XML: An Introduction

What is XML?

"XML is a cross-platform, software and hardware independent tool for transmitting information"

XML is a W3C Recommendations. It stands for Extensible Markup Language . It  is a markup language much like HTML used to describe data. In XML, tags are not predefined. A user  defines his own tags and XML document structure like Document Type Definition (DTD) , XML Schema to describe the data. Hence it is self-descriptive too.There is Nothing Special About XML It is just plain text with the addition of some XML tags enclosed in angle brackets. In a simple text  editor, the XML document is easily visible .

Why Is XML So Important?

There are number of reasons that contributes to the  XML's  increasing acceptance , few of them are:

Plain Text

In XML it is easy to create and edit files with anything from a standard text editor to a visual development environment. XML also provides scalability for anything from small configuration files to a company-wide data repository.

Data Identification

The markup tags in XML documents identifiy the information and break up the data into parts for example.. a search program can look for messages sent to particular people from the rest of the message. Different parts of the information are  identified and further  they can be used in different ways by different applications.

Stylability

When display  matters, the stylesheet standard, XSL (an advance feature of  XML), lets you dictate over the convectional designs ( like using HTML)  to portray the data. XML being style-free, uses  different stylesheets  to produce output in postscript, TEX, PDF, or some new format that hasn't even been invented yet. A user can use a simple XML document  to display data in diverse  formats like

• a plain text file
• an XHTML file
• a WML (Wireless Markup Language) document suitable for display on a PDA
• an Adobe PDF document suitable for hard copy
• a VML (Voice Markup Language) dialog for a voicemail information system
• an SVG (Scalable Vector Graphic) document that draws pictures of thermometers and water containers

Universally Processed

Apart from being valid , restrictions are imposed on a xml file to abide by a DTD or a Schema  to make it well-formed .Otherwise, the XML parser won't be able to read the data. XML is a vendor-neutral standard, so a user can choose among several XML parsers to  process XML data.

Hierarchical Approach

XML documents get benefitted from their hierarchical structure. Hierarchical document structures are, faster to access. They are also easier to rearrange, because each piece is delimited. This makes xml files easy to  modify and maintain.

Inline Reusabiliy

XML documents  can be composed of separate entities. XML entities can be included "in line" in a XML document. And this included sections look like a normal part of the document .A user can single-source a section so that an edit to it is reflected everywhere the section is used, and yet a document composed  looks  like a one-piece document.

How Can You Use XML?

Few Applications of XML

Although there are countless  applications that use XML, here are a few examples of the  applications that are making use of this technology.

Refined search results - With XML-specific tags, search engines can give users more refined search results. A search engine seeks the term in the tags, rather than the entire document, giving the user more precise results.

EDI Transactions - XML has  made electronic data interchange (EDI) transactions accessible to a broader set of users. XML  allows data to be exchanged, regardless of the computing systems or accounting applications being used.

Cell Phones - XML data is sent to some cell phones, which is then formatted by the specification of the cell phone software designer to display text, images and even play sounds!

VoiceXML - Converts XML documents into an audio format so that a user can listen to an XML document.

and many more........