Keyword Search in Databases- P2 pot

It has become highly desirable to provide users with flexible ways to query/search information over databases as simple as keyword search like Google search.. This book surveys the recen

It has become highly desirable to provide users with flexible ways to query/search information over databases as simple as keyword search like Google search

This book surveys the recent developments on keyword search over databases, and focuses on finding structural information among objects in a database using a set of keywords Such structural information to be returned can be either trees or subgraphs representing how the objects, that contain the required keywords, are interconnected in a relational database or in an XML database The structural keyword search is completely different from finding documents that contain all the user-given keywords The former focuses on the interconnected object structures, whereas the latter focuses on the object content

The book is organized as follows In Chapter 1, we highlight the main research issues on the structural keyword search in different contexts In Chapter 2, we focus on supporting structural keyword search in a relational database management system using the SQL query language We concentrate on how to generate a set of SQL queries that can find all the structural information among records in a relational database completely, and how to evaluate the generated set of SQL queries efficiently In Chapter 3, we discuss graph algorithms for structural keyword search by treating

an entire relational database as a large data graph In Chapter 4, we discuss structural keyword search

in a large tree-structured XML database In Chapter 5, we highlight several interesting research issues regarding keyword search on databases

The book can be used as either an extended survey for people who are interested in the structural keyword search or a reference book for a postgraduate course on the related topics

KEYWORDS

keyword search, interconnected object structures, relational databases, XML databases,

data stream, rank

To my wife, Hannah

my children, Michael and Stephen

Jeffrey Xu Yu

To my wife, Michelle

my parents, Hanmin and Yaping

Lu Qin

To my parents, Qiyuan and Yumei

Lijun Chang

Contents

Preface xi

1 Introduction 1

2 Schema-Based Keyword Search on Relational Databases 3

2.1 Introduction 3

2.2 Candidate Network Generation 12

2.3 Candidate Network Evaluation 21

2.3.1 Getting All MTJNT s in a Relational Database 22 2.3.2 Getting Top-k MTJNT s in a Relational Database 29 2.4 Other Keyword Search Semantics 34

3 Graph-Based Keyword Search 45

3.1 Graph Model and Problem Definition 45

3.2 Polynomial Delay and Dijkstra’s Algorithm 49

3.3 Steiner Tree-Based Keyword Search 53

3.3.1 Backward Search 53 3.3.2 Dynamic Programming 55 3.3.3 EnumeratingQ-subtrees with Polynomial Delay 57 3.4 Distinct Root-Based Keyword Search 69

3.4.1 Bidirectional Search 69 3.4.2 Bi-Level Indexing 71 3.4.3 External Memory Data Graph 73 3.5 Subgraph-Based Keyword Search 76

x CONTENTS

4 Keyword Search in XML Databases 83

4.1 XML and Problem Definition 83

4.2 SLCA-Based Semantics 88

4.3 Identify Meaningful Return Information 98

4.4 ELCA-Based Semantics 106

4.5 Other Approaches 112

5 Other Topics for Keyword Search on Databases 115

5.1 Keyword Search Across Databases 115

5.2 Keyword Search on Spatial Databases 120

5.3 Variations of Keyword Search on Databases 123

Bibliography 133 Authors’ Biographies 143