Introduction to XML

Pre Knowledge Required

HTML
JavaScript

About XML

XML stands for Extensible Markup Language. It is a markup language much like HTML. It was designed to carry data, not to display data. XML tags are not predefined, you must define your own tags. It is designed to be self-descriptive language and it is a W3C Recommendation language. XML make exchange of data on the web much easier and more efficient, by allowing developer to write their own Document Type Definition (DTD). These DTDs describe specific kinds of contents. XML is a simple and very flexible language based on SGML (Standard Generalized Markup Language) so its name as extensible markup language. XML is markup language so it can be run on any platform or any operating system or any environments. The evaluation of xml started back in 1996 and specification published in November 1996. XML 1.0 recommendations was published in February 1998. XML can used to create your own set of tags that give information about information. XML information stored in two of following ways.

Features of XML

XML support all features of HTML and SGML. XML is case-sensitive i.e. <name> is different from <NAME>. There are be only one root tag as data is organized in a hierarchical fashion. main feature-

1.Coding - XML based on Unicode.

2. Container tag- XML allows user defined tags but they must be container tags elements that have a single tag i.e. without a matching tag. These tags must end with a ' / '. example <name/>.

3. Modularity- HTML has no DTDs, SGML has limitless DTDs but these are only one for each type of documents. XML enables multiple DTDs on one document or single DTD for multiple documents.

4. Extensibility - XML powerful linking mechanism allows us to link to material without requiring the link forget to physically present in the object.

5. Distribution - XML supports composite documents i.e. documents composed of fragments of other documents that are automatically assembled to form that is displayed at that particular movement.

Limitation of XML

Maybe it is a little hard to understand, but XML does not DO anything. XML was created to structure, store and transport the information or data. The following example is a note to 'Sandeep' from 'Suman', stored as XML:

<note>
    <to>Sandeep</to>
    <from>Suman</from>
    <heading>Remind Me</heading>
    <body>This is body</body>
</note>

In the note tag above is quite self descriptive. It has sender and receiver information, it also has a heading and a message body. But still, this XML document does not DO anything. It is just pure information wrapped in tags. Someone must write a piece of software to send, receive or display it.