X/Open group (also known as the Open Group for Unix Systems[1][2] and incorporated in 1987 as X/Open Company, Ltd.[3][4]) was a consortium founded by several European UNIX systems manufacturers in 1984[3][5] to identify and promote open standards in the field of information technology. More specifically, the original aim was to define a single specification for operating systems derived from UNIX, to increase the interoperability of applications and reduce the cost of porting software. Its original members were Bull, ICL, Siemens, Olivetti, and Nixdorf—a group sometimes referred to as BISON.[6] Philips and Ericsson joined in 1985,[6] at which point the name X/Open was adopted.

The group published its specifications as X/Open Portability Guide, starting with Issue 1 in 1985, and later as X/Open CAE Specification.

In 1987, X/Open was incorporated as X/Open Company, Ltd.[3][4]

By March 1988, X/Open grew to 13 members: AT&T, Digital, Hewlett-Packard, Sun Microsystems, Unisys, NCR, Olivetti, Bull, Ericsson, Nixdorf, Philips, ICL, and Siemens.[7]

By 1990 the group had expanded to 21 members:[8] in addition to the original five, Philips and Nokia from Europe; AT&T, Digital, Unisys, Hewlett-Packard, IBM, NCR, Sun, Prime Computer, Apollo Computer from North America; Fujitsu, Hitachi, and NEC from Japan; plus the Open Software Foundation and Unix International.

In October 1993, a planned transfer of UNIX trademark from Novell to X/Open was announced;[9] it was finalized in 2nd quarter of 1994.[10]

In 1994, X/Open published the Single UNIX Specification, which was drawn from XPG4 Base and other sources.[11]

In 1996, X/Open merged with the Open Software Foundation to form The Open Group.[5][3]

X/Open was also responsible for the XA protocol for heterogeneous distributed transaction processing, which was released in 1991.[12]

X/Open Portability Guide

X/Open published its specifications under the name X/Open Portability Guide (or XPG). Based on the AT&T System V Interface Definition,[13] the guide has a wider scope than POSIX, which is only concerned with direct operating system interfaces. The guide specifies a Common Application Environment (CAE) intended to allow portability of applications across operating systems. The primary aim was compatibility between different vendors' implementations of UNIX, though some vendors also implemented the standards on non-UNIX platforms.

Issue 1 of the guide covered basic operating system interfaces, the C language, COBOL, indexed sequential file access method (ISAM) and other parts[14] and was published in 1985.[15] Issue 2 followed in 1987,[15] and extended the coverage to include Internationalization, Terminal Interfaces, Inter-Process Communication, and the programming languages C, COBOL, FORTRAN, and Pascal, as well as data access interfaces for SQL and ISAM.[16] In many cases these were profiles of existing international standards. Issue 3 (XPG3) followed in 1989,[15] its primary focus being convergence with the POSIX operating system specifications; it added Window Manager, ADA Language and more.[17] Issue 4 (XPG4) was published in July 1992. The Single UNIX Specification was based on the XPG4 standard. The XPG3 and XPG4 standards define all aspects of the operating system, programming languages and protocols which compliant systems should have.

Multiple levels of compliance and corresponding labels were available, depending on the scope of the guide that was covered: Base and Plus; labels Component and Application are for SW components and applications that make use of the portability guide.[18]

Issue 1 was published as a single publication with multiple parts, ISBN 0-444-87839-4.

Issue 2 was published in multiple volumes:

Issue 3 was published in multiple volumes:

The XPG4 Base specification includes the following documents:

The above three documents were published not under the label X/Open Portability Guide but rather as CAE Specification.[15] Nonetheless, the term X/Open Portability Guide, Issue 4 sees some use in reference to 1992 year of publication.[19][20]

Further X/Open publications under the label X/Open CAE Specification rather than X/Open Portability Guide:

See also


  1. ^ Kornel, Amiel (3 February 1986). "Unix advancing in drive toward European market acceptance". Computerworld. p. 51.
  2. ^ Sandholtz, Wayne (1992). "Spinoffs". High-Tech Europe: The Politics of International Cooperation. University of California Press.
  3. ^ a b c d "The Daemon, the GNU and the Penguin, Excursus: UUNET & Ch. 11". Groklaw. 2 June 2005.
  4. ^ a b McKinnon, Linda; McKinnon, Al (2004). Installing and Administering Linux. John Wiley & Sons. p. 5. ISBN 9780471453994.
  5. ^ a b "The UNIX System -- History and Timeline -- UNIX History". unix.org.
  6. ^ a b Tottenham, John (August 1987). "X/OPEN - What, Who, Why, When". Australian Unix systems User Group Newsletter. Vol. 8, no. 3–4. p. 158.
  7. ^ Ackerman Jr., Robert (March 21, 1988). "X/Open Makes Bid for Common Applications Environment". InfoWorld. Vol. 10, no. 12. p. S9.
  8. ^ Pasquali, Virgilio (Summer 2005). "ICL and Europe". RESURRECTION, the Bulletin of the Computer Conservation Society (35). ISSN 0958-7403. Contains more on history of X/Open.
  9. ^ Karish, Chuck (October 12, 1993). "The name "UNIX" is now the property of X/Open". Newsgroupcomp.std.unix.
  10. ^ "Frequently Asked Questions". unix.org.
  11. ^ "The Single UNIX Specification". unix.org.
  12. ^ Kleppmann, Martin (April 2, 2017). Designing Data-Intensive Applications (1 ed.). O'Reilly Media. p. 361. ISBN 978-1449373320.
  13. ^ Libes, Don; Ressler, Sandy (1989). Life With UNIX: A Guide For Everyone. Prentice Hall. p. 74. Bibcode:1989lwug.book.....L. ISBN 978-0135366578.
  14. ^ X/Open Portability Guide, issue 1. Elsevier. July 1985. ISBN 0444878394.
  15. ^ a b c d Referenced Documents. ((cite book)): |work= ignored (help)
  16. ^ Marshall, Martin (September 19, 1988). "X/Open Verification Branding Is Established". InfoWorld. Vol. 10, no. 38. p. 42.
  17. ^ Marshall, Martin (May 29, 1989). "X/Open Seeks Accord Between OSF, UII, Japan". InfoWorld. Vol. 11, no. 22. p. 41.
  18. ^ Cox, John (September 19, 1988). "X/Open to make mark". Network World. Vol. 5, no. 38. p. 59.
  19. ^ Standards Conformance Guide (PDF). Sun Microsystems. November 1995.
  20. ^ Seebach, Peter (2010). Beginning Portable Shell Scripting: From Novice to Professional. Apress. p. 163. ISBN 978-1-4302-1044-3.
  21. ^ Distributed Transaction Processing: The XA Specification (PDF). X/Open Company. December 1991. ISBN 1-872630-24-3. ((cite book)): |website= ignored (help)}
  22. ^ Systems Management: Management Protocol Profiles (XMPP) (PDF). X/Open Company. October 1993. ISBN 1-85912-018-0. ((cite book)): |website= ignored (help)
  23. ^ X/Open DCE: Remote Procedure Call (PDF). X/Open Company. August 1994. ISBN 1-85912-041-5. ((cite book)): |website= ignored (help)
  24. ^ X/Open CAE Specification System Interface Definitions, Issue 4, Version 2 (PDF). X/Open Company. September 1994. ISBN 1-85912-036-9. ((cite book)): |website= ignored (help)
  25. ^ X/Open CAE Specification System Interfaces and Headers, Issue 4, Version 2 (PDF). X/Open Company. September 1994. ISBN 1-85912-037-7. ((cite book)): |website= ignored (help)
  26. ^ X/Open CAE Specification Commands and Utilities, Issue 4, Version 2 (PDF). X/Open Company. September 1994. ISBN 1-85912-034-2. ((cite book)): |website= ignored (help)
  27. ^ X/Open CAE Specification Networking Services, Issue 4 (PDF). X/Open Company. September 1994. ISBN 1-85912-049-0. ((cite book)): |website= ignored (help)
  28. ^ Data Management:SQL Call Level Interface (CLI) (PDF). X/Open Company. March 1995. ISBN 1-85912-081-4. ((cite book)): |website= ignored (help)
  29. ^ File System Safe UCS Transformation Format (UTF-8) (PDF). X/Open Company. March 1995. ISBN 1-85912-082-2. ((cite book)): |website= ignored (help)
  30. ^ Distributed Transaction Processing: The TX (Transaction Demarcation) Specification (PDF). X/Open Company. April 1995. ISBN 1-85912-094-6. ((cite book)): |website= ignored (help)
  31. ^ X.25 Programming Interface using XTI (XX25) (PDF). X/Open Company. November 1995. ISBN 1-85912-136-5. ((cite book)): |website= ignored (help)
  32. ^ Distributed Transaction Processing: The TxRPC Specification (PDF). X/Open Company. November 1995. ISBN 1-85912-115-2. ((cite book)): |website= ignored (help)
  33. ^ Distributed Transaction Processing: The XATMI Specification (PDF). X/Open Company. November 1995. ISBN 1-85912-130-6. ((cite book)): |website= ignored (help)
  34. ^ Distributed Transaction Processing: The XCPI-C Specification Version 2 (PDF). X/Open Company. November 1995. ISBN 1-85912-135-7. ((cite book)): |website= ignored (help)
  35. ^ X/Open Curses, Issue 4. X/Open Company. 1995. ISBN 9781859120774.
  36. ^ X/Open Curses, Issue 4, Version 2 (PDF). X/Open Company. 1996. ISBN 1-85912-171-3. ((cite book)): |website= ignored (help)
  37. ^ Data Management: Structured Query Language (SQL) Version 2 (PDF). X/Open Company. March 1996. ISBN 1-85912-151-9. ((cite book)): |website= ignored (help)