XML has been around since 1998. It is based on Standard Generalized Markup Language (SGML), which in turn was created out of General Markup Language (GML) in the 1960s. XML is actually a simplified version of SGML.
SGML describes how to write languages, specifically those that work with text in electronic documents. SGML is also an international standardISO 8879. Interestingly enough, SGML was one of the considerations for HTML when it was first developed.
The first XML recommendation was released in February 1998. Since then, XML has increased in popularity, and its now a worldwide standard for sharing information. Human beings, databases, and many popular software packages all use XML documents to store and share information. Web services also use an XML format to share information over the Internet.
The W3C developed the XML specification. This organization also works with other recommendations such as HTML and XHTML. Detailed information about the XML specification is available at the W3Cs website at www.w3c.org/XML/. At the time of writing, the current specification was for XML 1.1. You can view this specification at www.w3.org/TR/2004/REC-xml11-20040204/.
When it created XML, the W3C published the following goals at www.w3.org/TR/REC-xml/#sec-origin-goals:
XML shall be straightforwardly usable over the Internet.
XML shall support a wide variety of applications.
XML shall be compatible with SGML.
It shall be easy to write programs which process XML documents.
The number of optional features in XML is to be kept to the absolute minimum, ideally zero.
XML documents should be human-legible and reasonably clear.
The XML design should be prepared quickly.
The design of XML shall be formal and concise .
XML documents shall be easy to create.
Terseness in XML markup is of minimal importance.
In other words, XML should be easy to use in a variety of settings, by both people and software applications. The rules for XML documents should be clear so they are easy to create.
So how do we create XML documents?