1、CEPT T/SF*S*E 91 D 232b414 0012705 3T5 W T/SF 59 E Page1 Recommendation T/SF 59 (Copenhagen 1987, revised io Madrid 1991) INTERNATIONAL VIDEOTEX SERVICE Recommendation proposed by Working Group T/WG 7 “Services and facilities” (SF) Text of the Recommendation adopted by the Commercial action committe
2、e (CAC) : “The European Conference of Posts and Telecommunications Administrations, considering - that in many European countries public Videotex Services already exist or are being established, - that ETS 300072 of ETSI defines a common European Videotex presentation data syntax, - that CCITT Recom
3、mendation F.300 describes the superset of characteristics and functions of international - that there is a demand for international access to public Videotex SeMces, recommends that the following regulations be followed in providing the international Videotex Service.” Videotex Services, Note. In so
4、me cases, the network operators may also be Administrations. Edition of August 20, 1991 T/SF 59 E Page 2 I 1.1. Videotex Services I The functionalities and facilities of the Videotex Services as seen from the user are: - connection to databases with various applications, - connection to the internat
5、ional service, - billing capabilities, - dialogue handling, I - directories, I - transaction, I I - information retrieval, - Videotex message service. - data processing, - terminal-to-terminal messaging (conferencing), - interworking with other Telematic services, - program and data downloading, - t
6、erminal identification, - user identification, - closed user groups. These lists are not exhaustive. The following list of functionalities may be required and/or offered by some Videotex Services: Contents PSTN 1. Introduction 2 2. Definitionofterms. . 3 3. Functionalities of the Service . 6 4. Inte
7、rnational interworking of Videotex Services . 11 5. Interworking with other Telematic Services . 19 6. Customer Information/Directories . 21 7. Quality of Service 21 Videotex Service Centre 1. INTRODUCTION This Recommendation describes the set of mandatory and optional functions of the European Vide
8、otex Services. Edition of August 20, 1991 CEPT T/SF*59*E 71 = 2326VL4 0012707 578 Videotex Access PSTN Point PDN 2. Videotex Host Computer 2.1. 2.1.1. Videotex Service PSTN Centre PDN - 2.1.2. 2.1.3. Videotex Host Computer T/SF 59 E Page 3 (d) Other configurations may exist, replacing PSTN by ISDN,
9、PDN by leased lines etc. DEFINITION OF TERMS Videotex Service General A Videotex Service is an interactive service which provides, through appropriate access by standardized procedures, for users of Videotex terminals to communicate with data bases via telecommunication networks. A Videotex Service
10、includes a set of the following characteristics: 1. information is generally in an alphanumeric and/or pictorial form, 2. information is stored in data bases, 3. information is transmitted between the data base and users by telecommunication networks, 4. displayable information is presented on a sui
11、tably modified television receiver or other visual display 5. access is under the users direct or indirect control, 6. the service is easily operated by the general public as well as specialist users, i.e. the service is user-friend- 7. the service provides facilities for users to create and modify
12、information in the data bases, 8. the service provides data base management facilities which allow application providers to create, Videotex Service projle The set of functionalities required by a Videotex Service. It includes the service, application and presentation functionalities. Videotex appli
13、cation Part of a Videotex Service which is under the responsibility of only one application provider. The Videotex Service provider may also act as an application provider. device, IY, maintain and manage data bases and to manage closed user groups facilities. Edition of August 20, 1991 CEPT T/SF*57
14、*E 92 232b4L4 0022708 404 T/SF 59 E Page 4 I 2.2. 2.2.1. 2.2.2. 2.2.3. 2.2.4. 2.2.5. 2.2.6. 2.2.7. 2.2.8. Videotex Service facilities General A Videotex Service facility is an application layer implementation in a Videotex Service, providing a specific, clearly defined facility to Videotex users. A
15、Videotex Service provides users with a number of such service facilities. Videotex information retrieval A Videotex Service facility in which a user obtains information by means of a dialogue with a data base. Videotex transaction A Videotex Service facility which allows users to create and/or modif
16、y information stored in a data base. Access to these facilities will generally require special functions and procedures to authenticate the authority to access. This service facility includes, but is not limited to, transactions leading to or influencing a commercial relationship between users and a
17、pplication providers. Videotex messaging A Videotex Service facility which allows users to communicate with each other by storing messages in a commonly accessible data base. These stored messages may either be retrieved by the user or delivered automatically. Videotex terminal-to-terminal messaging
18、 (conferencing) A Videotex Service facility which, by providing routing and switching functions, enables users to send and receive messages in a conversational manner. This does not preclude direct terminal-to-terminal messaging using existing networks. Videotex data processing A Videotex Service fa
19、cility which allows the user to employ processing and storage capacity at the host computer. Videotex downloading A Videotex Service facility which allows a host computer to deliver a program and/or data to a Videotex terminal in order to have it processed in this equipment. Videotex cost limit A vi
20、deotex service facility that allows to set limits on the costs incurred by the usage of the videotex service. The limit can be set either by the user or by a service provider. Limits may apply to: - single items like one frame or one transaction, - levels of time-based charges, - the accumulated sum
21、 of communication and/or application charges. The limit may be set for only one or for any combination of them. Whenever a limit is reached, one of two mechanisms may be activated: - warning limits: the users attention is drawn to the fact that the indicated limit will be exceeded; - blocking limit:
22、 the user is not allowed to spend more than is indicated by the limit. 2.3. Participants in Videotex Semce 2.3.1. Videotex Service provider 2.3.2. Videotex application provider A party responsible to the user for the provision and operation of a Videotex Service. A party responsible by agreement wit
23、h a Videotex Service provider for providing information or transaction facilities to Videotex Service users. The application provider may or may not operate the host computer on which the application is provided. Applications are provided by means of the service providers host computer). Application
24、s are provided by means of host computers not operated by the service provider. A party responsible by agreement with a Videotex Service provider for providing telecommunication services for interconnecting user terminals, application provider equipment and/or Videotex host computers. 2.3.2.1. Inter
25、nal Videotex application provider 2.3.2.2. External Videotex application provider 2.3.3. Videotex communications network provider Edition of August 20, 1991 CEPT T/SF*59*E 91 232b414 0022709 340 O 2.3.4. 2.3.5. 2.4. 2.4.1. 2.4.2. 2.4.3. 2.4.4. 2.4.5. 2.4.6. 2.4.7. 2.4.8. 2.4.9. T/SF 59 E Page 5 Vide
26、otex user A person who, by means of a Videotex terminal, uses the Videotex Service. Videotex closed user group A group of users who are allowed access to applications or other Videotex Service facilities that are not available to other users. Videotex systems General A Videotex system is the hardwar
27、e and software used to implement a Videotex Service. Videotex terminal The equipment by mens of which the user interacts with the Videotex Service. A typical Videotex terminal includes : 1. a numeric keypad and/or alphanumeric keyboard and/or other graphical input devices; 2. a visual display unit;
28、3. electronic processing and storage devices required to interface these components to the telecommunica- The terminal may also provide a direct terminal-to-terminal capability, and may include other components such as a hard copy output unit, magnetic or optical storage devices, and additional proc
29、essing and/or storage devices. Videotex userlterminal identification facility A facility which allows the Videotex system to distinguish between authorized and non-authorized access to a Videotex Service or certain applications of this service, e.g. messaging, closed user groups and billing. There a
30、re three types of identification: - identification of the terminal, - identification of the user, - identification of the line. Videotex Service centre A computer system used by the Videotex Service provider to authorize access to a Videotex Service. Other functions of the service centre may include
31、 assistance to users in selecting the particular application required (either provided by the Service centre or by other host computers), as well as management facilities such as billing, statistics gathering, etc. The same computer may also be a host computer and/or provide a gateway function. Vide
32、otex data base A set of information and/or transaction facilities that can be accessed by, or made available to, users. Videotex host computer The computer or network of computers provided by a single party on which one or more applications are managed and/or one or more other Videotex Service facil
33、ities are provided. External Videotex host computer A host computer not operated by the service provider. Videotex gateway A function of a computer providing access to data base(s) of other computer(s). This may include protocol selection and/or protocol conversion and/or dialogue handling functions
34、. In addition, the gateway is the point where the administrative data for the international Videotex Service are handled, such as the data for the international accounting, billing information in case of frame/application or additional communica- tion charges, the information about the subscriber st
35、atus in case of message service and service data concerning the service profiles or terminal profiles. The gateway can also give access to the directory of Videotex Services available in the foreign country. In order to provide these functions in the international service, a gateway is connected to
36、a gateway in the corresponding country. Videotex access point (VAP) A function providing access to Videotex host computers, protocol conversion for layers 1-3, management facilities such as billing, statistics gathering and dialogue handling capabilities. In general case it does not support Videotex
37、 applications. tions network and to generate the display. Edition of August 20, 1991 I CEPT T/SF*5*E 93 D 232b434 0032730 Ob2 - T/SF 59 E Page 6 2.4.10. 2.4.11. 2.4.12. 2.4.13. 2.4.14. 3. 3.1. 3.1.1. 3.1.2. 3.1. 3.1.4. 3.2. Videotex interface unit (VIU) A function providing access to Videotex host c
38、omputers, protocol conversion for layers 4-7 and/or data syntax conversion and optionally protocol conversion for layers 1-3 (PAD). It also handles some adminis- trative tasks such as billing for the conversion charges and communication network charges. A Videotex interface unit is typically used be
39、tween a terminal and a Videotex Service where conversion facilities are required. Videotex Service unit (VSU) It is a VIU with additional functions of handling application charges and accounting, and may also provide user authorization and/or identification. Videotex frame The information that is re
40、trieved by a single user function from a terminal and presented as a complete entity (full screen contents or parts of the screen, e.g. areas on the screen) by the terminal, but may include information that requires scrolling before it is displayed and may include dynamic effects such as overwrit- i
41、ng. Local user action may take place within a frame. Videotex page An organized set of one or more frames. Videotex system jeld A data collection field in which predefined type of data is filled in by the Videotex service or by the user. FUNCTIONALITIES OF THE SERVICE General Paragraph 3. describes
42、the various facilities that may be used to convey the information by the Videotex service. Those facilities are listed below for the service, the application and the presentation. In order to ensure non-obsolescence of the data bases, and to permit international exchange of data, a range of service
43、profiles will be defined. They will allow the comparison of the service profile(s) adopted in preparing an application and the service profile assumed by the user. It is then possible to determine whether or not the user can interact with the application or whether the data must be transcoded or whe
44、ther the terminal or application adapted. The transcoding process may take place at an intermediate point in the international Videotex service. This may be decided by a negotiation phase in the call establishment. When information is prepared according the set of functionalities common to ail three
45、 presentation profiles no loss of information will occur when transcoding is applied. Applications may require knowledge of the service profile assumed by the user in order to exercise discretion in limiting access to data when displayed information may not convey the complete meaning of the applica
46、tion due to the absence of the application, presentation or session functions of the service profile. Videotex services use different keying sequences and visual identifiers for the different service functions and dialogue functions. Harmonization is considered important but for further study. Servi
47、ce functions These functions may be used within the service, according to implementation. From the user point of view they are selected by routing to or selecting an appropriate point in the Videotex service: a) Function Vi : Select an application on a Videotex service (containing an identification
48、of the applica- b) Function V2: Leave the application and return to the first effective choice of the national Videotex c) Function V3: Return to the first effective choice of the remote Videotex service. d) Function V4: Leave the current application and return to the point where this application wa
49、s selected. e) Function V5: Provide billing information. f) Function V6: Leave the Videotex service. g) Function V7: Request service/application identification. tion). service. Edition of August 20, 1991 CEPT T/SF*59*E 91 = 232brlLrl OOL27LL TT9 I 3.3. 3.4. 3.4.1. 3.4.1.1. 3.4.1.2. 3.4.1.3. 3.4.1.4. T/SF 59 E Page 7 Dialogue functions The following functions may be used within the application to retrieve items of information (retrieval mode) or to collect data (data collection mode) and forward them to the application, according to implementation. a) Function D1: Declare valid
