Extensible Markup Language

XML is the acronym of Extensible Markup Language. This means that:

• XML is a formal language. This means XML is defined by a set of formal rules (a grammar) that say exactly how to compose an XML document.
• XML allows to markup your data. Data is included in XML documents as strings of text and is surrounded by text markup that describes the data.
• XML is extensible. The language allows an extensible set of markup tags that can be adapted to meet many different needs.

XML is simply a flexible format to mark up data with human-readable tags. It is worth stressing that an XML document is a text document and can be read and modified with any text editor. In particular, XML is not a:

• presentation language like HTML. XML markup defines the meaning of the data. It says nothing about the style of the data.
• programming language like Java. An XML document does not compute anything.
• network transport protocol like HTTP. XML does not transfer data across the network.
• database management system like Oracle. XML does not store and retrieve data.