1、- ITU-T RECMN*Fm300 (REV* information is stored in a data base; information is transmitted between the data base and users by telecommunication networks; displayable information is presented on a suitably modified television receiver or other visual display device; access is under the users direct o
2、r indiect control; the service is easily operated by the general public as well as specialist users, Le. the service is user- friendly; the service provides facilities for users to create and modiy information in the data bases: the service provides data base management facilities which allow inform
3、ation providers to create, maintain and manage data bases and to manage closed user group facilities; the service provides computer based applications, e.g., data processing, computer games. 5) 6) 7) 8) 9i 2.1.2 Videotex service profile The set of functionalities required by a Videotex service. It i
4、ncludes the service, application and presentation functionalities. Recommendation F.300 (03/93) 1 ITU-T RECMNMF.300 (REV*3) 73 El 4862573 0582374 438 W 2.1.3 Videotex application Part of a Videotex service which is under the responsibility of only one application provider. The Videotex Service provi
5、der may also act as an application provider. 2.2 Videotex service facilities 2.2.1 General A Videotex service facility is an application layer implementation in a Videotex service, providing a specific, clearly defined facility to Videotex users. Videotex service provides users with a number of such
6、 service facilities. 2.2.2 Videotex information retrieval A Videotex service facility in which a user obtains information by means of a dialogue with a data base. 2.2.3 Videotex transaction A Videotex service facility which allows users to create and/or modify information stored in a data base. Acce
7、ss to these facilities will generally require special functions and procedures to authenticate the authority to access. This service facility includes, but is riot limited to, transactions leading to or influencing a commercial relationship between users and application providers. 2.2.4 Videotex mes
8、saging 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. 2.2.5 Videotex conferencing A Videotex service facility which, by providi
9、ng 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. 2.2.6 Videotex data processing A Videotex service facility which allows the user to employ processing and s
10、torage capacity at the host computer. 2.2.7 Videotex telesoftware 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 Hi this equipment. 2.2.8 Videotex cost limit An optional Videotex service facility designed
11、 to protect the user or the concerned Videotex Service Provider(s) from incurring costs which exceed certain limits. The limit can be set either by the user or by a Videotex service provider. Limits may apply to: - - levels of time-based charges, - single items like one frame or one transaction, the
12、 accumulated sum 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;
13、 blocking limit: the user is not allowed to spend more than is indicated by the limit. 2 Recommendation F.300 (03/93) 23 Participants in Videotex service 23.1 Videotex service provider A party responsible to the user for the provision and operation of a Videotex service. 23.2 Videotex application pr
14、ovider A party responsible by agreement with a Videotex service provider for providing information or transaction facilities to Videotex service users. The information provider “ay or may not operate the host computer on which the application is implemented. 2.3.2.1 internal Videotex application pro
15、vider An application provider whose applications and/or whose facilities are provided by means of the service providers host computerk). 2.3.2.2 external Videotex application provider An application provider whose applications and/or whose facilities are provided by means of host computers not provi
16、ded by the service provider. 23.3 Videotex communications network provider A party responsible by agreement with a Videotex service provider for providing telecommunication services for interconnecting user terminals, application provider equipment andlor Videotex host computers. 2.3.4 Videotex user
17、 A person who, by means of a Videotex terminai, uses the Videotex service. 23.5 Videotex closed user group A group of users who are permitted access to applications or other Videotex service facilities that are not available to other users. 2.4 Videotex systems 2.4.1 General A Videotex system is the
18、 hardware and software used to implement a Videotex service. 2.4.2 Videotex terminal The equipment by means of which the user interacts with the Videotex service. A typical Videotex terminal includes: a numeric keypad and/or alphanumeric keyboard and/or other graphical input devices; a visual displa
19、y unit or a suitably modified television receiver; telecommunications network and to generate the display. 1) 2) 3) electronic processing and storage devices required to interface these components to the The terminai may also provide a direct terminal-to-terminal capability, and may include other co
20、mponents, such as a hard copy output unit, magnetic or optical storage devices, and additional processing and/or storage devices. 2.4.3 Videotex user/terminal identification facility A facility which allows the Videotex system to distinguish between authorised and non authorised access to a Videotex
21、 service or certain applications of a service, e.g. messaging, closed user groups and billing, there are three types of identification. a) Identification of the terminal. b) Identification of the user. c) Identification of the line. Recommendation F.300 (03/93) 3 ITU-T RECMN*F.300 (REV* the user, af
22、ter the call with the rerouted application has been cleared, requests access to the rerouting application again. 3.2.2.2.4 Function R4 Request barring of cascade rerouting. Cascade rerouting occurs when rerouted application asks for the call to be transferred to a third application. At the request o
23、f the rerouting application provider, this transfer can be barred by the Videotex service. 3.2.3 Dialogue functions The following functions may be used within the application to retrieve items of information or, to collect data and forward diem to application, according to implementation. 6 Recommen
24、dation F.300 (03/93) ITU-T RECMN*F.300 (REV*L) 93 = 4862593 0582379 TTT = 3.2.3.1 FunctionsDl a) to d) Declare valid an input. The input is forwarded for processing. Several types of input have been identified. In some cases an input is implicitly terminated. a) Free-text input - only limited by the
25、 size of the field. b) Direct selection of a frame if it is directly retrievable. c) Progress through a choice from one frame to another frame by the use of one or two digits. d) Select a frame through the use of a keyword. 3.2.3.2 Function D2 Correcting an input. When the user is inputing data eith
26、er in retrieval or in data collection mode it is the facility to correct an input character by character. 3.2.33 Function D3 Clearing an input. In the same situation as above (D2), it is the facility offered to the user to clear a full input. 3.2.3.4 Function D4 Move one step forward in the applicat
27、ion. 3.2.3.5 Function D5 Move to the next input field. 3.2.3.6 Function D6 Retrace the previous step of the users action. The number of steps may need to be limited and ceriah steps may be excluded from the retrace. 3.2.3.7 Function D7 Move to the previous field. 3.2.38 Function D8 Repeat the frame;
28、 reuansmission of the information necessary to restore the latest displayed image, e.g., in the case of msmission error. Fields will contain the last user input. 3.2.3.9 Function D9 Repeat the updated frame; repeat the same frame with any changes that there may have been since the last access. Field
29、s will contain the default values. 3.2.3.10 Function D10 Return to the first menu in the application. 3.2.3.11 Function D11 Previous menu; retrace the last frame in the previous progression of the users action that allowed a choice in the application. 3.2.3.12 Function D12 Ask for help or guidance w
30、ithout leaving the application. 3.2.3.13 Function D13 Retrace the last frame in the previous progression of the users action that contained a form, without any input by the user. Recommendation F.300 (03/93) 7 ITU-T RECflN*F-300 (REV*3) 73 H 4862573 0582380 733 3.2.3.14 Function D14 Retrace the last
31、 frame in the previous progression of the users action that contained a form, including the contents of the fields entered by the user. 3.2.3.15 Function D15 Interrupt the action in progress. Whether the interrupt results in an abort or a temporary hold is application dependent. 3.2.3.16 Function D1
32、6 Set a marker at the current point in the application for access at a later time within the same session. 3.2.3.17 Function D17 Abstain from forwarding the contents of the input fields. 3.2.3.18 Function D18 Declare valid a set of inputs e.g., the contents of a form are forwarded for processing. 3.
33、3 Present at i on level 3.3.1 General principles 3.3.1.1 enhancements for the presentation level of the international Videotex service. 3.3.1.2 i.e. text consisting of symbols, phrases or sentences in natural or artificial languages, pictures, diagrams and tables. This subclause provides a set of de
34、finitions and specifies a set of functional capabilities and possible The definitions provided, and functional capabilities specified in this subclause apply to text in its broad sense; 3.3.1.3 Each functional capability is individually specified independent of what implementation techniques or codi
35、ng schemes are used by the terminal equipment. Specification of the repertoires and coding is the subject of Recommendations T.lOO and T.lO1. 3.3.2 Structure of display 3.3.2.1 Defined display area The rectangular part of the screen that can be used by the Videotex service. Its structure may be rede
36、fined. (See Figure 1 .) 3.3.2.2 Border area The part of the screen which is outside the defined display area. (See Figure 1 .) TO1 031 5093dOl FIGURE UF.300 8 Recommendation F.300 (03/93) I 3.3.23 Character location structure 1 The defined display area is made up of an array of contiguous character
37、locations in which each character location is the area needed for the display of one character in normal size including any space required to separate alphanumeric characters. In this structure each graphic element is displayed in one or more character locations on the defined display area. 3.3.2.4
38、Cartesian coordinate structure Graphic elements are defined within a two-dimensional space using either normalized or absolute coordinates. Rectangular defined display areas map into the square coordinate space. Normalized coordinates use a Cartesian O to 1 (non inclusive) numbering scheme. As an ex
39、ample, in the case of a television screen with a 4 : 3 aspect ratio, the defined display area corresponds to O to 1 (non inclusive) in the X axis and O to approximately 0.75 in the Y axis. The drawing of graphic elements into the entire normalized coordinate space may he permissible but only the ins
40、cribed 4 : 3 area will be visible. An absolute coordinate system may, for example, use a CCIR-defined siandard for digitized television signals of 540 pixels horizontally and 480 pixels vertically within the defined display area. 3.3.2.5 Active drawing area An active drawing area is an area within t
41、he defined display area within which graphic elements are to be displayed. The definition of an active drawing area cancels any previous active drawing area, but has no effect on graphic elements already Ming displayed. 3.3.2.6 Scrolling area A scrolling area is an area smaller than or equal to the
42、defined display area, within which the characters and associated atmbutes move in specified increments under the action of format effectors (whether explicit or implied) or specific controls. The procedure for scrolling is defined by two processes: 1) the designation of the screen area inside which
43、a scroll operation is to be executed, 2) the execution of the scrolling action. Scrolling occurs in a direction perpendicular to the character path or logical pel path and far enough to bring the next intended character location or the location of the next logical pel just into the scrolling area. 3
44、.3.2.7 Input field This function specifies an input field to be used as a user area on the display screen. An input field may be provided to accept user input fiom the terminal keyboard and to support editing by the user. Any number of input fields may be defined. An input field is preinitialized wi
45、th graphic characters inviting the user to input data. These input request characters may be represented by one or several dots but their display depends on the various implementations depending on a profile of the communication. 3.3.2.8 Marked characters Characters may be marked for further action
46、at the terminal, such as transfer to an output device. More than one type of marking may exist and each may be separately processed. Recommendation F.300 (03/93) 9 3.3.2.9 Protectedlunprotected area Areas within the defined display area can be protected against alteration, manipulation or erasure. T
47、he protection is valid for attributes as well as characters. Protected areas can only be altered by the use of an unprotected function or by the action of clearing the screen. 3.3.2.10 Multi-plane configuration A multi-plane configuration can be defined through multi-plane control commands which inc
48、lude addressing, priority relationship and attribute. For example, a character plane on a photographic plane configuration offers scrolling characters on a steady photographic picture, or a photographic plane on another photographic plane configuration offers simple animation. 3.3.3 Graphic elements
49、 Graphic elements are used to disphy text, including symbols, or pictures. They are categorized below. Applicable to each of the following categories is a set of display attributes and control functions. Attributes and control functions for each category are specified in 3.3.5, 3.3.6, 3.3.7 and 3.3.8, for the international Videotex service. Those attributes and control functions which are commonly applicable to all categories of graphic elements are defined in 3.3.4. 3.3.3.1 Alphanumeric characters 3.3.3.1.1 Alphanumeric characters are those graphic elements pertaining to
