Chapter 11 Artificial Intelligence Introduction to CS 1 st Semester, 2015 Sanghyun Park

Outline  Introduction  Understanding Images  Reasoning  Artificial Neural Networks  Genetic Algorithms  Other Areas of Research

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

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

Eight-Puzzle Machine The design of eight-puzzle machine provides a basis for presenting the topics of the following two sections

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

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

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

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

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

State Graph: Example

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;

Sample Search Tree (1/2)

Sample Search Tree (2/2)

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

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 __

Algorithm for Control System Using Heuristics

Example: Beginning of Heuristic Search

Example: Search Tree After Two Passes

Example: Search Tree After Three Passes

Example: Complete Search Tree

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

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 _________

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

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

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

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

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

Process in Genetic Algorithms (2/2)

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

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”

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

A Semantic Net

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

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

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