing the __________ that shift the system from one state to another • When viewed in terms of the state graph, the problem faced by the control system becomes that of finding a sequence of _____ that leads from the start state to the ____ state

11. State Graph: Example

12. Search Trees • We have seen that the control system’s job involves searching the state graph to find a ____ from the start node to the goal • One strategy is to construct a ______ tree that consists of the part of the state graph that has been __________ by the control system • Let us consider the following start state;

13. Sample Search Tree (1/2)

14. Sample Search Tree (2/2)

15. Heuristics (1/2) • The search tree can become quite _____ if the goal is not quickly reached • One strategy is to change the order in which the search tree is constructed; rather than building it as a _______-first manner, we can pursue the more promising paths to greater depths --- _____-first construction • We need a way of identifying which of several states appears to be the most ________ • Our approach is to use a _______, which is a quantitative value associated with each state that estimates the _______ from that state to the goal

16. Heuristics (2/2) • A simple heuristic in the case of the eight-puzzle would be to estimate the distance to the goal by _______ the number of tiles that are out of place • However this heuristic does not take into account how ___ out of position the tiles are • A better heuristic is to measure the distance each tile is from its destination and add these values to obtain a single quantity Heuristic value is__

17. Algorithm for Control SystemUsing Heuristics

18. Example:Beginning of Heuristic Search

19. Example:Search Tree After Two Passes

20. Example:Search Tree After Three Passes

21. Example:Complete Search Tree

22. Artificial Neural Networks • CPUs that execute sequences of instructions do not seem capable of perceiving and reasoning like _______ • Many researchers are turning to machines with other architectures; one of these is the artificial neural network • Artificial neural networks are constructed from many processing units, in a manner that models networks of _______ in living biological systems

23. A Neuron in a Living Biological System • The signals transmitted via a cell’s ____ reflect whether the cell is in an ________ or excited state • This state is determined by the combination of signals received by the cell’s _________

24. Activities Within a Processing Unit • A processing unit is a simple device that mimics this basic understanding of the biological _______ • It produces an output of 1 or 0, depending on whether its ________ input exceeds a given ________ value • This effective input is a weighted sum of the actual inputs

25. Weights Within a Processing Unit • Representation of a processing unit • The fact that a weight can be positive or negative means that the corresponding input can have either an inhibiting or _______ effect on the receiving unit • Actual size of the weight controls the _______ of effect • By _________ the values of the weights throughout an artificial neural network, we can program the network to respond to different inputs in a predetermined manner

26. Example Networks 1 if two inputs differ,0 otherwise 1 if both inputs are 1,0 otherwise

27. Genetic Algorithms • Genetic algorithm applies our understanding of natural _______ to the problem-solving task • This approach is to intermix the ____ performers withina collection of proposed solutions to obtain another generation of better proposed solutions • By repeating this process, one hopes to simulate the __________ process and ultimately obtain solution

28. Process in Genetic Algorithms (1/2) • One finds a way to represent potential solutions as ______ of symbols • A collection of potential solutions is generated and tested • The better solutions from this collection are then ______ to form a new generation of potential solutions • At times random __________ may be inserted during the crossing process

29. Process in Genetic Algorithms (2/2)

30. Evolutionary Programming • The goal is to develop programs by allowing them to _______ rather than by explicitly writing them • An important step in this setting is to find ways in which parts of programs can be ____________ to produce meaningful new programs • The ________ programming paradigm has proved useful in this context • A major problem is to identify the “best performers” out of a group of programs of which none seem to be anywhere close to the desired product

31. Natural Language Processing (NLP) • A statement in a natural language can have ________ meanings depending on its context • To unravel the meaning of a statement in a natural language therefore requires several levels of analysis • The first level is ________ analysis that performs parsing to identify the grammatical role of each word • The next level is _________ analysis that identifies the semantic role of each word in the statement“Mary gave John a card” = “John got a card from Mary” • A third level is _________ analysis where the context of the sentence is brought into the understanding process“The bat flew from his hand”

32. Information Retrieval And Extraction • Another area of research in NLP concerns an ______ document rather than individual sentences • Information retrieval refers to the task of identifying documents that ______ to the topic at hand • Information extraction refers to the task of extracting information from documents so that it takes a formthat is useful in other applications • One such form is known as a _______ that is essentially a questionnaire in which specifics are recorded • Another form in which information extractors record information is known as _________ net

33. A Semantic Net

34. Robotics • The goal of the early research in robotics was to develop economically viable ________ line robots that could increase both productivity and consistency • Today, a major goal of research in robotics is to build __________ robots that can maintain their balance, walk up stairs, and navigate through rough terrain • Many creative techniques are being applied.One is the application of ___________ theories to robot development, which generated the field of evolutionary robotics

35. Database Systems • AI techniques are applied to traditional DB systems to provide better services. DB techniques are applied in AI projects to handle ________ amounts of knowledge • One topic is to identify and retrieve information that is ______ to a topic rather than merely the information that is explicitly requested • Another topic is the development of data storage and retrieval system that can provide information that is _______ by the stored data rather than merely respond with information that is explicitly stored

36. Expert Systems • Expert systems are software packages designed to assist humans in situations where an expert in a specific area is required • These systems simulate the cause-and-effect reasoning that experts would accomplish if confronted with the same situations • A major task in constructing an expert system is to obtain the required __________ from an expert • A next task is to _______ the knowledge into a format compatible with a software system • Knowledge base vs. inference engine