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Chapter 11 Artificial Intelligence Introduction to CS 1 st Semester, 2015 Sanghyun Park
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Outline Introduction Understanding Images Reasoning Artificial Neural Networks Genetic Algorithms Other Areas of Research
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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
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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
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Eight-Puzzle Machine The design of eight-puzzle machine provides a basis for presenting the topics of the following two sections
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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 position by ____-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
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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
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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
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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
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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
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State Graph: Example
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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;
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Sample Search Tree (1/2)
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Sample Search Tree (2/2)
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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
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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 __
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Algorithm for Control System Using Heuristics
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Example: Beginning of Heuristic Search
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Example: Search Tree After Two Passes
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Example: Search Tree After Three Passes
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Example: Complete Search Tree
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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
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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 _________
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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
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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
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Example Networks 1 if two inputs differ, 0 otherwise 1 if both inputs are 1, 0 otherwise
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Genetic Algorithms Genetic algorithm applies our understanding of natural _______ to the problem-solving task This approach is to intermix the ____ performers within a 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
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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
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Process in Genetic Algorithms (2/2)
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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
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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”
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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 form that 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
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A Semantic Net
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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
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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
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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
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