Introduction

[Introduction][Goals of XML][XML vs HTML][How to write XML]

What you should already know

Before you continue you should have some basic understanding of the following:

WW, HTML and the basics of building Web pages

Web scripting languages like JavaScript or VBScript

What is XML?

Extensible Markup language is currently the most promising language for storing an d delivering information on the WWW. XML has a highly flexible syntax that a;;ows you to use it and describe almost any kind of information (hence the term Extensible). Because an XML document so effectively structures and labels the information it contains, the browser can find, sort, arrange and manipulate that information in very flexible ways.

XML was defined by tge XML working group of the World Wide Web Consortium (W3C)

XML stands for EXtensible Markup Language

XML is a markup language much like HTML.

XML was designed to describe data.

XML tags are not predefined in XML. You must define your own tags.

XML uses a DTD (Document Type Definition) to describe the data.

XML with a DTD is designed to be self describing.

The main difference between XML and HTML

Although the set of predefined HTML elements has expanded considerably since the first HTML version, HTML is still unsuitable for defining many types of documents. The following are some examples

A document that doesn’t consitst of typical components (headings, paragraphs etc). HTML lacks the elements necessary to mark a musical score or a set of mathematical equations.

A database, such as an inventory of books You can use HTML only for statical information. You can’t use HTML to store, find and sort onformation.

A document that you want to organize in a tree like structure. A program could use this strucure to create a table of contents.

XML was designed to carry data.

XML is not a replacement for HTML.

XML and HTML were designed with different goals:

XML was designed to describe data and to focus on what data is.

HTML was designed to display data and to focus on how data looks.

HTML is about displaying information, XML is about describing information.

XML does not DO anything

XML was not designed to DO anything.

Maybe it is a little hard to understand, but XML does not DO anything. XML was not made to DO something. XML is created as a way to structure, store and send information.

The following example is a note to Tove from Jani, stored as XML:

<note>
<to>Tove</to>
<from>Jani</from>
<heading>Reminder</heading>
<body>Don't forget me this weekend!</body>
</note>

The note has a header, and a message body. It also has sender and receiver information. But still, this XML document does not DO anything. It is just pure information wrapped in XML tags. Someone must write a piece of software to send it, receive it or display it.

You can create your own elements and assign tem any names you like. So you can use XML to define any type of document.

For example if you want to describe a list of books
<?xml version="1.0"?>

<INVENTORY>
<BOOK>
<TITLE>The Adventures of Huckleberry Finn</TITLE>
<AUTHOR>Mark Twain</AUTHOR>
<BINDING>mass market paperback</BINDING>
<PAGES>298</PAGES>
<PRICE>$5.49</PRICE>
</BOOK>
<BOOK>
<TITLE>The Adventures of cedefop</TITLE>
<AUTHOR>Stella Papargeris</AUTHOR>
<BINDING>mass market paperback</BINDING>
<PAGES>100</PAGES>
<PRICE>$15.49</PRICE>
</BOOK>
</INVENTORY>

XML is free and extensible

XML tags are not predefined. You must "invent" your own tags.

The tags used to markup HTML documents and the structure of HTML documents are predefined. The author of HTML documents can only use tags that are defined in the HTML standard (like <p> and <h1>.....).

XML allows the author to define his own tags and his own document structure

The tags in the example above (like <to> and <from>), are not defined in any XML standard. These tags are "invented" by the author of the XML document.

When used to describe a database, XML has a couple of advantages over other databases such as access. It is human readable.

XML document is structured in a treelike hierarchy, with elements completely nested within other lements and with a single top element.

XML is a complement to HTML

XML is not a replacement for HTML.

It is important to understand that XML is not a replacement for HTML. In future Web development it is most likely that XML will be used to describe the data, while HTML will be used to format and display the same data.

My best description of XML is as a cross-platform, software and hardware independent tool for transmitting information.

XML in future Web development

XML is going to be everywhere.

We have been participating in XML development since its creation. It has been amazing to see how quickly the XML standard has been developed, and how quickly a large number of software vendors have adopted the standard.

We strongly believe that XML will be as important to the future of the Web, as HTML has been to the foundation of the Web, and that XML will be the most common tool for all data manipulation and data transmission.