Extensible Markup Language (XML) is an ISO compliant subset of SGML, a simple
coding language using generic semantics that are suitable for representing information
from a wide range of sources. XML is extensible, it allows one to write a Document
Type Definition (DTD) and define the rules of the language so the receiver agent
can interpret the document. The aim of XML is to provide an easy to use subset
of SGML that permits custom tags to be processed. Custom tags will enable the
definition, transmission and interpretation of data structures between organisations.
Like HTML, XML uses these tags to describe content and data . However, rather than concentrating on the presentation of data, the tags in XML describe the meaning and structure of data very much like a database. This functionality allows for the complicated data types that are required for economical data interchange between different applications and systems. Furthermore, because XML enables separation of content and presentation, the content, or data, is portable across systems.
The XML syntax uses start and end tags such as <tag> and </tag> to identify information. Data delimited by tags is called an element. Every XML document has a single root element, which is the top-level element that contains all the other elements. An element can also have attributes, made up as name-value pairs, that are part of the element and are used for further definition.
XML uses XSLT (Extensible Style-sheet Language Transformations) to present data to different clients, and can be combined with CSS.
The main benefits of XML are:
Having covered the main mark-up languages it is time to move on to the scripting
languages, which are divided into two parts; client side and server side. So
lets start with Client Side Scripting