Essential XML

The Extensible Markup Language (XML) has been anointed as the universal duct tape for all software integration problems despite XML's relatively humble origins in the world of document management systems. Essential XML presents a software engineering-focused view of XML and investigates how XML can be used as a component integration technology much like COM or CORBA. Written for software developers and technical managers, this book demonstrates how XML can be used as the glue between independently developed software components (or in the marketecture terminology du jour, how XML can act as the backplane for B2B e-commerce applications).

Authors Don Box, Aaron Skonnard, and John Lam cover the key issues, technologies, and techniques involved in using XML as the adhesive between disparate software components and environments. They explain the fundamental abstractions and concepts that permeate all XML technologies, primarily those documented in the XML Information Set (Infoset). XML-based approaches to metadata, declarative, and procedural programming through transformation and programmatic interfaces are covered. Don Box, co-author of the Simple Object Access Protocol (SOAP) specification, provides readers with insight into this emerging XML messaging technology for bridging COM, CORBA, EJB, and the Web.

Readers acquire a better understanding of XML's inner workings and come to see how its platform, language, and vendor independence--along with its accessibility--make it an extraordinarily effective solution for software interoperation.

Table of Contents

Preface xiii

1 Beyond Markup 1

Document Basics 5
Names 9
Processing Instructions 13
Entities 15
Types and XML 23
Serialization Details 25
Where Are We? 29

2 Programming XML 31

Simple API for XML Version 2 (SAX2) 32
Auxiliary SAX Interfaces 44
SAX and I/O 50
SAX Error Handling 53
The Glue of SAX: XMLReader 56
The Document Object Model 61
The Object Model 63
The DOM and Factories 66
The Node Interface 70
Parents and Children 74
Nonhierarchical Nodes 82
Text Nodes 85
Element and Attribute Nodes 87
Document, Document Type, and Entity Nodes 90
Bulk Insertion Using Document Fragment 92
DOM Error Handling 93
Implementation vs Interface 94
DOM Traversal 97
Where Are We? 100

3 Navigation 101

XPath Basics 102
XPath Expressions 105
XPath Functions 123
XPath Abbreviations 133
Navigation and URIs 135
URI + XPath == XPointer 137
Ranges and Points 139
Where Are We? 140

4 XML Schemas 143

Schema Basics 144
Type Definitions 148
Element Declarations 153
Complex Types 156
Content Models and Particles 162
Attributes 172
Extensibility 174
Types Revisited 182
Reference and Uniqueness Constraints 190
Where Are We? 197

5 Transforms 199

XSLT Basics 203
Template-based Programming 217
Namespaces and XSLT 221
Generated Output 225
Multiple Stylesheets 231
Pattern-based Templates 234
Controlling Output 240
Where Are We? 244

6 Beyond Interface-based Programming 245

Where Are We? 245
Leaving Home 251
XML as a Better Component Model 254
Documents as Messages 262
Where Are We Going? 266

Appendix A: The XML Information Set (Infoset) 269

W3C Working Draft 20 December-1999 269
Abstract 270
Status of this Document 270
Contents 270
1. Introduction 271
2. Information Items 272
3. Example 286
4. Conformance 287
5. What is not in the Information Set 287
6. References 289
Appendix A: XML 1.0 Reporting Requirements (informative) 289
Appendix B: RDF Schema (informative) 291

Appendix B: XML Productions 299

Sorted by production number 299
Sorted by name 303
Character Tables 307

Appendix C: Example Gallery 311

SAX/DOM Examples 311
XPath Expressions 318
Programming XPath 320
XML Schema Examples 324
XSLT Examples 333
Programming XSLT 347

Index 353