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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.
What you should already know
Before you continue you should have some basic understanding of
the following:
· WWW, HTML and the basics of building Web pages
· Web scripting languages like JavaScript or VBScript
What is XML?
· 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
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 anything. 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.
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.
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.
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