Oracle JDeveloper You can use any development tool you wish to develop XSQL pages, but Oracle JDe- veloper offers some advantages. It is a development environment for building all types of Java and Java 2 Enterprise Edition (J2EE) applications with great support for XML. It highlights your text for you, provides easy lookup of Java classes, and checks the syntax of your XML and XSLT documents. In addition, you get the project manage- ment capabilities found in most development environments. Because XSQL pages are also XML documents, the XML syntax checking will keep your  documents  well  formed.  JDeveloper  also  provides  specific  support  for  XSQL page  development.  It  will  perform  XSQL-specific  syntax  checking  and  will  interac- tively execute your code. When you get into the development of action handlers and serializers later in the book, you can use it to interactively debug your Java code. The approach of this book is to be a development tool agnostic. All of the various types of files—Java, XSLT, and XSQL—are all text files that can be developed with any text editor. This said, JDeveloper is tuned for XSQL page development. If you haven’t already found a development environment that you like, JDeveloper is an obvious and promising candidate. Introduction to XML Now that you have an overview of the XSQL architecture, it is time to explore the nitty- gritty of XSQL. As with any language, you also need to know a bit about the syntax. Because all XSQL documents are also XML documents, the syntax is actually defined by XML. XSLT is also an XML-based language, so the same is true for it. This means that you need to learn a bit of the basics of XML. XML is a very simple language. Its power lies partly in this simplicity. With XML, you  have  an  easy,  industry-standard  way  to  package  data.  Because  XML  parsers are  prevalent,  anyone  can  parse  your  XML  document  and  get  at  your  data.  Most important, you can design exactly how you want your data structured. Here, you are going to learn the basics of XML. Our aim is to educate you on the structure of XML documents. The Role of XML XML is a metalanguage that allows you to define your own markup languages. It is a project of the World Wide Web Consortium (W3C) and is an open standard. An XML document looks a lot like an HTML page, but they serve different purposes. Whereas HTML tells a Web browser how to present data, XML is about structuring data. XML  is  best  understood  as  a  child  of  Standard  Generalized  Markup  Language (SGML). SGML is also the parent of HTML, so XML and HTML can be considered cousins, and SGML can be considered the mother tongue. SGML has been in use since the mid-1980s as a way to describe and organize complex documents. Among other Introducing Oracle XSQL 13 271209 Ch01.F  12/9/02  2:00 PM  Page 13