In computing, 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.
They provide a means for defining the structure, content and semantics of XML documents. XML Schema 1.0 was approved as a W3C Recommendation on and a second edition incorporating many errata was published on 28 October 2004; see reference list for pointers.RELAX NG Specification (errata), OASIS Committee Specification, 3 December 2001. Can be used as a library for validation and for accessing the schema. Definitive specification for RELAX NG using the XML syntax. The XML Schema Working Group, part of the XML Activity, is responsible for the W3C's work on this topic -- for details see the Working Group's charter.W3C Members can also participate in the W3C XML Schema Interest Group, a forum for the discussion of technical issues relating to the development of XML Schema.The RELAX NG specifications have been developed within OASIS by the RELAX NG Technical Committeee. RELAX NG is also an International Standard (ISO/IEC 19757-2). It is intended to be mostly compatible with XML Schema 1.0 and to have approximately the same scope, but also to fix bugs and make whatever improvements we can, consistent with the constraints on scope and compatibility.XML Schema 1.1 Part 2: Datatypes and XML Schema 1.1 Part 1: Structures are available.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-based formats have become the default for many office-productivity tools, including Microsoft Office (Office Open XML), Open and Libre Office (Open Document), and Apple's i Work. Apple has an implementation of a registry based on XML.