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A ''de facto'' standard is a custom, convention, product, or system that has achieved a dominant position by public acceptance or market forces (such as early entrance to the market). ''De facto'' is a Latin phrase that means ''in fact'' (literally by or from fact) in the sense of "in practice but not necessarily ordained by law" or "in practice or actuality, but not officially established", as opposed to ''de jure''. The term ''de facto'' standard is used in contrast with obligatory standards (also known as "''de jure'' standards"); or to express the dominant voluntary standard, when there is more than one standard available for the same use. In social sciences, a voluntary standard that is also a ''de facto'' standard is a typical solution to a coordination problem. The choice of a ''de facto'' standard tends to be stable in situations in which all parties can realize mutual gains, but only by making mutually consistent decisions. In contrast, an enforced "''de jure'' standard" is a solution to the prisoner's problem.〔 == Examples == A selection of well-known and illustrative examples of ''de facto'' and ''de jure'' standards: * with consolidation by tradition of use: * * The driver's seat side in a given country starts as a user/industry preference, turning to a local tradition, then a traffic code local norm. * * The QWERTY system was one of several options for the layout of letters on typewriter (and later keyboard) keys. It was developed to prevent adjacent keys from jamming on early and later mechanical typewriters, often attributed to the typist's speed.〔QWERTY〕 It became a ''de facto'' standard because it was used on the most commercially successful early typewriters. * * The ASCII text character set, standardized in 1963 is still in use. Document files containing ASCII usually have the TXT extension. * * The MP3 audio format started as an alternative to CD WAV (lossless format) for Internet music distribution, then replaced it — it is now supported by the vast majority of music players, audio transport, audio storage and noncommercial media. WAV and MP3 are also "''de jure'' ISO formats". * with consolidation by uniqueness and efficiency: * * HTML (computer file format) started as "''de facto''" (1993-1995) and became the "''de jure''" standard (1995–present day). * * PDF (computer file format) was first created in 1993 by Adobe. Adobe internal standards were part of its software quality systems, but they were neither published nor coordinated by a standards body. With the Acrobat Reader program available for free, and continued support of the format, PDF eventually became the ''de facto'' standard for printable documents. In 2005, PDF/A became a de jure standard as ISO 19005-1:2005.〔(【引用サイトリンク】title=ISO 19005-1:2005 - Document management -- Electronic document file format for long-term preservation -- Part 1: Use of PDF 1.4 (PDF/A-1) )〕 In 2008 Adobe's PDF 1.7 became ISO 32000-1:2008.〔(【引用サイトリンク】title=ISO 32000-1:2008 - Document management -- Portable document format -- Part 1: PDF 1.7 )〕〔(【引用サイトリンク】title=Adobe - Release PDF for Industry Standardization FAQ )〕 Examples of long-time ''de facto'' but never ''de jure'' standards (for computer file formats): * AutoCAD DXF: a ''de facto'' ASCII format for import and export of CAD drawings and fragments in the 1980s and 1990s. In the 2000s, XML based standards emerged as ''de facto'' standards. * Microsoft Word DOC (over all other old PC word processors): one of the best known ''de facto'' standards. Due to the market dominance of Word, it is supported by all office applications that intend to compete with it, typically by reverse engineering the undocumented file format. Microsoft has repeatedly internally changed the file specification between versions of Word to suit their own needs, while continuing to reuse the same file extension identifier for different versions. Other examples: *Most American-made spark plugs require a 13/16-inch socket to remove or install. * The 1/2-inch (12.7 mm) spacing of the rollers in a bicycle chain. * The IBM Personal Computer format, which used MS-DOS and Microsoft Windows operating systems, gained a large share of the personal computer market. Because of the great influence of the IBM PC on the personal computer market, competing products like the Rainbow 100 were eventually withdrawn. * Android (which is based on the Linux kernel and is currently developed by Google) is a standard in mobile operating systems. As of 2015, Android has the largest installed base of all operating systems of any kind. * Interpreted programming languages such as PHP that have multiple implementations tend to also have a ''de facto'' standard. In PHP's case the ''de facto'' standard is the binaries available from php.net, rather than the Phalanger implementation for example. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「De facto standard」の詳細全文を読む スポンサード リンク
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