The Design of Interactive Procedures for Man-Machine Communication

Int. J. Man-Machine Studies (1974) 6, 309-334

The Design of Interactive Procedures for Man-Machine Communication T. C. S. KENNEDY

Southend-on-Sea Hospital, Essex, U.K. (Received 10 June 1973) This paper analyses experience in the design of effective interactive communication procedures for computer systems in the light of established research on human verbal skills. The process of normal communication between individuals is examined for principles which may be usefully applied to the design of a manmachine communication language. The stresses imposed by social factors and time/cost constraints are often inadequately comprehended by system designers with the result that systems do not operate as effectively as predicted on technical grounds. Practical experience in the design of data entry procedures is examined and it is suggested that the system, as perceived by the user, should be made very simple and natural in its structure, even though this may involve extensive programming to match efficient internal data structures to the required external model. Finally, a set of ground rules for the design of a "well-behaved" system is proposed.

Introduction The process o f communication between men and machines has undergone detailed study over a n u m b e r o f years with a considerable emphasis on artificial intelligence and the ability o f the machine to realize ~oncepts. The purely practical aspect o f a user communicating with a machine, in order to add to its corpus o f knowledge (entry to a data base) or to obtain advice or information from it, has been relatively neglected with the result that there has been little formal study. Procedures for the interactive entry or access to data bases have largely grown in an unstructured way and it is the purpose o f this paper to attempt to lay down some ground rules for the development o f "well-behaved" systems. The environment o f m a n - m a c h i n e communication to be considered is defined as the "sphere of interaction" and is almost entirely independent o f data base content or design. Within this sphere we are primarily concerned with the ability of the m a n to communicate his needs to the machine in the most concise way consistent with conversational fluency, and with the ability o f the machine to express itself clearly in response. 309

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Man-Man Communication While it is not intended to give a treatise on language in general, it is instructive to examine the ways in which men communicate with each other and to attempt to draw some useful parallels for the development of manmachine communication. The first consideration is the rate at which man-man communicationcan proceed. There are considerable differences between the rate of input and output. Gregory (1969), for example, has shown that the average speaking rate for lecturers is about 125 words per minute (wd/min) whereas an individual reading silently can achieve 250 wd/min with moderately difficult material. This discrepancy is due, in part, to the processing necessary for the formulation of the output (lecture) which occurs in parallel with its delivery. However, there are two other major contributory factors. The first is the degree of hesitation and the use of filled or unfilled pauses which Boomer (1965) has suggested is in order for lexical decisions to be made. The second is the excess of audio and visual cues employed preceeding and during speech which has the effect of cutting the data communication rate drastically. Various attempts have been made to record the upper level or comprehensibility. Foulks (1966), for example, measured intelligibility and comprehension at every rate from 225 to 425 wd/min and showed that comprehension declined more rapidly than intelligibility at higher speeds. He concluded that at higher rates (those over 350 wd/min) the information may be supplied faster than the central nervous system can process it; that is, there may be a physical limit to the rate at which input can be handled. Thus far, only physical redundancy, that is, pauses, introductory phrases and so on, has been considered. A high content redundancy also exists in the syntax of the language and this has a marked effect on the rate of data communication. If this redundancy is reduced or removed, the data rate is improved but at the expense of comprehensibility. At this stage, comprehension of the communication becomes almost entirely context dependent (Bruce, 1956). It is interesting to consider why there is such a high level of redundancy even in purely data communications between individuals a n d why a particular individual fixes the rate at which he communicates. The data rate appears to be at a level below that of the processing capabilities of the central nervous system not only because of the problem of comprehension but also because other, highly organized, assessments are taking place at the same time. This is what could be termed a "social" factor. One individual, talking to another, may be servicing a number of different information channels, for example the inflection of the voice, the timbre or clues to the

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state of mind of the respondent which are not contained in the actual data but are expressed in other terms. It is the capacity to suppress information inessential to the communication which is defined as "concentration" and determines the rate of data transmission for an individual. There is a limited range of transmission speeds over which an individual normally works and this can vary greatly for different individuals. Friedman (1968) measured some of the variations and also showed that comprehension at high speeds was a skill which could be acquired. An example of how this learning occurs naturally can be seen in the different rates which exist between some urban and rural inhabitants. Further, the process of adaptation to the surrounding environment can be observed where there is an interchange of habitat. A limiting stress factor occurs both at the high and the low ends of the range for an individual. At high data rates, fatigue due to heavy concentration causes comprehension to be achieved only for short periods. At the low end, severe stress may be caused by the need for a message to be complete in a reasonable time. One reason for this is that comprehension may be achieved after only a short portion of the message has been transmitted but the receiver has to wait for completion. An example of this is the stress caused to a listener by stuttering, when it appears as if the processor is "hung" until input is complete which can often cause physical discomfort. A less extreme example is the irritation caused when two people, who normally work at different rates, attempt to communicate. Thus it can be concluded that people normally try to operate in a stress-free zone but are capable of working through a limited range. The final point to be considered is the acquisition or creation of language by an individual. McNeil (1966) poses a device called the Language Acquisition Device (LAD) which a child uses to accumulate words and sentences from a set of overheard utterances. The LAD sets up a grammar by processing its input according to rules derived in part from that input. This idea is in conjunction with Chomsky's concept of deeper language structures being formulated from surface structures by a transformation. The transformation is aided by feedback in the form of correction or amplification of the output from the child. Thus the following diagram might describe the process: General utt e r o n c e ~ . , ~ . . _

"'-[--£E5~

Correction or amplification

Fig. 1

sentences i-o

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Mechanization of Communication In order to understand better how men and machines are to communicate it is important to consider the constraints applied by the purely mechanical limitations of input and output devices. Effort is currently being applied to the development of devices, such as speech synthesizers, in order to overcome the mechanical limitations but these have not yet reached the state where they are generally applicable, and we are left with the conventional devices of reading and writing. It is instructive to examine the procedures adopted when men communicate with each other by mechanical devices such as books and papers. If no constraints are imposed, very full communication can be achieved by the use of well-illustrated books. Visual aids such as colour, diagrams, photographs and different printing styles can all be employed in much the same way as hand gestures or variations of tonal quality in speech are used to provide emphasis or maintain interest. However, constraints in the form of production costs necessitate economies which usually result in visual cues being dropped. Colour and photographs disappear and a uniform printing style is adopted. Eventually, even diagrams are lost and the author has to rely entirely on the merits of his style and subject matter to ensure his communication is successful. No time constraint has, so far, been imposed and the situation is very much akin to a batch processing computer system. The author has sufficient time to prepare his material thoroughly, choose his words and order his arguments. As it has been pointed out earlier, the actual input process for the material is far more rapid than a verbal communication would have been but the overall time from inception of the idea is generally much longer. Other examples of this mechanical, batch method of communication are newspapers and letters where, in general, very few limitations are applied to verbosity. However, it is only when a time consideration is important that a further constraint is applied. The telegram is an example where rapid transmission is accomplished but at a high cost. The immediate effect is to reduce redundancy and minimize the number of words or letters actually transmitted. Mandelbrot (1965) has posed the concept of the "cost" of a word in terms of the time taken to transmit it with the assumption that an attempt is made to minimize costs. It is interesting to note that this concept has been applied as a natural development of language. Zipf (1935) has shown that the length of a word in phonemes or syllables is inversely related to its frequency in the printed language and thus a natural economy has arisen. The requirement for economy has led to the development of codes, some

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of which have become a part of everyday language such as £, 7o and so on. With the use of codes and abbreviations, however, context is important once more in establishing meaning. The ultimate extension of this trend is to communicate entirely by a code such as Morse code which was designed such that the most common letters use the shortest sequences. Real-time Commnnication

The effects of real-time communication (other than direct speech communication) via mechanical devices are difficult to determine since it is not frequently a natural occurrence. A simple experiment can be performed where two people are provided with a single pencil and a pad and told that this is the only way in which they must communicate. Even though a highly artificial situation is created, two interesting points emerge; the first is that abbreviations are used as much as possible because of the effort involved in writing messages in long-hand. Second, stress in the form of impatience is built up when a message is partially understood; the receiver rarely waits for a message to be completed. It is reasonable to assume that this stress only occurs in the real-time situation, since if the batch method of communication, by passing notes, is used, little impatience is observed while a note is being written. Fortunately, a more detailed experiment has occurred where the situation is less artificial. At one time a computing system existed where it was frequently necessary for users at different and remote terminals to communicate with each other. Messages were passed from one terminal to another via the central processor of the computer and thus a time constraint was applied by the cost of CPU time. The first noticeable effect was the establishment of conventions for starting, continuing and ending messages. Without conventions, messages could be blocked by a form of "deadly embrace" where both participants tried to send messages simultaneously. It was also important that the conventions established a consistency for the communication method. Those eventually adopted (Facey, 1971) were: (1) Opening a conversation: To let someone know that you want to talk to him, send him a short message such as HI or HELLO. If the response is BUSY, send it again but stop as soon as it is accepted and wait for a reply. (2) Acknowledging a request to talk: If you receive a message, stop what you are doing and acknowledge with a simple reply.

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(3) During a conversation: Keep messages short. Use abbreviations as much as possible. If you need to continue, end a line with -t--~-t-. Never continue unless you have ended a line with -k -k q-. If your message is long, try to split it up so that the other person has a chance to reply. He may have guessed what you are going to say; or he may not want to wait while you type it out. Try and type as quickly as possible. (4) Hang-ups: If you are in control and sending .a message, and the response is BUSY, send it again. Do not wait. The other person should be waiting. If you are receiving messages, do not interrupt until you get a line not terminated by + + + . (5) Closing a conversation: Your last message should end with the word BYE. Having sent this, wait for a response also terminated with BYE. If the reply to the first BYE does not terminate in BYE then the conversation remains open. Two factors influenced the development of the communication language, the first being the time/cost constraint, and the second, the stress induced by receiving a message at a lower data late than could be easily accepted. The fact that a message could consist o f a n u m b e r of lines of text which would be printed with an interval of several seconds between them and that the receiver could not interject until the end of the message, initially caused severe stress on the receiver. Verbosity in messages meant that the concepts might be understood well before the communication was complete. An example is given below of a message passed: T H E SYSTEM NOW HAS A NEW FILE TO H O L D T H E -4--tB O O K I N G LISTS. T H E FILE IS CALLED 'BOO' N, W H E R E N + + IS T H E USER N U M B E R . Note the equivalence to a stutter at the end of lines 1 and 2. When the participants had adapted to the use of the system, abbreviations were used where consistent and contextually correct, and lines became of sufficient length to contain complete concepts so that no carry-over was necessary. The above message would have been transformed into the one below: A NEW SYS FILE EXISTS FOR B O O K I N G LISTS + AN A M E D 'BOO' N - N IS USER N U M B E R

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It was noticeable that over a period a terse and economical communication style was developed which made extended use of abbreviations, but little or no use of codes. The users worked in a relatively stress-free fashion. A further, non-trivial cause of stress in this communication method was the slow printing speed of the Teletype terminals employed, which lag behind a normal reading speed. When 30-character-per-second terminals are used, this form of stress disappears which is consistent with the figures given by Gregory.

Man-Machine Communication The area of man-machine communication to be discussed here is limited to the development of an interactive communication language and data collection procedures. The type of system considered is similar to that described by Yntema (1961) where the machine assembles and presents to man the main facts he will probably need to make a decision. H e m a y call for additional information and will indicate to the computer the action which he has decided to perform. The machine may make decisions by simple rules and require man to monitor and modify these decisions as necessary. It is in the communication with the machine at this level that the relevance of the previous discussion to the design of a system becomes apparent. Martin (1973) has tried to distinguish two classes of man-machine interaction which he postulates have arisen because of differing needs. In the first class, the user is entirely familiar with the system and operates it all day and every day; there is pressure put on the user by the need for a rapid response, and there are technical constraints because of the computer hardware. From this has developed the almost exclusive use of mnemonics, abbreviations and codes. An example is the process of communication by means of a mnemonic language (Morris, 1967) where typical mnemonics used are: SSO--set following switches to off. VEL--verify event lamp lighted. Fixed format entries are used and a typical command might be as below: SSO$12355245POWER ONSON, where the $ signs are essential separators. The use of such a system requires a trained operator who can carry the entire dictionary in his head to code effectively, and who can remember the format he is to use. The most prominent feature of this approach is its rigidity. Little attempt is made to give guidance to the user in the event of an error or to allow the correction of an error other than by re-entering the command string. The rationale behind the design is that the operator is so familiar with the system that he can memorize

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all the codes and mnemonics; the transmission of data between a terminal and the computer is reduced to a minimum; and the speed of response is high because the operator uses short messages and there is little difficulty for the computer in analysing them. The second class is that of the casual user who interacts with the system only rarely and who therefore requires a great deal of help in performing the action he intends. A typical method used is to present the operator with a number of alternative actions from which he may select one by a simple response. A further set of choices or requests for data is then presented and so on until the objective is reached. The operator is told exactly what to do at each step and his response is always short.With this system a relatively large quantity of data has to be transmitted by the computer which is time consuming and may be expensive in terms of transmission and storage costs. Neither of the systems mentioned above have tried to use the power of the computer to help the interactive process to a degree where a dialogue or conversation could be said to be taking place. An attempt to solve the problem of making the computer more readily accessible to other than the most sophisticated users, has been made by a combination of behavioural scientists and systems software designers. Powerful influences have come from the computer-aided instruction (CAI) field where use is made of information structures of facts concepts and procedures to generate text and questions. The possibilities of developing mixed-initiative dialogue have been demonstrated quite clearly (Carboneil, 1970). Another influence has been the systems software generated for simplifying the task of program writing; of particular interest have been the interactive text editors and program debugging packages. With these programs the user has been given a command structure, consisting of a number of mnemonic commands, to process computer files. The design and development of interactive command languages and data entry procedures is the subject of the remainder of this paper.

CommandLanguages The structure and design of command languages cannot be generalized and is usually specific to an application. However, it is possible to establish a useful set of conventions and ground rules which may be applied almost universally. It is necessary at the outset to realize that a good command language will probably require complex programming. One of the main factors contributing to the neglect of the art has been a reluctance to accept this overhead as an essential part of any system.

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It is important in the design of a command language that a convention is established for communication between the user and a program. The adoption of "cues" is common, so that the program instructs the user and gives a positive indication of the response expected. These cues are similar in effect to the social content of human intercourse in that the respondent learns to recognize the program he is "talking to". Further, the cues serve as a rejoinder; the equivalent of a nod, eye movement, noise or gesture to show that the computer is taking note of what is being said. This is very important with a naive user in establishing a feeling that a positive interaction is taking place and giving the security that a response has been successful. Cues also serve to distinguish different parts of complex systems so that a command chain does not become a maze. The use of codes, purely mnemonic commands and fixed formats should be avoided. However, attempts at entirely natural language communication have been largely fruitless and in some cases quite harmful. One natural language system DEACON(Craig, Berenzer, Corney & Longyear, 1966), can analyse quite complex input but has quite serious limitations. The processing time for analysis is long, there is a limited dialogue only, ambiguities cannot always be resolved and could lead to false information being provided, a large storage is required and the operator's response is long-winded. Martin (1973) also argues that an untrained operator can be misled by such a system into supposing that the computer understands more than it really does, which leads to errors. An example of the sort of sentence that DEACONmight analyse is: PLEASE LIST ALL T H E BOOKINGS FOR M R J O H N SMITH. However, it is arguable that even a naive operator would wish to communicate his request to the computer in such a formal and verbose form. A terse and economical style which would transform this request into the one below is at least as effective. LIST BOOKINGS SMITH This style, in which the command verb predominates, lends itself to easy analysis and manipulation. The predicate is optional and the computer will only obey the command when it has sufficient unambiguous information on which to act. If it requires more information it will request it. Thus in a typical system the interaction could be as above or as:

LIST W H I C H LIST : BOOKINGS W H O FOR : S M I T H (Note: response from the user is underlined.)

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Wherever it is possible, the command verb should describe exactly the function which is to be performed, thus, P R I N T might mean print a line or a record, and LIST might mean list the contents of a file. However, it is equally important that the user who is familiar with the system is not required to give long-winded commands, and thus the program should be able to distinguish any unambiguous abbreviation of a command, such as PR or L. This approach is derived directly from systems software design of interactive computing languages (Facey, 1973) where a simple and economical entry of program statements is required which yet allows program listings of absolute clarity. An example of the entry of a program might be: 10LX = 1 15PX~rX:LX--X+I 20 LI

:UX>4:

When listed this program would look like: 10 LET X = 1 15 PRINT X.k X : LET X -----X + I : UNLESS X > 4 : LOOP 20 LIST Note that in line 20, ambiguity is resolved by entering LI for LIST which can be distinguished from L for LET. This facility for interpreting a command from a minimal input is necessary if a range of users is to be accommodated. The naive user has a set of meaningful commands which can clearly express the action to be performed, the sophisticated user has a rapid means of communication. An interactive system should be capable of perceiving where help is required by the user because he has not understood a command or has forgotten the range of commands available to him. At any stage in a sequence of actions, the user should have the facility to ask what is expected of him if he is in doubt. As an example, consider part of a data entry sequence: S U R N A M E : JONES INITIALS : A.J. TITLE : ? M R MRS OR MISS TITLE: The user responded with a question mark when he did not know how to respond, and the possible responses were printed. The use of a manual in this context is not nearly as effective as a message from the computer since it

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causes a disruption of the interactive process. Maintenance of conversational fluency plays a large part in making it possible for a user to learn rapidly how to use the system. It is the equivalent situation to a student trying to learn either from a book or a teacher. A H E L P key or command, which gives a detailed description of a selected part of the system is essential if only to give confidence to a casual or naive user. It is often difficult, initially, to persuade someone to use a terminal when they are unsupervised since they have no means of asking questions. If the user can ask the computer what to do at any stage or to explain how a particular function works, the process of familiarization proceeds fairly rapidly. A parallel can be drawn with a diffident person attempting to start a conversation with a stranger. If the stranger is silent, proceedings will be slow. If, however, there is a warm reaction, rapport will be established quickly. Interaction with such a "guided" or self-teaching system has been shown to be the quickest and surest way of teaching the use of terminal systems (Kennedy and Edmunds, 1974). When errors are detected, every attempt should be made to pin-point them accurately, to give the exact cause of error and to describe the appropriate corrective action which should be taken. Here is an example: L I S T PLANTINGS S M I T H T H E R E IS NO LIST C A L L E D P L A N T I N G S T R Y BOOKINGS OR ADMISSIONS However, verbose error messages should be avoided for the sophisticated user who has simply made a typing error. An example of bad design is a system which, when it cannot interpret a command, automatically gives a list of all the available commands. A more satisfactory approach is to print a short message showing that the command has not been understood and advising the user how to obtain a list of the commands, for example PLANT ? TYPE * FOR A LIST OF COMMANDS. The experienced user should have a facility for suppressing long error messages. The main criterion is to adjust the flow of the interaction to the ability of the respondent. Nothing upsets a fluent speaker more than to be continually interrupted with long comments, whereas a hesitant speaker may be grateful for help. Thus, in analysing the response to a cue, the computer has to be able to separate an approximately correct reply from rubbish. A typical system (called PBS) using such a command structure for primarily naive users in a medical environment is described at (Kennedy & Facey, 1973).

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Within the command language there may be many substructures and it is here that the relevance of the proceeding discussion is most apparent.

Structures With relatively simple systems, the structure of the command language is usually linear, that is all the commands operate at the same level, and completion of any command always returns the user to the command level. A command may initiate a sequence of actions which can be either completed or aborted; no branching is permitted. An example of a substructure in a linear system is the C H A N G E command in PBS which was designed to allow a user to alter any part of a record stored in a file (the cue, PBS, in the example below is the main cue indicating that a command is expected). PBS: CHANGE 6 ITEM: BIRTH DATE B I R T H D A T E : 1/3/42 : 4/6/64 Note that the cues used through the process are quite different from the main cue and follow a logical, conversational sequence before returning to the command state. This system has the advantage of being easy to use and totally consistent. For any command, only one possible action or sequence of actions can be taken. As more complex systems are approached, it becomes immediately apparent that a linear structure is no longer satisfactory. There are two main problems. First, the command imperatives, such as LIST, may describe two or more different operations, and it is not always easy to find alternatives which have equal clarity. In one instance at least, a frantic search through Roget's Thesaurus has been resorted to in order to resolve ambiguities. As the vocabulary of the command language is increased it becomes more difficult to use simple and obvious words to express a requirement. The second problem is that as a system becomes more complex some commands require more arguments in order to fully define their actions. As an example, consider a simple system for managing hospital waiting lists (Kennedy, 1973; Kennedy, 1974). Initially, when only one waiting list is being handled, the command LIST is adequate to cause the list to be printed. However, as more lists are added, it is necessary to state whose list should be printed. It might also be required to specify which hospital the list is for. These additions all contribute to increasing the verbosity of the language since the arguments are necessary each time a command is given.

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The solution to these problems seems to lie in a slight relaxation in the consistency of action taken by the computer and in the use of dosed subsystems with one or more levels at which commands may be interpreted. The only loss of consistency which should be permitted is that some commands may become context-dependent, that is their action may differ in different circumstances. Consider the example of a hospital administration system which is composed of waiting-list administration, booking and admission scheduling, in-patient administration and so on. It is apparent that to add a patient to a waiting list it is necessary to specify each time which list is being used. It becomes much simpler if a closed waiting list system is used such that all operations are performed on a specified list. The use of such a system means that within a subsystem a command such as P R I N T has the meaning "print a waiting list record" whereas outside the system it has a meaning "print a record". This loss of consistency is likely to cause difficulty only if the results are not logical. An interesting point with such a structured system is that it becomes necessary for structures to be able to communicate with each other. For example, consider the system of Fig. 2. Level 1 (main command level)

Wait

Level 2

Waiting list system List Print Change

List

Print

Change

I

Book

Postpone

Admit . . .

I Patient booking system List Print Change

Book ~ Postpone

• Postpone

Fig. 2

All commands are interpreted at level 1 and the specific action is performed. Some commands are also interpreted at level 2, with the same meaning but possibly a slightly different action. It is often the case that a user in the waiting-list system (WLS) will wish to use facilities in the patient

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booking system (PBS) without recourse to the main command level. It is here that the techniques of systems software can be applied with great effect. If cross-linkages like this are to be used, it is necessary to have a run-time structure to the system which represents what the program is doing at any time and which is accessible to the program. An example of such a function, adapted from Stansfield (1972) and applied to the above system is: " I f I'm in the waiting-list system and I have booked someone then close the booking list and re-open the waiting list, otherwise return to the PBS command stage." This digression illustrates the structure necessary to maintain a simple command language and logical consistency in the control of a complex system.

Timing Martin has, quite rightly, placed some emphasis on the importance of a careful balance of timing in the interaction between a user and the computer. This has been discussed earlier when stress and the rate of communication were considered. In the design of computer systems, especially those involving sharing the use of central processor time, it is difficult to accurately estimate delays involved in processing. Often it is a function of the mix of programs being run by other users which is the determining factor. However, it is possible to design round this problem and make sure that the majority of delays only occur when they are acceptable. Conversational fluency requires a fast response by the computer to any input from the user. Martin uses the concept proposed by Miller of "task closure" as the break-point after which delays can be acceptable. As an example, if data is being entered from a document into the computer by a question and answer sequence (see below), there should be a rapid response to each entry in order that conversation is simulated. A response within 2 sec is proposed as being acceptable. At the end of a sequence however, the task is completed and a delay is satisfactory or even desired in order to savour the satisfaction derived from task closure.

Data Entry Data entry to computer files is one of the more common activities associated with computers and can involve a range of users from the naive to the sophisticate. Many systems have been evolved to cater for one or the other, but it is rare to find a completely satisfactory design for both. The main criteria applied are usually those of accuracy and speed with little attention being given to the stresses involved. It is of interest to examine one of the common methods in use with visual

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display terminals which simulates the manual entry of data to a form. A fixed format display is presented on a screen, with gaps left for the entry of data. The display may contain such cues as "name, address" and so on and probably will match fairly closely the form from which the data is being entered. Each entry is displayed in the appropriate place on the screen and verification by the user is quite simple. Often, extensive editing is possible by deleting characters or complete entries and sometimes back-tracking is permitted. The drawbacks of such a system arise in those areas where it has departed from the principles outlined previously. Little interaction between the program and the user is possible and there is no conversational mode of operation. If errors are detected on input, the screen must be cleared for presentation of an error message which means that the user cannot compare his entry with the error. This is disorientating which, in turn, induces stress. Since entry is being made from a document on to a display screen, already containing some information, it is not easy for a user to keep track of his position on the "form". The device is often employed of flashing a cursor or the next cue to show where the next entry is expected. Impatience can be attributed to the computer and the rate of interaction is removed from the "social" level to a "mechanistic" level under control of the machine. A detailed example is given in Appendix I of a simple data entry procedure used to collect information for a hospital waiting-list. The system is designed to be adaptive and has employed many of the principles discussed previously. The procedure is part of a waiting-list system implemented on a time-sharing bureau computer. Essential to the implementation has been the availability of a high-level language with powerful string and file handling capabilities. The language used, QUASIC (Gaines, 1970; Facey, 1972), is a much extended and modified version of Dartmouth College BAsic. A question-and-answer sequence is used in order to collect data. Each question is presented in the form of a cue, prompting the user for the next response. No excessive sense of urgency is imparted by this process and the rate of entry is controlled entirely by the user. The cues can be adjusted by the user to suit his familiarity with the system or they can automatically adapt as his experience grows. Initially the cues may be very explicit and then adapt to be suitably terse to reduce redundancy and speed up the interaction. Similarly the response by a user may be abbreviated in most cases. Thus the state may be reached where a user and the machine are interacting in a language of abbreviations where context has a high value in establishing meaning. As an aid to this process, the detection of an error results in a more explicit version of the cue being presented to reduce the level of abbreviation until a correct entry is made.

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Wherever possible, help is given to the user to show him the type of entry which is expected. For example, the "date of birth" entry has to be in the form "day/month/year" in order for the computer to interpret it. When an entry is made, it is analysed in detail and if an error is detected an appropriate message is printed to show the user which part of his entry is incorrect. Each entry is checked to ensure that it conforms to what is expected at any point. A free input format is allowed where possible; fixed formats are only required to remove ambiguities in input. No codes are employed in the input procedure since this would require the user to memorize or have a reminder of their meanings. Where a code is to be stored in the computer file, it is generated by the machine. For example the title of the patient is actually stored as a number 1, 2 or 3 derived from the position of the title in the list MR, MRS, MISS. Thus MRS is interpreted by the computer as internal code 2 and is stored as such. As a consequence, the machine is being used to interact with a user in a fairly natural language form to collect data which is compressed for internal storage, The necessary interface between the user and the data file, the sphere of interaction, is complex. Detailed examples have been given in Appendix II of the manner in which entries are analysed in order to perform the sophisticated interpretation required. The system attempts to work on a social level of communication in that a proportion of the interactive procedures approximate to natural conversation. As an example, error messages are meaningful, polite, and suggest an appropriate course of action to remedy a fault. On the other hand, every attempt is made to ensure that a user works in a stress-free environment by adapting the conversation to be sufficiently terse to suit his level of understanding. If the social content of the communication is to be maintained, it is essential that the computer is not seen to assume control of the system (except where it is expedient in order to complete critical file processes) and there should be no action taken by the computer which cannot be terminated if required. An important example of where the user should retain control occurs in the question and answer sequence of data entry. There should not be the feeling that the response to a question is final and immutable. The user must be able to change his mind about any response he has made. To do this, a record-editing facility, after a record has been completed, is usually insufficient since it destroys the idea of a conversation taking place. It is preferable that the user should be able to retrace his steps through the sequence to correct a previous entry. The final point to be considered in maintaining a stress-free environment, for interaction is that of consistency of action on behalf of the computer.

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It is important that if the computer performs a particular action on receiving a response from the user then that action is always taken for that response. This is often not fully appreciated by designers without experience of systems design for naive users. A typical problem is the "default option" which is used to allow someone who is familiar with a machine to initiate action with the minimum of effort. A program to produce paginated listings of any source text, for example, has a command string: OPTION ~- F I L E N A M E where the options may be: P

list on paper tape; default: list on Teletype.

D

delete comments; default: leave comments.

S

selective listing using current paging; default: list all.

The default options are designed to be those most commonly used and thus, most often the command string will simply be: <-- F I L E N A M E with all default options assumed. When this technique is applied to a question and answer sequence the problem of maintaining consistency becomes acute. For example, a null response might be used as the default option to indicate the most common response to a question. Thus from question to question the meaning of the default is changing. It is possible to get round this problem by carefully matching the defaults to the document from which data is being entered such that positive responses are only required, where indicated. Appendix 1 is an example of a system which has attempted to follow logically consistent lines.

Conclusion An attempt has been made to describe the process of evolution of a language of communication between a range of users from the naive to the sophisticated and a computer system. A set of ground rules for the design of a "well-behaved" system has been proposed. The rules are summarized below: (1) Communication should be carried out in a terse "natural" language, avoiding the use of codes and mnemonics. Abbreviations should be allowed wherever possible. (2) Each entry should be short so that errors can be corrected simply and a reasonable tempo can be established.

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(3) Where arguments are necessary for an entry, the user should be able to enter these individually or in a string, depending on his level of ability. (4) A social element to the communication should be maintained to make full use of the speed and accuracy which can be achieved in a conversational, interactive ambience. (5) The user should be able to control the length of cues or error messages to suit his facility with the system. (6) Error messages should be polite, meaningful and informative. (7) The computer system should give help when requested or whenever it perceives that the user is in difficulty. Self-teaching is recommended. (8) The command language should be simple and the behaviour of the computer should appear to be logically consistent under all circumstances. (9) Control over all aspects of the system must appear to belong to the user. (10) Redundancy in the dialogue should be avoided or reduced, especially as the user becomes more familiar with the system. (l l) The system should adapt to the ability of the user. (12) The rate of exchange must be within the user's stress-free working range. Control of the rate should always appear to belong to the user. The growth of confidence by the user will enable a language to be developed on similar lines to the Language Acquisition Device proposed by McNeil (1966). It is not within the scope of this paper to expand that theme, however, its relevance to the development of an adaptive communication system should be apparent.

Appendix 1 A DATA ENTRY PROCEDURE

The data entry procedure described below has been implemented for use as part of a hospital waitingqist system. The data is collected at a clinic on a card, the "to come in" (TCI) card an example of which is reproduced at Fig. 3.

-v~SS E L "~MRS. mr~K~/ SURNAME (block letters)

TCI

~

UNIT No. ~ B ~OFD IRTH A T

FIRST NAMES

UNDERTHE CARE OF

~'1~~ .

~2I~. ~ . L TELEPHONE

PRIORITY ring~t~riate number (w DIAGNOSIS

ADMIT ON 2 (within 12wks)

ks)

3 (within 26 wks) CODE

SH~NOTICE

SOCIAL CARE~ YES CATEGORY X-RAY " F A K E ~ STAFF P.P. AMENITY. YES PRE-OPERATIVETREATMENT

THEATRE(rains) STAYT~JE~(days) " ~ ~) I NO ADMISSION BE E & PRE-OPSTAY (days)

NO

L.M.P.

MENSTRUAL CYCLE

SIGNATURE

DURATION

UNDER PUBERTY BEYOND MENOPAUSE

~l ~ ~

DATE

Fig. 3

Data is entered to the computer in the following sequence using the TCI card as the data entry form. Note the close correspondence between the layout of the card and the entry sequence.

(1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) (12) (13) (14) (15) (16) (17) (18)

Typical abbreviation

Entry

Full cue

Type of entry

TITLE SURNAME INITIALS U N I T NUMBER DATE OF BIRTH PRIORITY DIAGNOSIS OR TREATMENT CODE SHORT NOTICE SOCIAL CARE THEATRE TIME ESTIMATED L E N G T H OF STAY CATEGORY OF PATIENT X-RAY TAKEN ADMISSION CONSTRAINTS PRE-OPERATIVE TREATMENT GYNAECOLOGY CALLER

TITLE SURNAME INITIALS UNIT NUMBER BIRTH DATE PRIORITY

T1 SURN INIT UNIT BIRTH PR1

A A A A BC A

DIAGNOSIS CODE NOTICE CARE THEATRE

DIAG CODE NOTI CARE THE

B B D D B

STAY

STAY

B

CATEGORY XRAY

CAT XR

D D

CONSTRAINTS

CONS

DC

PRETREATMENT

PRET

DC

CALLER

CALL

D

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T. C . S . KENNEDY

Entry types have the following meanings attached to them: A, Compulsory. If the response is null the cue is printed again in full.

B, Entry is not compulsory. A null response is accepted and means unknown. C, Entry is conditional. A null response is accepted and means "not relevant"; the next (subsidiary) cue is skipped. D, A null entry means "no", "not true" or "use default option". Some items in the above list need explanation. The first four items form the patient identifier and an entry is therefore compulsory. The patient's age is calculated from the date of birth. If it is possible to directly classify the patient into an adult or a child, from the age, this is done. If the classification is not possible because the age falls into an indeterminate range (11-15 years) the subsidiary cue, CHILD ?, is given expecting a yes/no response. The code, item 8, is any code or set of codes which a consultant may have defined for his personal use, such as an asterisk, to bring a particular point to his attention. The category, item 13, is whether the patient is a member of staff, an amenity or private patient. Item 15 has a subsidiary cue, DATES, which expects the response of the date or dates between which admission could not be accepted. Items 16 has a subsidiary cue, PRE-STAY, which is the length of stay required before an operation, because of pre-operative treatment. Item 17 is an alternative to item 16 and applies only to day-stay gynaecology patients. The cues presented are governed by a mask which is set to the requirements of a particular consultant. Thus questions on gynaecology patients are only asked for the gynaecology consultant. The subsidiary cues are only presented if the answer to the main cue requires it. In this way the basic sequence is adapted to the responses. Local editing allows the user to perform the following functions: (1) Rub out any character or any number of characters input. (2) Delete an entire line input. (3) Terminate the whole entry procedure and delete the partial record input. (4) Return to the previous cue to allow a correction. The input procedure may be backspaced in its entirety. Some standard inputs, such as category of patient, can be abbreviated; for example, AMENITY could simply be entered as A.

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There are numerous events which may occur on input, since the process is intended to be self-teaching to some extent. Each cue is described below with examples of the action.

Title The normal response is one of MR, MRS or MISS. The sex of the patient is derived from the response. A null entry causes the cue to be printed again, an invalid entry causes a print-out of the valid entries. More than two bad attempts causes a suggestion to be printed that the user should type H E L P to get instruction on the command. Surname An entry is accepted up to a preset maximum number of characters. A null entry causes the cue to be printed again. Initials Any entry is accepted, as described in Appendix 2. A null entry causes the cue to be printed again. Unit number Any entry is allowed (unit numbers are the numbers which identify the patient's case notes. The numbers may be up to six digits long and no attempt has been made in this implementation to check for validity). Entry is compulsory so that if there is no trace of the case notes or if the unit number is not known, a message to that effect should be entered. Date of birth The date of birth is expected in the tbrmat day/month/year. I f any other format is attempted an error message indicates to the user the correct entry. Each part of the input is checked for validity, i.e. more than the correct number of days in a month or months in a year. The date cannot be in the future nor will patients over 120 years of age be accepted. Each error encountered is interpreted specifically and an appropriate error message is printed. A null response shows that the date is not known and is accepted. The age is calculated from the entry and if it is less than I 1 the patient is classified as a child; if it is greater than 15 the patient is classified as an adult. Between these two ages the classification is uncertain and the subsidiary cue C H I L D ? is presented, expecting a yes/no answer. In the case of an unknown date of birth entry, the subsidiary cue is also presented.

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The "child" cue is of type D, that is, the response may be "yes" or " n o " or null. The null response meaning the default option "no".

Priority The normal response is 1, 2 or 3. A null entry causes the cue to be printed again, an invalid entry causes a print-out of the valid entries. Diagnosis Any entry, up to a preset maximum number of characters is allowed. A null entry means not known. The diagnosis which is entered is interpreted if possible by comparison with a prestored list for that consultant. If an interpretation is achieved a code key is stored for a later search. Code A pre-defined set of codes is stored on the waiting list for a consultant. The entry is checked against that list and if a match is found it is stored. If no match is found the list of possible entries is printed. If the code is re-entered it is accepted and added to the list. A preset maximum number of codes can be accepted and an error message indicates if this is about to be exceeded. A null entry means not known. Short notice Response should be yes or no. A null response takes the default " n o " . Social care As above. Theatre time The theatre time is entered in minutes and interpreted as a value to the nearest 15 rain. A null entry means not known. An invalid, i.e. non-numeric entry causes a print-out suggesting the format of a correct entry. Stay The expected response is either DAY or a number of days' stay. A null entry means not known. An invalid entry is treated as above. Category The expected response is one of the four categories NHS, AMENITY, PRIVATE PATIENTS or STAFF. An invalid entry causes a print-out of the valid entries. A null entry assumes the most common entry, NHS, as a default.

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X-ray As for short notice. Admission constraints The normal response is "yes" or "no". A null response means "no". If the response is "yes", the subsidiary cue of DATES is presented to elicit a date one or two dates between which the offer of admission to hospital cannot be accepted. The entry is similar to that for date of birth except that if two dates are to be input, there must be some separator, usually a comma, between the two dates. Pre-operative treatment The normal entry is "yes" or "no". A null entry means "no". If the response is yes, the subsidiary cue, PRESTAY, is presented to find the number of days of preoperative stay required. The response to this cue is exactly the same as that to the STAY cue above. Caller The normal response is the initials of the consultant or registrar who signed the TCI card. A predefined set of people who are allowed to add patients to the waiting-list of this consultant is stored with the list. The entry is checked against this set and if a match occurs a code is stored. If no match occurs the procedure is the same as that for the CODE entry. A null response means, take the most common entry which is the consultant himself. The above description should indicate that the system is aimed at a range of users with a fairly broad experience. The naive user gets as much help as he requires to complete an entry successfully, the sophisticated user can achieve a rapid, terse interaction with the system. Each user works at his own pace. The design has attempted to be logically consistent to avoid confusion. Attempts have been made to make the system adaptive and selective in its presentation of questions.

Appendix 2 E X A M P L E S OF S T R I N G ANALYSIS

One of the most powerful features of the QUASIC language is its ability to manipulate strings by use of a new command, PUT. The command is described as follows (Facey, 1972): P U T SE [OP $ M A T C H SE'], where SE and SE' are string expressions, OP is an operator, $ is a string variable, M A T C H is a simple string (literal string or string variable) or a

332

T.c.s.

KENNEDY

variable for assignment. The fields within square brackets may be iterated, and the fields themselves are to a large extent optional. The P U T statement has the effect of taking the string SE and splitting it up according to the operator and match; the part of the string before the match going into the variable $, followed by the replacement string SE'. The possible operators are: >, Close any destination strings previously opened and open a new destination string specified by the $. Any matches to be embedded ----, Any matches to be anchored <, Leave destination string open. Any matches to be embedded. > , Temporarily close the output string until next operator is encountered. Any matches to be embedded. The match can take the form &G NE, where N E is a numerical expression, which when evaluated means get the next N E characters passed over in an embedded match and assign them to $. As an example consider the analysis of an input in response to the cue "initials", A free-form input has been allowed, but the output is always required in the form "A. B. C.". Thus all inputs such as: ABC A B C A.B.C. A..B C., and so on are accepted and converted to the required output. The program reads: 160PUTS> $ .... < :LOOP 165 P U T $ > S ' . . ' ' '< :LOOP 170 P U T > $ 2 : I F S < ' . ' : G O T O 1 8 5 175 P U T S > $ 1 & G 1 > $ : P U T $ 2 $ 1 ' ' ~ $ S : LOOP 180PUT$2>$ 185 continue. There are two things to note for those not familiar with extended BASIC. The first is that several commands may be contained on a line if they are separated by a ' : '. Secondly. the PUT command has an implied branch in that if it can be successfully completed, any further commands on the line are executed; if it fails however, the rest of the line is ignored and the next line is executed. It is assumed that the input in response to the "initials" cue is contained in a string variable $. Line 160 then puts any characters in $ into a destination string $ until the character "space" if found (match with literal string ' ') which it replaces with the character "stop" (literal

MAN-MACHINE COMMUNICATION

333

string expression ' . '). If such an action is successful the destination string is left open and the LOOP command executed so that line 160 is performed again. This is repeated until the PUT command is unsuccessful when line 165 will be executed. Thus if $ contained the string A B C at the start of line 160, when the PUT command failed, $ would contain A.B.C. If $ contained the string A.B C initially; after execution of line 160 it would contain A..B.C Line I65 would then convert this to A.B.C by a similar process. Line 170 first places a null string in variable $2 and then checks whether $ contains a ' . '. If it does, the process is complete; if it does not then the input was of the form ABC. Line 175 strips off the first character of the input string and puts it in $1 and the rest of the string into $. Then $2 is concatenated with $1 and the literal string ' ' and put into $2. The first time line 175 was executed $2 would contain 'A.' and $ would contain BC. The line is repeated until finally 'A.B.C.' is in $2. Line 180 puts $2 into $ so that the continuation at 185 is the same as if the branch was from line 170. It will be noted that this example is not exhaustive, it is intended rather to illustrate the procedures. A second example is of the process of checking an input against a predefined list and if a match is found storing a code as a result. The responses allowed to the cue "category of patient" are NHS, PP, AMENITY or STAFF. A very simple method of checking a response would be: 200 P U T ' , ' $ > S : IF $ 4 0 < $ : L E T C A = Q I : G O T O 2 1 0 205 PUT $40 = ' , ' > $ : PRINT 'ONE OF '$ : GOTO input process 210 continue where $40 contained the possible responses separated by commas, and the input is contained in $. Line 200 concatenates the literal string ' , ' with the input and puts it into $. Then an embedded match search is made of $40 to see if it contains the input. The system variable QI is incremented each time the first character of $ (i.e. ' , ') is encountered in $40 up to the point where a total match, if any, is found. Thus if the input had been AMENITY, CA would be set to 3 and stored as such in the record. A simple error message can be printed by line 205 if the input does not correspond with any of the possibilities in $40. It should be clear that an abbreviated input will be satisfactory and will be matched. There are obvious extensions to this process such as applying partial matches in order to be more selective in the error messages. The allowed inputs in $40 could be adapted to contain some new inputs when the system is in operation so that the allowed inputs are interpreted in the forms most commonly used.

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References BOOMER,D. S. (1965). Hesitation and grammatical encoding. IEEE Trans. Language and Speech, 8, 132. BRUCE, D. J. (1956). Effects of context upon the intelligibility of heard speech. Third London Symposium on Information Theory. Ed. C. Cherry. CARBON'ELL,J. R. (1970). An A.I. approach to C.A.I. IEEE Trans. Man-Machine Systems MMS-11, 190. CRAIG, J. A., BEREZNER, S. C., CORNEY, H. C. & LONGYEAR, C. R. (1966). DEACON: Directed English Access and Control AFIPS Fall Joint Computer Conference, 29, 365. FACEY, P. V. (1971). Internal memorandum, Essex University. FACEY, P. V. (1972). B A S Y S User's Manual. Dept. of Electrical Engineering Science, Essex University. FACEY, P. V. (1973). QUASAC User's Manual. Dept. of Electrical Engineering Science, Essex University. FOULKE, E. & STICHT, T. G. (1966). The intelligibility of time-compressed speech. Proceedings of the Louisville Conference on Time Compressed Speech. FPaEDMAN, H. L. & JOHNSON, R. L. (1968). Compressed Speech. Correlates of listening ability. IEEE J. Communication, 18, 426. GA_rN~S,B. R. (1970). QUASIC User's Manual Questel Ltd., London. GREGORY, D. S. (1969). Compressed speech--the state of the art. IEEE Trans. Engineering Writing and Speech, EWS-12, 12. KENNEDY, T. C. S. & FACEY, P. V. (1973). Experience with a mini-computer based hospital administration system. Internatl. J. Man-Machine Studies, 5, 237. KENNEDY, T. C. S. (1973). A waiting list system. Management Services Division, North East Metropolitan Regional Hospital Board. Report No. 376. KENNEDY, T. C. S. (1974). A computer-based waiting list system. Medical Data Processing Symposium, March. Institut de Recherche d'Informatique et d'Automatique, Toulouse. KENNEl)Y, T. C. S. & EDMUNDS, R. (1974). An examination of Training Problems with Naive Computer Users, May. European Computing Congress. Brunel University. MANDELBROT, B. (1965). Information Theory and Psycholinguistics. Scientific Psychology. Eds B. B. Wolman and E. Nagel. Basic Books. MARTIN, J. (1973). Design of Man-Computer Dialogues. New Jersey: Prentice-Hall. McNeIL, D. (1966). Creation of language. Discovery, 27, 34. MORRIS, J. E. (1967). Construction of a mnemonic dictionary for computer-aided engineering writing. IEEE Trans. Engineering Writing and Speech, EWS-10, 41. STANSFIELD,J. L. (1972). PROCESS 1 : A Generalization of Recursive Programming Languages. Bionics Research Reports, No. 8. School of Artificial Intelligence, University of Edinburgh. YNTEMA, D. B. & TORGERSON, W. S. (1961). Man-computer co-operation in decisions requiring common-sense. IRE Trans. Human Factors in Engineering, HFE-2, 20. ZIPF, G. K. (1935). The Psycho-Biology of Language. New York: Houghton Mifflin.