Editing Videotex (section)

== Standards ==
Work to establish an international standard for videotex began in 1978 in [[CCITT]]. But the national delegations showed little interest in compromise, each hoping that ''their'' system would come to define what was perceived to be going to be an enormous new mass-market. In 1980 CCITT therefore issued recommendation S.100 (later T.100),<ref>ITU-T Recommendation T.100, [http://www.itu.int/rec/dologin_pub.asp?lang=e&id=T-REC-T.100-198811-I!!PDF-E&type=items International Information Exchange for International Videotex], Geneva, 1980; amended Malaga 1984<!-- alternate link: http://eu.sabotage.org/www/ITU/T/T0100e.pdf--></ref> noting the points of similarity but the essential incompatibility of the systems, and declaring all four to be recognised options.

Trying to kick-start the market, [[AT&T Corporation]] entered the fray, and in May 1981 announced its own Presentation Layer Protocol (PLP).<ref>[https://books.google.com/books?id=79YSr96pZsQC&pg=PA539 Bye-bye Buzby, bye-bye], ''[[New Scientist]]'', 28 May 1981</ref><ref>[https://books.google.com/books?id=Kj0EAAAAMBAJ&pg=PA33 Special Section: Videotex arrives in America], ''[[InfoWorld]]'', 28 September 1981, pp. 33–54. For AT&T's PLP, see especially p. 38 and pp. 41–42</ref> This was closely based on the Canadian Telidon system, but added to it some further graphics primitives and a syntax for defining [[macro (computer science)|macro]]s, algorithms to define cleaner pixel spacing for the (arbitrarily sizeable) text, and also dynamically redefinable characters and a mosaic block graphic character set, so that it could reproduce content from the French Antiope.  After some further revisions this was adopted in 1983 as [[ANSI]] standard X3.110, more commonly called [[NAPLPS]], the North American Presentation Layer Protocol Syntax.  It was also adopted in 1988 as the presentation-layer syntax for [[NABTS]], the North American Broadcast Teletext Specification.

Meanwhile, the European national [[Postal Telephone and Telegraph]] (PTT) agencies were also increasingly interested in videotex, and had convened discussions in [[European Conference of Postal and Telecommunications Administrations]] (CEPT) to co-ordinate developments, which had been diverging along national lines.  As well as the British and French standards, the Swedes had proposed extending the British Prestel standard with a new set of smoother mosaic graphics characters; while the specification for the proposed German [[Bildschirmtext]] (BTX) system, developed under contract by [[IBM]] Germany for [[Deutsche Bundespost]], was growing increasingly baroque. Originally conceived to follow the UK Prestel system, it had accreted elements from all the other European standards and more.  This became the basis for setting out the [[CEPT Recommendation T/CD 06-01|CEPT recommendation T/CD 06-01]],<ref>[https://books.google.com/books?id=Y_ZOoWgEMvgC&pg=PA400 The viewdata war is over], ''[[New Scientist]]'', 14 May 1981</ref><ref>ETS 300 072, [http://www.etsi.org/deliver/etsi_i_ets/300001_300099/300072/01_60/ets_300072e01p.pdf Terminal Equipment: Videotex presentation layer protocol: Videotex presentation layer data syntax], November 1990.  Updated version of CEPT Recommendation T/CD 06-01.</ref> also proposed in May 1981.

However, due to national pressure, CEPT stopped short of fixing a single standard, and instead recognised four "profiles": 
*[[CEPT1]], corresponding to the German ''BTX''; 
*[[CEPT2]], the French ''Minitel''; 
*[[CEPT3]], the British ''Prestel''; 
*[[CEPT4]], the Swedish ''Prestel Plus''.

National videotex services were encouraged to follow one of the existing four basic profiles; or if they extended them, to do so in ways compatible with a "harmonised enhanced" specification.  
There was talk of upgrading Prestel to the full CEPT standard "within a couple of years".  But in the event, it never happened.  The German BTX eventually established CEPT1; the French Minitel continued with CEPT2, which was ready to roll out; and the British stayed with CEPT3, by now too established to break compatibility.

The other countries of Europe adopted a patchwork of the different profiles.<ref>e.g. [http://eur-lex.europa.eu/LexUriServ/LexUriServ.do?uri=COM:1993:0156:FIN:EN:PDF Main events and developments in the electronic information services market 1991], [[European Commission]] report COM(93) 156. See table 14, page 30 (folio 39 of the pdf)<!-- alternative url: http://aei.pitt.edu/4772/01/000916_1.pdf --></ref>

In later years, CEPT fixed a number of standards for extension levels to the basic service: for photographic images (based on [[JPEG]]; T/TE 06-01, later revisions), for alpha-geometric graphics, similar to NAPLPS/Telidon (T/TE 06-02),<ref>ETS 300 073, [http://www.etsi.org/deliver/etsi_i_ets/300001_300099/300073/01_60/ets_300073e01p.pdf Videotex presentation layer data syntax: Geometric Display]. Equivalent to CEPT Recommendation T/TE 06-02 (Edinburgh, 1988)</ref> for transferring larger data files and software (T/TE 06-03),<ref>ETS 300 074, [http://www.etsi.org/deliver/etsi_i_ets/300001_300099/300074/01_60/ets_300074e01p.pdf Videotex presentation layer data syntax: Transparent Data]. Equivalent to CEPT Recommendation T/TE 06-03 (Edinburgh, 1988)</ref> for active terminal-side capabilities and scripting (T/TE 06-04),<ref>ETS 300 075, [http://www.etsi.org/deliver/etsi_i_ets/300001_300099/300075/01_60/ets_300075e01p.pdf Videotex processable data]. (1990). Based on CEPT Recommendation T/TE 06-04. [http://www.etsi.org/deliver/etsi_i_ets/300001_300099/300075/02_60/ets_300075e02p.pdf Second edition, 1994]</ref> and for discovery of terminal capabilities (T/TE 06-05).<ref>ETS 300 076, [http://www.etsi.org/deliver/etsi_i_ets/300001_300099/300076/01_60/ets_300076e01p.pdf Videotex Terminal Facility Identifier]. (1990). Based on CEPT Recommendation T/TE 06-05.[http://www.etsi.org/deliver/etsi_i_ets/300001_300099/300076/02_60/ets_300076e02p.pdf Second edition, 1992]. [http://www.etsi.org/deliver/etsi_i_ets/300001_300099/300076/03_60/ets_300076e03p.pdf Third edition, 1994].</ref> But interest in them was limited.

CCITT T.101<ref>ITU-T Recommendation T.101, [http://www.itu.int/rec/dologin_pub.asp?lang=e&id=T-REC-T.101-198811-S!!PDF-E&type=items International interworking for Videotex services] Version of 1988; [http://www.itu.int/rec/dologin_pub.asp?lang=e&id=T-REC-T.101-199411-I!!ZPF-E&type=items Expanded version, 1994]</ref>