Concepts

One of the strengths of XML as a language for data exchange is its flexibility. An XML document can be transformed into many text formats, including HTML, PDF, and WML. This tutorial uses XML, XSL and JavaScript to create an interactive view of a purchase order. The combined code adds icons and user interface widgets that a user can click to expand or collapse branches of a tree-style view (also called outline view) of the data in an XML document.

About XML

XML stands for eXtensible Markup Language. Like HTML, XML is a subset of SGML (Structured Generalized Markup Language), optimized for delivery over the Web. Unlike HTML, which tags elements in Web pages for presentation by a browser, e.g. <bold>Oracle</bold>, XML tags elements as data, e.g. <company>Oracle</company>. For example, you can use XML to give context to words and values in Web pages, identifying them as data instead of simple textual or numeric elements.

About XSL

Unlike HTML, XML can keep the instructions for presenting data separate from the data itself. The XML tags define the structure and content, and then a stylesheet is applied to it to define the presentation. XML data can be presented in a variety of ways (both in appearance and organization) simply by applying different stylesheets to it. For example, a different interface can be presented to different users based on user profile, browser type, or other criteria by defining a different stylesheet for each different presentation style. Or, stylesheets can be used to transform XML data into a format tailored to the specific application or device that receives and processes the data. Stylesheets may be applied either on the server or on the client.

About JavaScript

Netscape's documentation describes JavaScript this way:

"JavaScript is Netscape's cross-platform, object-oriented scripting language. JavaScript is a small, lightweight language; it is not useful as a standalone language, but is designed for easy embedding in other products and applications, such as web browsers. Inside a host environment, JavaScript can be connected to the objects of its environment to provide programmatic control over them."