<?xml version=1.0 encoding=UTF-8?>
As the preceding code snippet illustrates, XML is unique in comparison to other
information storage formats (for example, word processor, text, and spreadsheet
files) in that it contains both the content (Larry Kim) and additional markup
describing the semantics of the documents content (first-name, last-name). As
you can see in the preceding example, the documents content and markup are
interwoven within the code.
XML markup resembles HTML syntax to some extent; but unlike HTML, XML
has no pre-defined tag set (such as Title, H1, Head, and Body). Instead, XML pro-
vides a general facility and syntax for defining tags and the structural relationships
between them. The idea is that developers can then use this general form to create
customized XML-based tag sets (also known as markup languages or custom XML
vocabularies) for describing documents specific to their organization or industry.
XML can be used as a flexible way to create common information formats and
share content and information on the Internet.
There are many different kinds of XML documents currently used in the software
industry. In addition, new XML document standards are being developed by various
industry consortiums to address increasingly advanced functionality across virtu-
ally any vertical industry.
The vast majority of XML documents (or XML technologies) can be categorized
as either a core XML infrastructure technology or as providing an XML-based
vocabulary for a particular application or industry. This book focuses on core XML
infrastructure technologies: XML Schemas, XSL/XSLT, SOAP, and WSDL, which are
introduced in the following sections. Later chapters are entirely dedicated to
designing and editing documents in each technology.
The important concept to grasp is that XML Schemas, XSL/XSLT, and SOAP are
all simply XML documents. IT professionals, like you, must eventually design and
edit these types of documents. Having a solid understanding of the core XML infra-
structure technologies can give you a clear picture of what XML is and how the
various technologies work together to solve a wide variety of technical challenges.
An XML Schema is the World Wide Web Consortiums (W3C) official XML docu-
ment definition language. It addresses many shortcomings associated with
Document Type Definitions (DTD) and has industry support from all major software
corporations. An XML Schema is an XML document that defines the structure and