Editing XML (section)

== Versions ==
=== 1.0 and 1.1 ===
The first (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.

The second (XML 1.1) was initially published on February 4, 2004, the same day as XML 1.0 Third Edition,<ref>{{cite web|editor1-first=T.|editor1-last=Bray|editor2-first=J.|editor2-last=Paoli|editor3-first=C. M.|editor3-last=Sperberg-McQueen|editor4-first=E.|editor4-last=Maler|editor5-first=F|editor5-last=Yergeau|publisher=W3C|title=Extensible Markup Language (XML) 1.0|edition=3rd|format=W3C Recommendation|url=https://www.w3.org/TR/2004/REC-xml-20040204|date=4 February 2004}}</ref> 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.{{sfnp|Bray|Paoli|Sperberg-McQueen|Maler|2006|loc=section 1.3}} The main changes are to enable the use of line-ending characters used on [[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 particular features.<ref>{{cite book|last=Harold|first=Elliotte Rusty|title=Effective XML|publisher=Addison-Wesley|year=2004|pages=[https://archive.org/details/effectivexml50sp00haro/page/10 10–19]|url=https://archive.org/details/effectivexml50sp00haro/page/10|isbn=0-321-15040-6|url-access=registration}}</ref>

Prior to its fifth edition release, XML 1.0 differed from XML 1.1 in having stricter requirements for characters available for use in element and attribute names and unique identifiers: in the first four editions of XML 1.0 the characters were exclusively enumerated using a specific version of the [[Unicode]] standard (Unicode 2.0 to Unicode 3.2.) The fifth edition substitutes the mechanism of XML 1.1, which is more future-proof but reduces [[Redundancy (information theory)|redundancy]]. The approach taken in the fifth edition of XML 1.0 and in all editions of XML 1.1 is that only certain characters are forbidden in names, and everything else is allowed to accommodate suitable name characters in future Unicode versions. In the fifth edition, XML names may contain characters in the [[Balinese script|Balinese]], [[Cham script|Cham]], or [[Phoenician alphabet|Phoenician]] scripts among many others added to Unicode since Unicode 3.2.{{sfnp|Bray|Paoli|Sperberg-McQueen|Maler|2006|loc=section 1.3}}

Almost any Unicode code point can be used in the character data and attribute values of an XML 1.0/1.1 document, even if the character corresponding to the code point is not defined in the current version of Unicode. In character data and attribute values, XML 1.1 allows the use of more [[control character]]s than XML 1.0, but, for "robustness", most of the control characters introduced in XML 1.1 must be expressed as numeric character references (and #x7F through #x9F, which had been allowed in XML 1.0, are in XML 1.1 even required to be expressed as numeric character references{{sfnp|Bray|Paoli|Sperberg-McQueen|Maler|2006|loc=section 1.3}}). Among the supported control characters in XML 1.1 are two line break codes that must be treated as whitespace characters, which are the only control codes that can be written directly.

=== 2.0 ===
There has been discussion of an XML 2.0, although no organization has announced plans for work on such a project. XML-SW (SW for [[Skunkworks project|skunkworks]]), which one of the original developers of XML has written,<ref>{{Cite web |first=Tim |last=Bray |url=http://www.textuality.com/xml/xmlSW.html |website=Textuality |title=Extensible Markup Language, SW (XML-SW) |date=10 February 2002}}</ref> contains some proposals for what an XML 2.0 might look like, including elimination of DTDs from syntax, as well as integration of [[XML namespace]]s, [[XML Base]] and [[XML Information Set]] into the base standard.

=== MicroXML ===
In 2012, [[James Clark (programmer)|James Clark]] (technical lead of the XML Working Group) and [[John W. Cowan|John Cowan]] (editor of the XML 1.1 specification) formed the MicroXML Community Group within the W3C and published MicroXML, a specification for a significantly reduced subset of XML.<ref>{{Cite web |date=2012-10-01 |title=MicroXML Community Group |url=https://www.w3.org/community/microxml/ |access-date=2023-08-05 |website=W3C |language=en-US}}</ref> MicroXML provides a much simpler core syntax by stripping away many features of full XML, such as document type declarations and CDATA sections,<ref name="quovadis"/> while ensuring XML namespace validity by disallowing names conflicting with namespace prefixing.

=== Binary XML ===
{{main article|Binary XML}}
Due to the verbosity of textual XML, various binary formats have been proposed as compact representations for XML: [[Fast Infoset]], based on [[ASN.1]], was published as an international standard by the [[ITU-T]] in 2005, and later by [[ISO]]. [[Efficient XML Interchange]] (EXI), a binary XML format originally developed by AgileDelta, was adopted as a W3C recommendation in 2011, with a second edition published in 2014.