Tài liệu Querying XML, : XQuery, XPath, and SQL/XML in context pptx

Querying XML

XQuery, XPath, and SQUXML

in Context

The Morgan Kaufmann Series in Data Management Systems

Series Editor: Jim Gray, Microsoft Research

Querying XML: XQuery, XPath, and SQL/XML in

Context

Jim Melton and Stephen Buxton

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Database Modeling with Micros~" Visio for Enterprise

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Designing Data-Intensive Web Applications

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Mining the Web: Discovering Knowledge from

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Advanced SQL: 1999--Understanding Object￾Relational and Other Advanced Features

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Querying XML

XQuery, XPath, and SQL/XML

in Context

Jim Melton

and

Stephen Buxton

ELSEVIER

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Printed in the United States of America

06 07 08 09 10 5 4 3 2 1

To rescued Shelties, and Shelties in need of rescue, everywhere. Especially

to senior Shelties who, after years of devotion to their owners, are cruelly

discarded for the most pathetic of reasons: "We're thinking about

moving", "She's just in the way", "He's too old to be fun any more", and

the worst of all - "We're getting a puppy and, you know...". And to the

loving people who welcome these old dogs into their lives, knowing that

older Shelties are calmer, settled, cuddly, and devoted - they selflessly

deal with medical needs, arthritic limitations, and the piddles of old age.

Wonderful karma accrues to these people for giving these seniors love

and respect, allowing them to live out their lives in comfort and

happiness.

Jim

To my Mum and Dad, for their long, long journey.

Stephen

This Page Intentionally Left Blank

Contents

Foreword

Preface

Why the subject matter is important xix

Why we wrote this book xx

Who should read this book xxi

How the book is organized xxi

The example we're using xxiii

Syntax Conventions xxiii

9 Additional resources xxv

9 Type conventions xxv

9 Acknowledgements xxv

Part I XML: Documents and Data

Chapter I XML

I. I Introduction 3

1.2 Adding Markup to Data 3

1.2. I Raw Data 4

1.2.2 Separating Fields 4

1.2.3 Grouping Fields Together 5

1.2.4 Naming Fields 6

1.2.5 A Structural Map of the Data 8

1.2.6 Markup and Meaning 12

1.2.7 Why XML? 13

1.3 XML-Based Markup Languages 14

1.4 XML Data 19

1.4.1 Structured Data 19

1.4.2 Unstructured Data 20

xvii

xix

vii

viii Contents

1.5

1.6

1.4.3 Messages 20

1.4.4 XML Data ~ Summary 20

Some Other Ways to Represent Data 21

1.5. I SQL ~ Structure Only 21

1.5.2 Presentation Languages ~ Presentation Only 24

1.5.3 SGML 26

1.5.4 HTML 27

Chapter Summary 28

Chapter 2 Querying

2.1

2.2

2.3

2.4

Introduction 31

2. I. I Definitions of Query 3 I

Querying Traditional Data 32

2.2. I The Relational Model and SQL 33

2.2.2 Extensions to SQL 36

2.2.3 Querying Traditional Data ~ Summary 38

Querying Nontraditional Data 39

2.3. I Metadata 40

2.3.2 Objects 41

2.3.3 Markup 41

2.3.4 Querying Content 43

Chapter Summary 43

Chapter 3 Querying XML

3. I Introduction 45

3.2 Navigating an XML Document 46

3.2. I Walking the XML Tree 48

3.2.2 Some Additional Wrinkles 56

3.2.3 Summary ~Things to Consider 60

3.3 What DoYou Know about Your Data? 61

3.4 SomeWays to Query XMLToday 63

3.5 Chapter Summary 64

Part II Metadata and XML

Chapter 4 Metadata-- An Overview

4.1

4.2

4.3

4.4

Introduction 67

Structural Metadata 69

Semantic Metadata 75

Catalog Metadata 78

31

45

65

67

Contents ix

Chapter 5

Chapter 6

4.5

4.6

Integration Metadata 82

Chapter Summary 84

Structural Metadata

5.1

5.2

5.3

5.4

5.5

5.6

85

Introduction 85

DTDs 86

5.2.1 SGML Heritage 87

5.2.2 Relatively Simple, Easy to Write, and Easy to Read 88

5.2.3 Limited Capabilities, Especially with Respect to Data Types 94

5.2.4 An Example Document and DTD 97

XML Schema 100

5.3. I Exploring an XML Schema 101

5.3.2 Simple Types (Primitive Types and Derived Types) 107

5.3.3 Complex Types and Structures 110

Other Schema Languages for XML II 5

5.4.1 RELAX NG 115

5.4.2 Schematron 117

5.4.3 Decisions, Decisions, Decisions 118

Deriving an Implied Schema from a DTD II 9

Chapter Summary 120

The XML Information Set (Infoset)

and Beyond

6.1

6.2

6.3

6.4

6.5

6.6

6.7

6.8

6.9

123

Introduction 123

What Is the Infoset? 124

The Infoset Information Items and Their Properties 125

The Infoset vs.the Document 133

The XPath 1.0 Data Model 136

The Post-Schema-Validation Infoset (PSVI) 138

6.6. I Infoset + Additional Properties and Information Items 139

6.6.2 Additional Information in the PSVI 140

6.6.3 Limitations of the PSVI 141

6.6.4 Visualizing the PSVI 142

The Document Object Model (DOM)~An API 142

Introducing the XQuery Data Model 146

A Note Regarding Data Model Terminology 147

6.10 Chapter Summary and Further Reading 149

x Contents

Part III Managing and Storing XML for Querying 151

Chapter 7 Managing XML: Transforming and Connecting 153

7.1

7.2

7.3

7.4

7.5

Introduction 153

Transforming, Formatting, and Displaying XML 154

7.2. I Extensible Stylesheet Language Transformations (XSLT) 155

7.2.2 Extensible Stylesheet Language: Formatting

Objects (XSL FO) 162

The Relationships between XML Documents 163

7.3.1 XML Inclusions (Xlnclude) 164

7.3.2 XML Pointer Language (XPointer) 168

7.3.3 XML Linking Language (XLink) 173

Relationship Constraints: Enforcing Consistency 185

Chapter Summary 191

Chapter 8 Storing: XML and Databases

8. I Introduction 193

8.2 The Need for Persistence 194

8.2. I Databases 195

8.2.2 Other Persistent Media 200

8.2.3 ShreddingYour Data 20 I

8.3 SQL/XML's XMLType 206

8.4 Accessing Persistent XML Data 207

8.5 XML on the Fly: Nonpersistent XML Data 209

8.6 Chapter Summary 21 I

193

Part IV Querying XML 213

Chapter 9 XPath 1.0 and XPath 2.0

9.1

9.2

9.3

9.2.1

9.2.2

9.2.3

9.2.4

9.2.5

9.2.6

9.2.7

9.2.8

Introduction 215

XPath 1.0 217

Expressions 218

Contexts 222

Paths and Steps 224

Axes and Shorthand Notations 228

Node Tests 239

Predicates 241

XPath Functions 243

Putting the Pieces Together 248

XPath 2.0 Components 252

215

Contents xi

9.4

9.5

9.3.1 Expressions 252

9.3.2 The for and return Expressions 256

XPath 2.0 and XQuery 1.0 258

Chapter Summary 259

Chapter I0 Introduction to XQuery 1.0

10.1 Introduction 261

10.2 A Brief History 262

10.3 Requirements 264

10.3.1 General Requirements for XQuery 266

10.3.2 Data Model Requirements 267

10.3.3 XQuery Functionality Requirements 268

10.3.4 XPath 2.0 Requirements 269

10.4 Use Cases 269

10.5 The XQuery 1.0 Suite of Specifications 275

10.5.1 XQuery 1.0 Language Specification 276

10.5.2 XPath 2.0 and XQuery 1.0 Formal Semantics 278

10.5.3 XPath 2.0 and XQuery 1.0 Functions & Operators 278

10.5.4 XQuery 1.0 Serialization 279

10.5.5 XQueryX 280

10.6 The Data Model 280

10.6.1 Data Model Instances 282

10.6.2 What Is an XQuery Data Model Instance? 283

10.6.3 The Seven Kinds of Nodes 284

10.6.4 The Data Model as Tree- Representing aWelI-Formed

Document 293

10.6.5 The Data Model as Sequence- Representing an

Arbitrary Sequence 295

10.7 The XQueryType System 297

10.7. I What Is a Type System Anyway? 297

10.7.2 XML SchemaTypes 300

10.7.3 From XML Schema to the XQueryType System 304

10.7.4 Types and Queries 305

10.8 XQuery 1.0 Formal Semantics and Static Typing 306

10.8.1 Notations 307

10.8.2 Static Typing 31 I

10.8.3 Dynamic Semantics 312

10.9 Functions and Operators 313

10.9.1 Functions 313

10.9.2 Operators 316

10.10 XQuery 1.0 and XSLT 2.0 Serialization 319

261

xii Contents

10.10.1 XML Output Method 322

10.10.2 XHTML Output Method 325

10.10.3 HTML Output Method 326

10.10.4 Text Output Method 327

10.1 I Chapter Summary 327

Chapter II XQuery 1.0 Definition

I I.I Introduction 329

11.2 Overview of XQuery 330

11.2.1 Concepts 330

11.3 The XQuery Processing Model 333

11.3.1 The Static Context 334

11.3.2 The Dynamic Context 337

11.4 The XQuery Grammar 338

11.5 XQuery Expressions 339

I 1.5.1 Literal Expressions 341

11.5.2 Constructor Functions 342

11.5.3 Sequence Constructors 343

11.5.4 Variable References 345

11.5.5 Parenthesized Expressions 346

11.5.6 Context Item Expression 346

11.5.7 Function Calls 346

11.5.8 Filter Expressions 349

11.5.9 Node Sequence-Combining Expressions 349

I 1.5.10 Arithmetic Expressions 35 I

11.5. II Boolean Expressions: Comparisons and Logical

Operators 354

I 1.5.12 Constructors ~ Direct and Computed 361

11.5.13 Ordered and Unordered Expressions 370

I 1.5.14 Conditional Expression 371

I 1.5.15 Quantified Expressions 372

I 1.5.16 Expressions on XQueryTypes 374

I 1.5.17 Validation Expression 378

11.6 FLWOR Expressions 380

11.6.1 The for Clause and the let Clause 380

11.6.2 The where Clause 389

11.6.3 The order by Clause 390

11.6.4 The return Clause 392

11.7 Error Handling 393

11.8 Modules and Query Prologs 394

11.8.1 Prologs 395

329

Contents xiii

11.8.2 Main Modules 398

11.8.3 Library Modules 400

11.9 A Longer Example with Data 402

II. 10 XQuery for SQL Programmers 402

I1.11 Chapter Summary 403

Chapter 12 XQueryX

12.1 Introduction 407

12.2 How Far to Go? 408

12.2.1 Trivial Embedding 409

12.2.2 Fully-Parsed XQuery 410

12.2.3 The XQueryXApproach 41 I

12.3 The XQueryX Specification 416

12.4 XQueryX By Example 417

12.4.1 The Simplest XQueryX Example ~ 42 417

12.4.2 Simple XQueryX Example 423

12.4.3 Useful XQuery Example 430

12.5 Querying XQueryX 433

12.5. I Querying XQueryX for XQueryTuning 434

12.5.2 Querying XQueryX for Application Improvement 436

12.6 Chapter Summary 437

Chapter 13 What's Missing?

13.1

13.2

13.3

Introduction 439

Full-Text 440

13.2. I What Is a Full-Text Query? 440

13.2.2 Full-Text and XML 448

13.2.3 Defining XQuery Full-Text 449

13.2.4 W3C XQuery Full-Text ~ Grammar Extension 455

13.2.5 W3C XQuery Full-Text ~ Some Discussion Topics 471

13.2.6 XQuery Full-Text ~ Some Implementations 474

Update 478

13.3. I Motivation:Where/WhyWe Need Update 479

13.3.2 Requirements 481

13.3.3 Alternatives: Syntax and Semantics 485

13.3.4 How Products Handle Update Today 488

13.3.5 What Lies Ahead? 495

13.4 Chapter Summary 495

407

439

xiv Contents

Chapter 14 XQuery APIs

14.1 Introduction 497

14.2 Alphabet-Soup Review 498

14.2.1 ODBC andJDBC 499

14.2.2 DOM, SAX, StAX, JAXP, JAXB 501

14.2.3 Alphabet-Soup Summary 502

14.3 XQJ ~ XQuery for Java 503

14.3.1 Connecting to a Data Source 504

14.3.2 Executing a Query 507

14.3.3 Manipulating XML Data 509

14.3.4 Static and Dynamic Context 517

14.3.5 Metadata 518

14.3.6 Summary 519

14.4 SQL/XML 520

14.5 Looking Ahead 521

Chapter 1 5 SQIL/XML

15.1 Introduction 523

15.2 SQL/XML Publishing Functions 526

15.2.1 Examples 526

15.2.2 XMLAGG 529

15.2.3 XMLFOREST 531

15.2.4 XMLCONCAT 535

15.2.5 Summary 536

15.3 XML DataType 537

15.4 XQuery Functions 540

15.4.1 XMLQUERY 541

15.4.2 XMLTABLE 546

15.4.3 XMLEXISTS 570

15.5 Managing XML in the Database 572

15.6 Talking the Same Language ~ Mappings 573

15.6.1 Character Sets 573

15.6.2 Names 574

15.6.3 Types andValues 575

15.7 Chapter Summary 580

Part V Querying and The World Wide Web

Chapter 16 XML-Derived Markup Languages

16.1 Introduction 585

16.2 Markup Languages 586

497

523

583

585