Sams Teach Yourself XML in 21 Days

By Steven Holzner

• Table of Contents
  • About the Author
  • Acknowledgments
  • We Want to Hear from You!
  • Introduction
  • Part I: At a Glance
  • Day 1. Welcome to XML
  • Day 2. Creating XML Documents
  • Day 3. Creating Well-Formed XML Documents
    • What Makes an XML Document Well-Formed?
    • Creating an Example XML Document
    • Understanding the Well-Formedness Constraints
    • Using XML Namespaces
    • Understanding XML Infosets
    • Understanding Canonical XML
    • Summary
    • Q&A
    • Workshop
  • Day 4. Creating Valid XML Documents: DTDs
  • Declaring Attributes in DTDs
  • Day 6. Creating Valid XML Documents: XML Schemas
  • Day 7. Creating Types in XML Schemas
  • Part I. In Review
  • Day 8. Formatting XML by Using Cascading Style Sheets
  • Day 9. Formatting XML by Using XSLT
  • Day 10. Working with XSL Formatting Objects
  • Part II. In Review
  • Part III: At a Glance
  • Day 11. Extending HTML with XHTML
  • Day 12. Putting XHTML to Work
  • Day 13. Creating Graphics and Multimedia: SVG and SMIL
  • Day 14. Handling XLinks, XPointers, and XForms
  • Part III. In Review
  • Part IV: At a Glance
  • Day 15. Using JavaScript and XML
  • Day 16. Using Java and .NET: DOM
  • Day 17. Using Java and .NET: SAX
  • Day 18. Working with SOAP and RDF
  • Part IV. In Review
  • Part V: At a Glance
  • Day 19. Handling XML Data Binding
  • Day 20. Working with XML and Databases
  • Day 21. Handling XML in .NET
  • Part V. In Review
  • Appendix A. Quiz Answers

Summary

Today, you took a look at how to create well-formed XML documents. W3C doesn't even consider an XML document to be XML unless it's well-formed. W3C considers an XML document well-formed if it meets three criteria:

• Taken as a whole, it matches the production labeled document.
• It meets all the well-formedness constraints given in this specification (that is, the XML 1.0 specification, http://www.w3.org/TR/REC-xml).
• Each of the parsed entities, which is referenced directly or indirectly within the document, is well-formed.

The most general of these items says that an XML document must meet the well-formedness constraints in the XML specification, and you took a look today at what that meant.

Those constraints include beginning a document with an XML declaration, using only legal character references, the document must include at least one element, elements must be structured and nested correctly, the root element must contain all other elements, attribute names must be unique, attribute values must be quoted, and so on.

You also took a look at creating namespaces, and how namespaces help you avoid conflicts in XML. To define a namespace, you can assign the xmlns: prefix attribute to a unique identifier (usually a URI), or you can use the xmlns attribute to define a default namespace.

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