Extensible Markup Language (XML) is a very simple and flexible text format derived from SGML. A complete XML-explanation is given below.
Originally designed to meet challenges of large scale electronic publishing. XML is playing an important role in exchanging wide variety of data on the web.
Hypertext Markup Language, popularly known as HTML is well known to most of us. It is probably the first lesson taught to any guy who aspires getting into the field of web development. But XML, although high relevant to the web, has not gained awareness to great extent.
To keep things simple and digestible, here is an in-depth brief-up of XML, explaining its meaning, basic purpose and relevance to the web. Take a look.
What is XML
eXtensible Markup Language, abbreviated as XML, is a markup language which is meant for the purpose of presenting structured documents over the web. XML, although similar in few aspects to HTML, differs from the fixed and defined nature of HTML tag sets.
In HTML, tag semantics are standard and well defined and therefore can’t be customized at all. For instance, a <body> tag has a defined meaning and the tag <product.name> has got no meaning.
In case of XML, tags can be customized as per the nature and information stored in the document. In simpler words, XML is meant to encode text and data, to make it simpler and more interpretable to humans as well as machines/applications.
Where does it belong to
XML is an application profile of Standard Generalised Markup Language(SGML). To give a brief-up overview about SGML, it is a prevalent web standard for the purpose of maintaining repositories of structured documents. SGML is not preferred for serving documents over the web due to inefficiency issues and therefore , XML, being a subset of SGML, is used for this purpose.
Why XML
We already have HTML (and even HTML5) to create webpages for publishing information on web so one might wonder if XML is a replacement of HTML or otherwise. It is important to understand here that XML was created so as to serve richly structured documents over the internet. The existing options, namely HTML and SGML, due to customization and efficiency issues, were not practical for this purpose.
An example
Below is a basic example of an encoded XML document, which is interpretable because of the use of customized tags.
<?xml version=”1.0″?>
<notice>
<to>Peter</to>
<from>XYZ Ltd</from>
<heading>Violation of official policy</heading>
<body>You are required to produce all the official documents to CEO by tomorrow</body>
</note>
For detailed insight into XML specifications, we recommend looking at this documentation here.