<?xml version=”1.0” encoding=”UTF-8”?> <person> <first-name>Larry</first-name> <last-name>Kim</last-name> </person> 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 document’s content (first-name, last-name). As you  can  see  in  the  preceding  example,  the  document’s  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. XML Schemas An XML Schema is the World Wide Web Consortium’s (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 2 XMLSPY Handbook