XML

Chen Weixiang @ Apr 29, 2017 | TAG: Programming

This article introduce the Extensible Markup Language (XML).

Overview

Extensible Markup Language (XML) is a markup language that defines a set of rules for encoding documents in a format that is both human-readable and machine-readable. The W3C’s XML 1.0 Specification and several other related specifications — all of them free open standards — define XML.

The design goals of XML emphasize simplicity, generality, and usability across the Internet. It is a textual data format with strong support via Unicode for different human languages. Although the design of XML focuses on documents, the language is widely used for the representation of arbitrary data structures such as those used in web services.

Several schema systems exist to aid in the definition of XML-based languages, while programmers have developed many application programming interfaces (APIs) to aid the processing of XML data.

XML Recommendations

There are two current versions of XML.

  • XML 1.0

    XML 1.0 was initially defined in 1998. It has undergone minor revisions since then, without being given a new version number, and is currently in its fifth edition, as published on November 26, 2008. It is widely implemented and still recommended for general use.

  • XML 1.1

    XML 1.1 was initially published on February 4, 2004, the same day as XML 1.0 third edition, and is currently in its second edition, as published on August 16, 2006. It contains features (some contentious) that are intended to make XML easier to use in certain cases. The main changes are to enable the use of line-ending characters used on Extended Binary Coded Decimal Interchange Code (EBCDIC) platforms, and the use of scripts and characters absent from Unicode 3.2. XML 1.1 is not very widely implemented and is recommended for use only by those who need its unique features.

XML Syntax Quick Reference

XML Syntax Quick Reference

XML and HTML Comparison

XML and HTML were designed with different goals:

  • XML was designed to carry data: with focus on what data is
  • HTML was designed to display data: with focus on how data looks
  • XML tags are not predefined like HTML tags are

References