In the beginning, there were three JAs:
• Interleaving, for whatever reason, within a number of constraints. • The person should have some experience with the individual tasks.
• A certain degree of unpredictability, so for example the possibility of interruption. The previous chapter ended with a proposal for the following additions:
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• An allowance in the requirement for interleaving for workload - the cooking task was not a particularly high workload task and it was thought that consequently, the BP of Free Time was observed.
• In addition to considering the degree of experience with the individual task, the previous experience with the actual set of tasks may be important. In the case of cooking, there was no previous experience with the actual meal to be cooked.
The job of computer operator is such that it is necessary to consider the following two additions:
• The operators do have experience with the job itself - i.e. the particular set of tasks under fairly standard conditions. This is the other extreme of second addition above. • There are other operators present. The task set which they must consider is in practice a subset of the tasks which a number of operators are concerned with as a whole. There was no strict demarcation of responsibilities, but rather the various tasks were dealt with on a more opportunistic basis. It might be expected, then, that this will have an impact on any one person’s ability to coordinate their own tasks.
3 . The Study
3 . 1 . The Chosen Job - Computer Operations
The operators who were observed, were employed by a computer centre, which provided general central computing facilities for both staff and students of a college within the University of London. The facilities encompassed both micro computers and a mainframe, with its attendant terminals. The operators were responsible for the running of the mainframe, with only limited other responsibilities.
A mainframe differs from the micro computers with which most people are familiar in several ways. Most obviously, it is much larger and typically more powerful. Rather than being dedicated to a single user at a time, it is shared by a large number at once, each one using a separate, remote, terminal in some other part of college. The suite itself, which consists of the computer and the central peripherals such as disk drives and monitors, was housed mainly in one room, with an additional room holding extra printers
The mainframe was actually made up of 5 computers, one of which was termed the
hub and formed the central control for the other machines - named the rims. Attached to these machines were numerous other devices, such as printers and plotters (these were located centrally and users had to come and collect anything they had printed), communications gateways (to the users and other computer sites in the university),
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together with terminals by which the operators themselves controlled the computer(s). These terminals were both of the more modem VDU (Visual Display Unit) type, and also the older teleprinter type. The latter have no screen, but print their output onto a continuous roll of paper. There are at least two advantages of the latter for the operators: more than the last 24 lines is available for their inspection, and any activity is audible. One disadvantage is that teleprinters are slower than the screen based terminals.
Two teams of approximately three operators manned the suite in two shifts per day (it was unmanned late at night). Their jobs consisted of a general duty to keep the machines available for users, looking after the printers and associated output and so on, with a limited responsibility for answering queries from users of a micro facility in an adjoining room. As part of this were several specific jobs, one of which was the periodic backup which was observed here.
Backing-up in general involves copying the contents of one everyday disk to some other format which is taken away to a safe place, such that if some calamity befalls the everyday copy, the data can be recovered from the backup copy. The computer in the present study had a large number of large (6) and small (15) hard disks which needed to be backed up. This was achieved over a week, using a schedule specifying different disks each day. Some backup was to tapes, whilst some was to other disks. The hard disks were all of a removable type, which meant that some could be
removed from a drive, and replaced by other disks. There were only a limited number of disk drives, which meant two things. Firstly it meant that there was a degree of competition for and juggling of these resources, and secondly that the computer had to be taken out of normal service and users excluded from using it while backup was taking place.
To minimise the inconvenience to the users, the periodic backup took place between 8.00 am and 9.30 am each day, and thus the operators were under pressure not to exceed the deadline for bringing the computer back on line.
User access was via a gateway called the DCX. The task action in the backup job was to switch this to exclude users and display a suitable message. Similarly, the last task would be to re-enable this link when everything was restored to normal. It was also the practice of most of the operators to halt and restart each of the computers at both the start and the end of the backup session.
During the backup period, one particular operator would deal with the backup itself, whilst any others would take care of less important tasks like opening the micro room for users and checking the paper in the printers. The backup operator would be kept busy for the hour or so that it took (they typically managed to beat the 9.30 deadline),
swapping disks, entering commands on terminals and logging his actions in the appropriate book, and at the same time monitoring the active VDUs and Teletypes for problems. Each backup task required both a source and a destination drive of the appropriate size (termed ‘big’ and ‘small’ in the protocols), a computer (a further constraint was that different drives were connected to different computers, but a computer could run more than one at once), and a terminal. The exact time to copy was unpredictable.
It might be expected from this description that the job of backing-up such a computer is fairly straightforward once a procedure has been learned. The job is sufficiendy complicated with unforseen problems and tasks that it is far from simply a matter of repeating a sequence of tasks from memory. This, coupled with the way it
corresponds to the current definition of multitasking, makes it interesting for the current purposes.
3 . 2 . Method 3 . 2 . 1 . Subjects
The subjects were five computer operators, going about the job of backups as closely as possible to the way they would do it normally. There were two shifts of
operators, who took it in turns to do the early shift, and therefore the backups. One of these shifts was smaller than the other, and was used first. For this reason, it was agreed that subsequent subjects would be left to do approximately the same set of tasks (i.e. those associated with the backups) and other shift members would confine themselves to the peripheral tasks, such as cleaning the printers.
The researcher visited the operators at work on several occasions prior to data collection in order to become familiar with the nature of the job. This had the added advantage of allowing the operators to become familiar with an observer being present whilst they worked.
All subjects gave concurrent verbal protocols whilst working. The subjects were all experienced at the job they had to do, with levels of expertise ranging from the shift leaders (several years) to newly trained operators (several months). All subjects were male, and aged between 22 and 35 years.
3 . 2 . 2 . Data collection
The nature of the working environment was such that video recording was not feasible - the computer room was large and crowded with tall cabinets around which the operators were constantly moving. It was decided that audio recording would be
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sufficient given its successful use in the first (cooking) study when coupled with notes made by the researcher.
To minimise the intrusion, keeping the recording as low-key as possible so that the other people with whom the subject had to interact could be assumed to be doing so normally, a small micro-cassette recorder was used. This fitted neatly into the pocket of the subject, who then wore a small tie-clip microphone. The latter could be
positioned close to the subject’s mouth, thus overcoming the problems of the excessively noisy air conditioning in the computer suite. The tapes in this recorder were long enough to last for 45 minutes on each side, so they had to be turned over at some point in the observation. The researcher was careful to do this at a moment judged to unlikely to interfere with the ongoing tasks. A second cassette recorder
was used by the researcher to record any notes and observations as they occurred during the job. Finally, the subjects were all de-briefed after each session to clear up any remaining points that the researcher had not fully grasped.
The protocol instructions were given to each subject in writing before the start of the session, and any questions were answered as necessary. The instructions themselves were based on those used in the previous (cooking) study, which were deemed to have been sufficiently successful, although it was necessary to make some small modifications (see Appendix B).
3 . 2 . 3 . Data analysis
All the protocols, and additionally the recorded notes made by the researcher were first transcribed. These were then broken up into statements associated with particular phenomena. These are presented using the framework of horizontal and vertical development and understood in terms of the current generation of the model. For a fuller description, see Chapter 4. A full example protocol is given in Appendix B, along with the instructions given to the subjects.
4 .
Results
This section presents the data in the form of protocol extracts. The extracts are grouped in terms of the BPs they support, which are grouped further according to the Horizontal and Vertical classes demanded by the Method of Chapter 2. This chapter uses the same conventions for the extracts as listed in Table 4.2. (Chapter 4).
In the small sample of operators observed, there were no large individual differences. They had all worked together for at least a number of months and the more
experienced operators (S1 and S2) had been responsible for training the others. This might reasonably account for the similarity of style. The subjects do vary a little more
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in their level of skill - S4, in particular, is less experienced than the others and this is visible in some of the extracts below.
4 . 1 . Horizontal
Horizontal development is concerned with those novel BPs which are thought to be largely attributable to the novel JAs of this particular instance.
4 . 1 . 1 . The Task set is shared with others
In this task, it was clear that the particular set of tasks under consideration by the particular operator was a subset of the tasks under consideration by the whole group. The important point is that this subset is not fixed, and it is clear that they have to make allowance in this respect.
The problem could occur in both directions - that is the operator may on the one hand anticipating doing a particular task, but find that someone else has done it (this may mean that the operator has time to spare, but further, had they known about this in advance, their planned schedule may have been different). On the other hand, the operator may have planned a schedule which relies on someone else doing something - in which case they may need to be told to do this.
E.g.:
Subject 2 is obviously aware of the other people and takes them into consideration when planning what he himself should do:
S2179 Erm, right, I'm just trying to think now (what about?) What I've got to do and what ______ has been done. I mean Bob has -_______________________________________
In the case of S4, the subject had stopped and was looking around thoughtfully. In the response to the researcher’s prompt, it is clear that he has time on his hands and is looking for something to do. Crucially, he checks what the other members of the group have done, or are doing:
S4 (Right, so what have you got to do?) Right, so all the backups are going now, so there's other things to do, not to do with backups. Is John doing the printers? ______ What I'm going to do now, is every morning we have to clean the tape drives___
The following is almost the opposite of the above two cases in that here the subject finds that what he intended to do has already been done by someone else. Not only has this other operator done one of the tasks (i.e. stopped everything), but in so doing he has prevented the subject from doing other tasks (i.e. those which would have been done before the machines were stopped).
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S3 Now the first thing that I do is to check the rims just to check that everything is going and I check the hub. Dave has stopped everything already so - 1 haven't done retries Dave (??) - well we usually do retries but we won't bother with that either. We usually do the messages first as well, but I won't bother with that either
4 . 1 . 2 . Previous experience with the task set
In the previous study, the task set (i.e. the tasks to be interleaved) was specifically chosen to be realistic but novel for the subjects. In the current study, protocols were gathered from the individuals as they went about their usual work. As with many jobs, this one involved much that was the same from one occasion to another. Consequently, it was apparent that the subjects had established routines, and that these rarely changed from one time to another, thus the same schedule could be remembered and re-used. That they were nevertheless capable of planning or scheduling a set of tasks is evidenced by the fact that they still had to make
adjustments to this schedule in the light of unforseen events, and also that they were able to verbalise the reasoning behind the learned schedule.
(This learned schedule must have originated in someone’s mind, whether it is passed from trainer to trainee, or assimilated from scratch by each trainee is unclear.)
Examples of a pre-leamed schedule:
S2271 I've just remembered that I've forgotten to put this in as going back up on here. We've only had this on for the past couple of months and it’s still not ground into ______ the system that it’s automatically there______________________________________
Note the last sentence - this seems to suggest that the subjects are aware that they develop routines for their job.
S 1 The first procedure that we do is produce a copy of the disk log________________ The way that this is phrased suggests that this is not something that he has decided to do, but rather that producing a copy of the disk log first is accepted practice - i.e. it is routine.
S3 Now the first thing that I do is to check the rims just to check that everything is going and I check the hub. Dave has stopped everything already so - 1 haven't done retries Dave - well we usually do retries but we won't bother with that either. ______ We usually do the messages first as well, but I won't bother with that either______
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This extract has been used elsewhere in this report to illustrate the need for being aware of the other people involved in the job. In the current context, the important feature is the way that the subject implies that what he does is routine (e.g.
“usually”).
That subjects are nevertheless still capable of thinking and planning for themselves is illustrated below:
53 Now if I'd been on my own, I would have tried to sort it out, but like Dave could carry on and I could do the backups, so if I'd been on my own, I would have carried on with the backups, and kept going over there and hammering away at the PCX_________________________________________________________________ The above illustrates two things. Firstly that the subject is able to amend his routine - to cope with the fact that ultimately his actions will have to be situated in a possibly novel context, and secondly that the subject can plan theoretically - i.e. he can create an imagined solution from an imagined problem specification.
54 (You can do it with 2 people?) Oh yes, you can, you can do it probably with one if you had to, but it would mean that, er (Is 2 a happy minimum?) Yes, because one ______ would have to do everything, although the backups would take priority__________
The researcher prompts the subject in response to an earlier comment about them being understaffed on that particular morning. The quote is intended to support the notion that this subject, like the one above, could react to an unexpected change in circumstances.
The operators are not blindly following a schedule which they have simply learned, rather there is evidence that they understand the reasoning which underlies it. The following quotes are intended as examples of this and thus as support for their potentially more flexible role.
S262 Yes, third out of four, so. (are you going to wait for the fourth one until one has finished?) Yes, I'll wait for those other two to finish and then I can run the other one on the hub and theoretically when that's finished that's when the backups are finished because I should have done the small ones and done all that other stuff as well._________________________________________________________________ Although this subject seems to be interleaving his activities on a fairly routine basis, he is at least able to verbalise some of the constraints underlying this routine.
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S5 ... even when there are two of us, the most important thing is to start the backups first thing in the morning, so once we have started the backups, we know they are