Extensible Markup Language (XML)

XML “describes a class of data objects called XML documents and partially describes that the behavior of computer programs that process them.” [23] This definition with its literal meaning does not do justice to XML when we consider its place in today’s Internet and the world of information technologies. However, it is the simplicity of its design that brings such fame to XML. We owe this simplicity to its design goals: [23]

1. Straightforward to use over the Internet.
2. Support of a wide variety of applications.
3. Compatibility with SGML.
4. Easy to write programs that process XML documents.
5. The number of optional features in XML be kept to the absolute minimum, ideally zero.
6. XML documents be human-legible and reasonably clear.
7. Modeling XML document structure be easy.
8. The design of XML be formal and concise.
9. XML documents be easy to create.
10. Terseness in XML markup be of minimal importance.

In the following sections, we look at the XML usage in different application areas
where XML serves as a metadata definition language or a data container whether systems be designed intentionally as such or not.