Human-Computer Interaction 3e Dix, Finlay, Abowd, Beale

exercises  -  19. groupware


We discussed the use of a group pointer in a shared editor with a shared view. Consider the advantages and problems of using a group pointer when participants have different views. How do you show the pointer if it is outside part of the document you are working on? Think also about the issues when the system is a hypertext-based co-authoring system. Is there any use for a group pointer in this case?


The purpose of this exercise is to encourage students to think of the various scenarios that can arise during group editing and to encourage creative interface thinking. Where suitable tools are available, students can create mock-ups of their solution using a drawing package, or even envisionments of specific scenarios using HyperCard or a presentation tool. Below are some ideas.
We can start off with the shared editor shown in Figure 19.8. Imagine if your colleague wanted to point to the line starting 'Thinking about'. She could select the 'group pointer' tool, at which point she can drag around an icon shaped like a hand. She moves this over the words 'Thinking about' and starts to talk about the text (using some other means of direct communication such as the telephone). As the phrase in question is on both displays there is no problem about where to display the hand: it is placed over the words 'Thinking about' on your display. (Note that the group pointer is at a different physical location on each display).

Arguably the group pointer is even more important when there are separate views than when the view is shared. With a shared view the participants can be assured that they are seeing the same thing and so can assume a shared context. With separate views the participants are likely to have various problems when they forget that the others' views are different. For example, they will have trouble with indexical expressions or with relative statements 'the thing at the top'. The presence of a group pointer can help the participants to gain a shared focus.

On the other hand, the very presence of the group pointer can encourage the participants in a false sense of shared context. One could therefore argue that when participants want to enter a period of shared focus and synchronous discussion, they also move to a shared view. However, for the rest of this answer we'll assume that the views stay different.

What do we do when the group pointer is outside of the view? For example, in Figure 19.8, your colleague might move the group pointer to the line starting 'More adaptable'. In this case, your screen cannot display the group pointer in its correct position. Various options suggest themselves.

One could have the hand icon appear at the very top of your display with the finger pointing straight upward, meaning 'see above'. Similarly, if the group pointer were below the screen the icon could appear at the bottom pointing down. If such icons were displayed then the user could scroll the screen upwards until the group focus was found. Alternatively, one could arrange that to click on the icon scrolled one to the correct position.

Instead of, or in addition to, these 'out of view' icons, one could use the scrollbar and display the group pointer's position in it, thus allowing the user to see where it is easily, and scroll there if appropriate.

In the hypertext case, the solutions depend very much on the particular style of the system. If the individual nodes are large, then even if two participants are acting on the same node they may have different views, in which case all the above measures become relevant. If the participants are looking at different nodes, then the first action of a group pointer should be to direct attention to the node of interest. In a hypertext where the node graph is shown, this can be achieved by displaying the group pointer on the node of interest. Alternatively, if the graph is not displayed, the presence of a group pointer could be shown by adding a 'go to the focus node' button, rather like the 'home' button in many HyperCard stacks.

Although it is not mentioned in the question, it is worth also considering the display of other people's insertion points. In Figure 19.8, although your insertion point is within your colleague's view, it is not displayed in any way. There is no reason why other people's insertion points should not be displayed (suitably identified) when they fall within your view and vice versa. In addition, one might want some indicator on your scrollbar to show where your colleague's current view is. Such indicators can enhance group awareness and be a focus for initiating direct communication.



Repeat the exercise in Section 19.6.1, but this time look for shared data on your system. Is the data updated by one person and viewed by many, or have you files or databases which are updated by several people? If the latter, find out what methods are used to prevent two users changing the same data at the same time. There may be no mechanism at all, a computerized one (for example, locking) or a social protocol (for example, a floppy disk is passed around).


There is an argument that bulletin boards are a form of shared data, so they should certainly be acceptable as an answer to this question, depending on their nature at your site and also on how well argued the answer is.

You are likely to come across a lot of loosely shared items, where only a small group access them. For example, the files that comprise the book Human-Computer Interaction were shared between the authors. Whether any sort of locking is used will depend on the facilities available in your installation, but typically such small-group sharing is handled by social protocols (sometimes unsuccessfully!).

Here are some more specific examples from one of the authors' sites:

There are centralised databases containing phone numbers and car numbers. The former is used in place of the internal telephone directory and the latter when you notice some lights have been left on in the car park! Both of these are updated centrally by one of the administrative staff. Changes are notified (by email) to the administrator. However, access to the information is available to all.

Each user has a 'plan' file in their local directory into which they can put generally informative remarks about their whereabouts. Typically, this might include a contact telephone number, regular appointments a simple diary, or indeed anything of interest. When another user enters the command 'finger Alison', Alison's plan file is displayed. As the file is owned by the individual user, normal access permissions apply and so typically a user can only update their own 'plan' file. However, through the 'finger' command the information is publicly available.

There are also examples of publicly updateable shared files. For example, some email groups are handled by having a file containing the email address of each recipient. Anyone can edit the file to add or remove their name from this list. (In fact, they can just as easily add or remove someone else's name!) On our system this file has no form of protection from simultaneous update, the assumption being that such updates are so rare that they will never happen (really).

The lack of shared data with locking is a reflection of the poor level of system support in the UNIX world. Users of PC-based software should be able to find examples of locking of shared files or databases.

Finally, it is worth discussing the use of implicitly shared information. For example, the 'finger' command in UNIX also tells you whether the user is logged in and, if so, where. This is information known to the system, but made available to the users in such a way as to facilitate cooperation.



a) Consider the widespread use of email. What explanations are there for its success and what lessons can be learned from its development to assist the design of other computer-mediated communication systems?

(b) What are the main issues that need to be addressed to ensure the success of email in an organisation?

answer available for tutors only

(a) Explanations may be - accessibility, familiarity of model, simplicity of concept, critical mass achieved via initially targetting identifiable community (academic). Well-understood mechanism of communication (text based).

Lessons - from some of the early problems, e.g. loss of context and emotion, losing richness of face-to-face communication - having to develop conventions and culture to compensate. On the positive side - model on familiar mechanisms, target subgroups to gain critical mass, etc.

(b) Alterations in management structures - often flattening effect from providing access both across hierarchies and up and down them. Whether this is positive or negative depends on point of view - management loses some power in favour of more flexible communication structures. Also consider critical mass, free rider problem, disproportionate effort, cooperation vs conflict, changing power structures. In each case answer should discuss typical ways of reducing effect; e.g., with free rider issue - enforce contribution or utilise peer pressure by increasing visibility.



How do you think groupware is likely to affect our lives in the future? Justify your answer with examples.

answer available for tutors only

There are many possible issues. Answer can focus on email and the ease of communication - but could be anything reasonable. Should assess its impact in terms of widening social group, electronic village, also issues such as addiction and loss of face to face contact. Groupware is likely to integrate more smoothly as it becomes more 'incidental'. Other issues may be home working, flexible work patterns and changes in management structures.



(a) Low bandwidths and single media groupware systems reduce the transmission of back channels. How does this affect communication?

(b) Emoticons are used in text-based communication to provide information about the mood of the sender. Is there any need for such augmentation in audio or video conferencing? Justify your answer.

answer available for tutors only

(a) Answer should define back channels. Because they fill in gaps in the conversation - backing up the utterances - they are critical for turntaking and establishing context. Thus there is a need to introduce explicit mechanisms for doing things that occur naturally through back channels, e.g. turn-taking - provide explicit request floor/relinquish floor protocols.

(b) Emoticons (or smilies) are symbols introduced into text-based communication to indicate mood. They are needed because of the lack of back channels, facial expressions, tone of voice and gesture, which indicate this in face to face communication. They are only effective if participants share understanding of their meaning. Video and audio are richer than text but not as rich as face to face. Answer should discuss what is lost with each of these media and how these might be compensated for within the media.



How effective is the time/space matrix as a tool for classifying and analysing groupware?

answer available for tutors only

Answer should describe time/space matrix and its use as a tool for classifying and analysing groupware.

Dimensions: co-located/remote and synchronous/asynchronous. Co-located - users in the same place. Remote - users in different places. Synchronous - users working at the same time. Asynchronous - users working at different times. So there are four cells in the matrix.

Example groupware systems: co-located/synchronous - meeting rooms; co-located/asynchronous - argumentation tools; remote/synchronous - video conference; remote/asynchronous - email.

It is effective to a degree, but limited, as several groupware systems fall across the cell boundaries. Answer should discuss this and possible extensions to the matrix - synchronized/unsynchronized classification, concurrent/serial access.



What is meant by the terms control and feedback and feedthrough in the classification by function framework?

answer available for tutors only

Control and feedback is a two-way flow of information: control from participants to artefact; feedback from artefact to participants. Information can be communicated between participants.

Feedthrough is information passed indirectly from one participant to another through the manipulation of the artefact.

Answer should discuss the importance of these two as a form of indirect communication, using examples such as moving furniture or passing papers from person to person in a meeting. A good answer will compare them to more direct communication. Students can think of examples from domains they know about, for example, a car driver will see other drivers' signals (a form of direct communication), but also will observe their road position and infer their intentions (communication through the artefact).



Distinguish between direct and indirect communication. How can each be supported in groupware?

answer available for tutors only

Direct - computer mediated - e.g. email, video conferencing, bulletin boards.

Indirect - communication through the artefact - shared applications mainly.

Answer should discuss a range of applications and comment on issues such as feedthrough, common ground and shared understanding.



Identify three types of shared application. What are the main issues that need to be addressed in the design of these applications?

answer available for tutors only

Any three valid examples, e.g. diaries, authoring systems, PCs, etc. Issues to be addressed depend on the applications chosen, but may include privacy, control, lack of shared context, deixis, locking, social protocols, etc.



How far do technological factors limit what groupware can achieve at present? Suggest an example of groupware that is limited by factors other than technology.

answer available for tutors only

For synchronous communication a big issue is bandwidth: quality of video images, for example, and the need for better communication channels and compression techniques. Furthermore many people only have intermittent connections meaning they cannot be contacted at will. Other, more prosaic, limits for asynchronous communication include incompatible document and email attachment formats!

Some technologies that are available and working (such as text-based conferencing and low-cost desktop video) are more limited by social issues such as privacy concerns.



What are the two main architectures used for groupware systems? Identify the strengths and limitations of each and suggest how they can be resolved.

answer available for tutors only

The two main architectures are client-server and replicated.

Client-server: one set of data/programs, no updating problem; but poor feedback, network bottlenecks and problems with server failure.

Replicated: repetition of data/programs therefore version control problems; but much lower network traffic.

Various forms of locking ease both: in client-server the user with the lock can update a local copy which is sent to the server at the end of a transaction, in replicated architectures locks make the peer-peer update algorithms far easier - however, locking reduces the fluidity of cooperation and may reduce the rate feedthrough. Another solution is to take a hybrid approach. The answer should explore which aspects are best handled by which architectural element.

Look at the papers linked from chapter 19 on the textbook's web site for more about these issues.



A company has offices in New York and London. They are considering using some form of video to supplement their existing email, fax and telephone communications.

(a) Discuss the options available and potential advantages and problems they may encounter.

(b) How would your advice be changed if the two offices were in London and Sydney Australia?

(c) Email and video are 'just' electronic substitutes for face-to-face conversation. What radically different forms of groupware might the company consider - justify your answer using examples and appropriate theoretical frameworks.

answer available for tutors only

(a) options include:

(b) The working days in London and Sydney hardly intersect, there being an 11 hour time difference! This means that synchronous video conferencing involves, at best, unsociable hours at one end.

Asynchronous use of audio/video annotations to shared documents may be more appropriate for many purposes.

(c) options:


EXERCISE 19.13 [extra - not in book]

(a) 'Real action is situated action.' Is this true and how does it affect the evaluation of groupware?

(b) Why is it harder to evaluate groupware than single user systems?

answer available for tutors only

(a) Answer should define situated action. Context is vital since it is part of the activity of the group. Cooperation is dependent on the formation of groups, which cannot happen properly out of context. Evaluation must assess support of cooperation and must therefore consider context.

(b) Should refer to choice of method, context and situated action, variation within as well as between groups, the complex issue of who benefits. Should discuss possible solutions - any reasonable ones acceptable - perhaps extending methods such as cognitive walkthrough, or using ethnographic methods.


EXERCISE 19.14 [extra - not in book]

How far does groupware facilitate home working? What factors are likely to influence the acceptability of this mode of working?

answer available for tutors only

The main obstacles are social and managerial - the technology is available for distributed groupware systems. Problems arise from the 'invisibility' of the worker - the assumption may be that a worker who is not present is not working. Also the worker may be overlooked in promotion because of lack of physical presence. Workers may feel that they miss out on the social element of attending a work place. Some groupware systems, e.g. video-based, counter this by facilitating a sense of engagement and active social participation. The advantages of home working are economic and ecological. Economic: trained staff are not lost when family commitments require them to be at home; office space is not required. Child care requirements are reduced. Ecological: travel is reduced with beneficial environmental consequences; less power is required to maintain large office complexes (but more may be required at home). Answer should weigh these issues to reach a conclusion.


EXERCISE 19.15 [extra - not in book]

What are workflow systems and how can they be supported using groupware?

answer available for tutors only

Workflow should be defined (automate flow of information through an organisation) and an example given (e.g. processing a form). Examples of groupware support are Coordinator and Notes - discussion could compare these approaches and discuss the problems of rigid structuring implied by some workflow systems (e.g. Coordinator) and the notion of views and environmental cues (such as in Notes).


EXERCISE 19.16 [extra - not in book]

"Email is an example of asynchronous-remote groupware supporting direct communication." What do you understand by the above sentence?

answer available for tutors only

(a) Email is received some time after it is sent and doesn't require users to be working at the same time; it is therefore an asynchronous (different time) groupware.

Email may be sent to people anywhere in the world; it is therefore primarily a remote (different place) form of communication.

Email is a form of direct communication, as users explicitly send messages, as opposed to indirect communication when, for example, users share files.

A good answer may note some caveats to the above - email can be used between people in the same office (local rather than remote) and with very quick, almost talk-style, interaction (synchronous). Furthermore, the sending of attached documents may form part of an indirect communication through the artefact.


EXERCISE 19.17 [extra - not in book]

Recall the diagram in this figure is called the 'time–space matrix'

Figure. Time–Space Matrix

  1. Give a short definition of each of the headings
  2. For each of the four areas of the diagram, give an appropriate example of everyday communication or cooperation.
  3. Explain briefly where you would place the following in the matrix: Facebook wall, internet chat, Twitter

answer available for tutors only

  1. co-located – people same place
    remote – people at different places
    synchronous – people at same time
    asynchronous – people at different times
  2. synchronous co-located – face-to-face conversation
    synchronous remote – telephone
    asynchronous co-located – post-it or other note
    asynchronous remote – letter
  3. internet chat – synchronous remote because you usually use it for someone on a different machine, but need to be sending and receiving at the same time
    Facebook wall and Twitter – both asynchronous remote, as you don't expect to be in the same place, and you often see updates long after they have been posted


EXERCISE 19.18 [extra - not in book]

Define the following three terms: Make sure that your definitions clearly demonstrate the differences between them.

answer available for tutors only

Different properties of a network/telecomms channel


EXERCISE 19.19 [extra - not in book]

Site X on a network has connections to 4 other sites A, B, C and D
The connections have the following characteristics:
            site X – site A            high bandwidth            low latency            low jitter
            site X – site B            high bandwidth            high latency            low jitter
            site X – site C            low bandwidth            low latency            low jitter
            site X – site D            high bandwidth            low latency            high jitter

  1. Comment on the suitability of these connections for the following media types:

    (a) audio-conference (e.g. telephone style chatting)
    (b) live interactive video-only connection (e.g. web cam)
    (c) streaming HI-FI audio (e.g. Radio 3)
    (d) video-on-demand (e.g. hotel pay-per-view video service)

    For this part assume that there is not enough memory available to provide any buffering.  Make sure your answer clearly states the effects on the users, not just technical effects.

  2. Describe how buffering might improve/alter any of the above?
  3. An Internet-based collaborative graphics application includes a shared electronic whiteboard where participants can each annotate and manipulate a high-resolution photograph .

    Two potential architectural solutions have been proposed

    • Sending each user's freehand drawing actions (individual mouse movements) to a central server
    • Download an applet and do drawing actions on a local copy of the whiteboard contents

    Describe advantages and disadvantages of these solutions with regard to potential deployment on:

    • network connections similar to site X–B
    • network connections similar to site X-C

answer available for tutors only

  1. This answer may be organised as media within sites (as here) the other way round, or a mix.

    X–A – high bandwidth, low delays and low jitter – good for everything!

    X–B – high latency will behave badly with both audio and video for interactive conversations (a) & (b).  In particular, normal conversation has very small gaps (fraction of a second) which are used by participants to hand-over to one another.  The participants will have problems similar to trans-continental satellite links. The high latency will not hinder streaming video/audio which can simply be slightly delayed.

    X–C – low bandwidth – will mean high compression and/or loss of quality.  This will rule it out for Hi-Fi audio and high quality video.  Interactive audio may cope (depending on how low the bandwidth) and web cam can simply have reduced frame rate and resuloution.

    X–D – high jitter – (without buffering) will mean that both interactive and streaming audio will be badly affected (we can not stand delays/missing parts of speech).  The interactive video will simply occasionally have broken frames which is acceptable.  Depending on the level of jitter this will probably mean the quality is too bad for hotel video application.

  2. Buffering can be used to change jitter into delay (there are various diagrams of this in the course notes, or they can simply describe why).  This effectively means that X–D can then be used for streaming audio/video, but still not suitable for interactive audio except at 'trans-Atlantic' style quality
  3. In case X–B, the applet based solution would be necessary to achieve good interactive feedback for free-hand drawing.  However, applet security would mean that the server would need to sit on the same machine as the web server (or need signed applet).  Also the software will need to be more complicated as there will be the possibilities of race conditions when updates are done simultaneously by different participants.  Feedthrough will also be poor.

    In case X–C, the central server solution may be chosen as the low latency and jitter mean that it can give fully interactive feedback even for mouse movements (ideally students may quote figures of around 200 ms maximum round trip feedback time for this).  This will have an easier implementation.  There may still be problems however in updating photo images on the individual displays, perhaps a delay when the application is first launched as the photos are downloaded over the low bandwidth connection.  Feedthrough better.


EXERCISE 19.20 [extra - not in book]


answer available for tutors only


Individual exercises

ex.19.1 (ans), ex.19.2 (ans), ex.19.3 (tut), ex.19.4 (tut), ex.19.5 (tut), ex.19.6 (tut), ex.19.7 (tut), ex.19.8 (tut), ex.19.9 (tut), ex.19.10 (tut), ex.19.11 (tut), ex.19.12 (tut), ex.19.13 (tut), ex.19.14 (tut), ex.19.15 (tut), ex.19.16 (tut), ex.19.17 (tut), ex.19.18 (tut), ex.19.19 (tut), ex.19.20 (tut)

Worked exercises in book


Find out how many different forms of direct computer-mediated communication are available on your system (start with email). Are they heavily used, and if so, where do they fit in the time/space matrix (Figure 19.9) and its refinement (Figure 19.10)? [page 694]

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