Web Application Architecture: Principles, Protocols and Practices, 2nd Edition

Chapter 5. XML Languages and Applications

IN THIS CHAPTER

• Core XML

• XHTML

• Web services (SOAP and REST)

• Extensible Stylesheet Language (XSL)

OBJECTIVES

• Discuss core XML technologies setting the stage for the overview of XML applications and derivative technologies.

• Discuss XML DTDs, their limitations, and the advantages of XML Schemas.

• Consider XHTML as an XML application, discussing the differences and convergence between XHTML and HTML.

• Discuss XHTML Mobile Profile – a simplified version of XHTML for wireless applications.

• Provide insights about the advantages and drawbacks associated with competing web services strategies.

• Discuss XSL, showing how XSL Transformations and XSL Formatting Objects can be used to transform XML content and produce printable documents.

For all its power, SGML has remained a niche language. It originated in the 1970s and enjoyed a very strong following in the text representation community. However, the price for the power and flexibility of SGML was its complexity. Just as the simplicity of HTTP gave birth to the web, something a lot simpler than SGML was needed in the area of markup languages. The initial approach was to create a targeted SGML application, HTML, which worked relatively well during the early years of the web. However, it was neither sufficiently powerful and flexible, nor rigorous enough for the information-processing needs of sophisticated web applications.

The solution was to define a relatively simple subset of SGML that would retain the most critical ...