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XML or Extensible Markup Language
is widely used for formatting data universally so that it can be exchanged over
the internet or to be published online. It is a markup language used for those
documents which contains structured information. When we talk of structured
information we mean contents like words or pictures and the role theses
contents play in a whole document. We often notice that content in the
beginning may mean introduction to the subject. The content in the end could be
the conclusion. The content for a picture could be a caption. These structures
make up a document. The markup language is the equipment which will recognize the
structure in a document. The XML specifications put forward a standard way by
which markup could be added to the documents.
XML was created so that it
becomes easy to use richly structured documents on the internet. The
alternative to XML is HTML and SGML which are not very effective as far are
structured document is concerned. A set of semantics bind HTML and arbitrary
structures are not provided by it. While SGML does provide arbitrary structure
but web browsers find it too difficult to handle. SGML can carry out vast
complicated problems but simple identification of structure requires too much
effort which can be avoided by using XML.
While discussing the role of XML
in data exchange format it is important to mention that XML is not a
replacement for either SGML or HTML. XML is a subset of SGML. HTML was
precisely designed to show how a data looks while it is displayed visually. It
is actually displays information. XML, on the other hand, was developed to
store data as well as transport it with stress on the type of the data. Instead
of displaying information XML carries information.
Function of XML is not to do
anything but simply transport information along with structuring and storing
it. It uses tags which are created by the writer of the XML document and is not
pre-defined like HTML. Given below is an example of XML structured content
where a message is sent from A to B:
<message>
<to>B</to>
<from>A</from>
<body>Kindly go through the
document</body>
</message>
This example makes it clear about
the structure of the message. XML employs to use such simple structure for all
its documents which makes it easy for its reader to decipher the text. That is
why it is such a popular tool for data exchange. With XML you have to invent
your own tags. The tags like <to> or <from> are not any standard
tag and have been put there by the writer of the message.
Any user can put his/her tag
specific to the document that is being created such as “address”, “educational
qualification”, “experience” while preparing Resume type of document which then
can be exchanged as a XML document. There are some XML tags that are applied to
all documents and there are other tags which are required to file definitions
in documents.
When it comes to data exchange
format, XML is especially useful in many professional fields, such as
meteorology or share market or real estate to name a few. For example, a
meteorologist can exchange weather data by using his/her own tags like
<humidity>, <temperature>, <rainfall> etc. These tags can be
filed in corresponding templates. Such web pages could directly be processed by
XML compatible applications. That is how the weather data could be
automatically evaluated through the web. This process makes it unnecessary to
agree upon a syntax resembling Document Type Definition (DTD) by the user
group.
The flexibility in the use of XML makes it so popular
in data exchange format and has made it extremely easy to format data using
your own tag. Now, the transfer of data becomes easy as these tags are humanly
readable and applicable in their own specific field. XML structure is being
used more and more for transporting data by people from all fields in relation
to prices or date information or author and many others.
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