Introduction to XML

About 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.

Reasons of using XML

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

1. 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.

2. 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.

3. Stylability

When display matters, the style sheet 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 style sheets 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

4. Universally Processed

Apart from being valid, restrictions are imposed on an 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.

5. Hierarchical Approach

XML documents get benefited 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.

6. Inline Reusability

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 onepiece document.