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
There are number of reasons that contributes to the
XML's increasing acceptance , few of them are:
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.
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.
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
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.
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.
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
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!
File Converters - Many applications have
been written to convert existing documents into the XML standard. An example is
a PDF to XML converter.
VoiceXML - Converts XML documents into
an audio format so that a user can listen to an XML document.
and many more........