1、INTERNATIONAL TELECOMMUNICATION UNION)45G134 : TELECOMMUNICATIONSTANDARDIZATION SECTOROF ITU-!.G13-!#().%G0G0,!.5!%-!.G13-!#().%G0G0).4%2!#4)/.)45G134G0G0RecommendationG0G0: (Extract from the “LUEG0“OOK)NOTES1 ITU-T Recommendation Z.323 was published in Fascicle X.7 of the Blue Book. This file is an
2、 extract from theBlue Book. While the presentation and layout of the text might be slightly different from the Blue Book version, thecontents of the file are identical to the Blue Book version and copyright conditions remain unchanged (see below).2 In this Recommendation, the expression “Administrat
3、ion” is used for conciseness to indicate both atelecommunication administration and a recognized operating agency. ITU 1988, 1993All rights reserved. No part of this publication may be reproduced or utilized in any form or by any means, electronic ormechanical, including photocopying and microfilm,
4、without permission in writing from the ITU.Fascicle X.7 - Rec. Z.323 1Recommendation Z.323Fascicle X.7 - Rec. Z.323MAN-MACHINE INTERACTION1 IntroductionThis Recommendation describes how interactions should take place between the user and the system from alogical viewpoint. It describes how an effect
5、ive man-machine interface should appear to the user when utilizing thecapabilities of VDTs as described in Recommendation Z.322. This Recommendation supersedes RecommendationsZ.311-Z.317 for interfaces based on VDTs, referencing parts of them where appropriate. Specific human factorguidelines are in
6、cluded within the appropriate divisions of the text.The capabilities of VDTs, e.g., multiple windows, inverse video, etc., when used consistently can lead to amore effective man-machine interface. Additional dialogue procedures are possible and often preferable with VDTs,e.g., using different window
7、s for different applications. Likewise, the transient nature of information presented on ascreen may affect the selection of information display and the manner of presentation. The terminal capabilitiesavailable must be considered in conjunction with guidelines presented in this Recommendation in or
8、der to produce themost effective interface.Many advances in the state of the art of man-machine interface design are incorporated in RecommendationZ.323. However, the use of graphics capabilities have not yet been considered in any detail in these Recommendationsand must be studied further. The need
9、s of the user moving between different systems or different types of terminals arebest facilitated by ensuring that capabilities are used consistently and that user assistance is an integral part of interfacedesign. Interfaces designed according to the principles outlined in this Recommendation will
10、 tend to be more userfriendly, effective interfaces.2 Common aspects2.1 Data displayData display is the presentation of information by the system to the user. During a dialogue the number,dimension and position of windows, window areas and fields in the display area may be changed. Not all fields,wi
11、ndow areas or windows need necessarily display information at any one time.Visual display terminals facilitate information entry through menu selection and form filling. Since presentationof more information at one time might cause confusion, care must be taken to label information clearly, to keepd
12、isplays simple, to highlight information consistently and in moderation, and to maintain a consistent informationlayout as far as possible.2.1.1 General guidelinesThe layout of output is dependent on what type of data is presented. There are three basic types, combinationsof which are possible: text
13、ual data; numeric data; tabular data.a) Guidelines for textual data: text should be written using upper and lower case letters; abbreviations should not be used if confusion might be caused; plain text should be used rather than codes.b) Guidelines for numeric data: strings of more than five numeric
14、 characters may be presented in groups of two to four; standardized formats (e.g., data and time as specified in Recommendation Z.316) should be used.c) Guidelines for tabular data: in case of lengthy columns, spacing between about every five items improves readability;2 Fascicle X.7 - Rec. Z.323 it
15、ems which are related to each other should be placed close together; figures arranged in columns are easier to compare than figures arranged in a row; integers should be right justified; numerical entries with decimals should be justified with respect to a fixed decimal point position; text and labe
16、ls should be left justified; if any text continues on another line, it should begin in the same column as the text above.2.1.2 Accessible and inaccessible parts of the display areaVDTs provide the capability to characterize some fields of the screen as accessible for writing by the systemonly, some
17、other fields accessible for the system and the user.The fields used for the display of headers, parameter identities, delimiters, etc., should be accessible for writingonly by the system (output fields). The fields used for the input of parameters should be accessible both to the systemand to the us
18、er (input fields). The system can highlight these fields, for example, by underlining to distinguish the fieldor a default value, if appropriate. The user can access the field to input the desired value(s), to edit the previous inputvalue(s), or to edit the offered default value.The user may attempt
19、 to write into a field reserved for the system. This should not be allowed, an indicationshould be sent to the user and the input characters should be ignored. The type of this indication depends on theterminal facilities and may be an audible or visible signal. However, the terminal shall immediate
20、ly recover from thissituation so that the user can proceed.2.1.3 HighlightingHighlighting is used to emphasize visually a portion of a display area to make it stand out from adjacentportions, i.e., to call the viewers attention to it. It should be used consistently and in moderation. In particular,
21、careshould be taken not to confuse or otherwise overload the user by highlighting.There are a number of areas where highlighting may be applied, such as: defaults in forms; optional information entry in forms; indication of system irregularities and their urgency, etc.There are a number of possible
22、highlighting techniques, such as: different levels of luminance; colour; flashing; underlining; different character sizes or fonts; small or capital letters (lower or upper case); pointing with arrows, asterisk, etc.; inverse video; combinations of the above.Some guidelines that should be followed i
23、n all applications of highlighting are:a) when colour screens are used: in order to reduce problems for colour-blind users and to facilitate a transition between colour andmonochromatic terminals within the same system, colour should normally be used in combination withsome other means of distinctio
24、n. Note also that some colours may have psychological associations,perhaps depending on the cultural tradition of a nation, e.g., red for danger, green for proceed; be consistent in the use of colour. Colour is a means to recognize rapidly particular windows, windowareas or fields on the screen, ind
25、ependent of any system; colour should be used for additional distinction and emphasis. For example, colour should be used foraiding the user in locating information and for alerting the user to status changes. Colour should be usedsparingly. It should not be used for purely aesthetic and nonfunction
26、al effect as the main aim; if the user is given the capability to modify the colour of any area or object displayed on the screen, theuser should be cautioned about changing colour via any assistance mechanism provided to the user. ForFascicle X.7 - Rec. Z.323 3example, in the case where the user is
27、 changing adjacent areas/objects to the same colour, a warningshould be given. Where the capability is provided, the user should be allowed to make anymodifications desired. Also, it is desirable that secure access to this capability be provided; the number of colours with specific meanings should b
28、e limited. Associating meanings with too manycolours may confuse the user; colour combinations should be chosen such that there is sufficient contrast in hue and density wherevertwo colours meet. This is particularly true in the case where a text is displayed over a colourbackground; colour combinat
29、ions should be chosen with care, as many combinations can be displeasing to the eye;b) use only one level of luminance in addition to the normal level when highlighting. Variations in roomlighting, specific VDTs and user perceptions make it unlikely that more than two levels will be universallydisti
30、nguished;c) when using more than one highlighting technique, do not highlight more than 30% of the display. Ifeverything is highlighted, even differently, then nothing is highlighted;d) since flashing attracts much attention, its use should be restricted to special applications, e.g., alarms. Onceth
31、e user acknowledges the perception of the flashing information, the flashing should be stopped;e) if the user needs to read text from a flashing area, the flashing should be slow in order to make the textreadable. An alternative would be flashing pointers, pointing to the text area of importance;f)
32、in one system, or at least in each job area, highlighting facilities should be consistently applied;g) information can be displayed with underlined characters. However, this type of video attribute might makeit difficult to observe the cursor on terminals where the underline character is used as the
33、 cursor.2.1.4 Information layoutA user should always be able to recognize at first sight: where parameter input is desired in a form; where system response is expected; where the system status is displayed; where user guidance is expected, if requested; where menus are displayed.Therefore, the infor
34、mation layout, when determined by the system, should follow common rules in such a waythat information of certain categories will be displayed in certain portions of the display area.The information layout should be consistent in any one system. Information, which is not necessary in certainjob area
35、s, may be omitted.2.1.5 Description of window areasThe following window areas can be distinguished in a window on the display area: General information window area. This window area can contain system identification and/or applicationidentification, and optionally, date, time, and other relevant inf
36、ormation. This window area is optional; Status window area. This window area should contain alarm indicators of the system being controlled,trouble reporting information from connected equipment, and message waiting indicators. The informationdisplayed may be restricted to the particular application
37、 being controlled. This window area is optional; Work window area. This window area should be used for information entry through form filling and menu-item selection. The work window area may also be used as a graphic display and screen editor area, andshould support scrolling. This window area is r
38、equired for information entry through form filling andmenu-item selection but is optional otherwise; Output and input window areas. These two window areas should support scrolling and should be usercontrollable in size. The input window area should be used for direct information entry. Response to t
39、hedirect information entry as well as output outside dialogue should appear in the output window area. Inputacknowledgements may also appear directly following the command in the input window area. Thescrolling should occur in two window areas separately, or both window areas may be combined into on
40、ewindow area. These window areas are required for direct information entry but are optional otherwise; Special keys and directives information window area. This window area should display function key labelsand specifics about the use of directives. This window area is optional.4 Fascicle X.7 - Rec.
41、 Z.3232.1.6 Ordering of window areasThe relative locations of the status, work, output, and input window areas should be fixed for any given system.Screen layout recommendations for window areas that span the entire width of the window are shown inFigure 1/Z.323. In this case, the screen layout will
42、 have the window areas ordered as shown with the understanding thateach window area remains optional.2.2 Input editingEditing mechanisms can be used to correct erroneous input during data entry or to change previously enteredinput in order to resubmit it.Several possibilities of editing can be disti
43、nguished, including the following: delete last character or last n characters; delete or overwrite last field; delete or overwrite arbitrary fields; insert characters.Editing mechanisms may be dependent on the facilities of a terminal, such as function keys.2.3 Response timeIn a system operating nor
44、mally, response output (see Recommendation Z.317) to a command should bepresented to the user within a psychologically acceptable time limit, normally taken to be of the order of two secondsafter input. For any given type of command, this time limit should be as uniform as possible in order to meet
45、theexpectations of the user.Depending on the nature of the command, two types of response output can be distinguished:a) that which conveys the results of the execution of the command;b) that which concerns the acceptance only of the command, results being communicated to the user by outputoutside d
46、ialogue.Response output concerning user errors should be given to the user as soon as possible. Although a fixed rulecannot be defined, the following guidelines can be given: syntactical errors must be discovered very early by the system; the response time should be within thepsychologically accepta
47、ble time limit; semantic errors can sometimes be discovered early, sometimes late, depending on the type of command andon the nature of the error; normally the feedback should be given to the user as soon as the error isdetected;Fascicle X.7 - Rec. Z.323 5 semantic errors in pre-scheduled jobs shoul
48、d be indicated to the user either immediately after the commandinput, if this is possible, or at the time the result is expected.2.4 DirectivesThe presentation of system output in the form of guidance output, menus, form output, waiting system reports,next page, etc., can be controlled by means of i
49、nput statements called directives. It is possible to qualify the effect ofdirectives either by the use of context or by the use of additional parameters.Directives are used to direct the system to present information rather than to execute a command; they can alsobe used in the interaction between the user and the system prior to command execution.Directives can be given to the system by a word, e.g., HELP, by a special character, e.g., “?” (question mark), adedicated function key, or by non-keyboard devices.Directives can never cause an
