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Supporting “nomadic awareness” and team workingthrough visually augmenting broadcast communication

Yvonne Rogers, Harry Brignull and Mike Scaife*

Interact Lab,School of Cognitive and Computing Sciences,

University of Sussex,Brighton BN1 9QH

UKyvonner, harrybr@cogs.susx.ac.uk

* Mike Scaife died suddenly and unexpectedly while we were revising the paper. His contribution to the research was instrumental.

ABSTRACTNomadic team working involves close-knit groupscollaborating over a large geographical space performingtime-critical tasks. We present an ethnographic study of theway a dispersed team of technicians coordinate their work,highlighting the phenomenon of extraneous ‘detectivework’ – where much communication, via walkie-talkies,needs to take place when uncertainty arises in their work.We suggest one way of providing better nomadicawareness is to visually augment verbal communication.We describe a distributed system we designed andevaluated to enable dispersed users to re-represent salientverbal information on interconnected wireless handhelddevices and a large fixed display, as simple dynamicvisualizations. Our findings showed that users were able tokeep in touch and carry out their tasks much moreeffectively.

KeywordsAwareness, communication, coordination, mobility,nomadic team working, information visualization, PDAs

INTRODUCTIONMobile working usually refers to people moving around,from one office, building or space to another, as part oftheir work [2, 12, 24], mainly to meet up with others tohave discussions, make plans, monitor progress, etc.,although sometimes just to wander around to see who isabout [2, 10]. A different kind of mobility is nomadic teamworking where groups of people have to closely coordinatewith each other and be constantly aware of each other’smovements, whereabouts and activities. An example is asecurity team who have to manage and coordinate a largeevent (e.g. a presidential visit, a conference, a footballgame) by roaming a large geographical area (e.g. an airport,a convention center, an arena) while coordinating theirwhereabouts and movements with each other and a central

control base. To keep in touch with each other in this kindof setting the teams use public broadcast systems, (i.e.walkie-talkies) backed up by cell and landline phones.

While broadcast systems are generally robust and effectivefor supporting the communication and coordination needsof such nomadic teams, they do have their problems.Sometimes members miss or mishear messages andconsequently do not move to where they are needed or dowhat is required at a given time. Other times, especiallywhen a lot is happening, discrepancies can arise betweenwhat the different members understand to be the currentsituation. Establishing common ground can require muchconfirming and updating by the various team members[18]. Moreover, this kind of extraneous ‘detective work’can be very time-consuming, involving much retracing ofsteps when trying to pinpoint what is actually happening.

In this paper, we consider how to support nomadic teamsmore effectively, especially during critical periods of theirwork, where there is an increase in workload and wherecommunication problems are more likely to occur. Webegin by reporting on an ethnographic study of how anomadic team communicates and coordinates their work.Based on our analysis, we then describe how we designed ahybrid ‘ubicomp’ system, called Offloader, that combines amix of small mobile devices with a larger fixed displaysystem, providing different views of the same information.A main objective is to provide flexible access and input ofinformation about events for people both on the move andwho are co-located in a fixed space such as a control center(cf [12, 11]). Finally, we report on some usability studieswe carried out to evaluate the Offloader prototype incontext. The findings showed that visually augmentingverbal communication, through providing team memberswith the ability to track, represent and update salient eventsas interactive visualizations on handheld and large fixeddisplays was very effective. Specifically, it enabledparticipants to see at a glance the key parameters

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representing the flux of activities and team member’smovements, thereby reducing the need to carry outextraneous detective work in order to find this out.

RELATED WORKNowadays, mobile technologies, namely cell phones andPDAs, have become ubiquitous, enabling individualswherever they might be to communicate remotely withothers and interact with electronic information while ‘onthe move’. Studies of nomadic working both indoors andoutdoors, however, suggest that such generic tools are notwell suited to nomadic work. For example, nomads areoften doing something else, like hanging onto to a telegraphpole while fixing overhead wires [10] or collecting datawhile on a field study [14]. In these kinds of settings theworker’s primary task often requires the use of both hands,making it very difficult for them to interact with asecondary communication device. They also need to befocusing on the problem at hand and so are unable to divertmuch of their attention to interacting with another handhelddevice.

Various kinds of interfaces and interaction styles forhandheld devices have been proposed to overcome theseconstraints, including layered sequential screens, the use ofaudio, and physical controls that can be operated by withone hand [e.g. 3, 10, 13, 14]. A central concern is how todesign for the combined constraints imposed byminiaturization, mobility and outdoor environments [4, 14,17]. One approach has been to design minimal attentionuser interfaces (MAUIs), that reduce the information shownon the screen while trying to maximize context awarenessto enable relevant information to be displayed or played atappropriate times [14, 21]. Another approach has been todesign context-aware ‘wearables’ that do not require anyhands to interact with, but instead allows the person totrack information and have information sent to themthrough the use of GPRS, while also communicating withothers via hands free audio or video [9].

Much of this research, however, focuses on supporting theindividual doing their tasks in outdoors conditions. Here,we are interested in how team collaboration can beenhanced by using a mix of individual mobile technologiesand shared fixed displays. One of the earliest examples ofdesigning new arrangements of devices and displays forteam working was the PARCTAB system [23], developedby researchers at PARC, that used various shared softwaretools, such as Tivoli [15]. Since then, there have been anumber of attempts at combining different technologies tosupport group working, e.g. I-Land [22], eTable [19] andthe Interactive Workspace [7]. However, the focus of thisresearch is largely on supporting groups working in co-located settings and in confined spaces, like offices andsingle rooms, where contact is essentially face-to-face andstationary. There has been little research on supportingnomadic work using arrangements of integratedtechnologies.

THE PROBLEM SPACE AND APPROACH TAKENIn principle, broadcast-mediated communication allowsanyone who has a walkie-talkie tuned into an agreedfrequency, to listen in to all the messages and conversationstaking place. In practice, most walkie-talkie users developwell-honed ‘cocktail-party’ skills, attending to messagesthat are relevant to their work while remaining peripherallyaware of what else is burbling over the broadcast system.However, despite providing an effective mechanism forsupporting awareness [5] and overhearing [8] broadcastsystems do have their disadvantages; mis-hearings ormissed messages can occur, especially when a walkie-talkiebreaks up due to poor reception (such as when used in asteel building) or a team member is busy with somethingelse and doesn’t hear or relay important information.

One of the main difficulties confronting nomadic workerswhen trying to keep in touch of the latest happenings,however, is that the amount and pace of the changinginformation can sometimes be overwhelming. Moreover,different messages about the same event can be passed onby different people, some of which have been supersededby newer events. This requires the workers to engage inmuch mental juggling of information, trying to maintain acoherent picture of the latest, i.e. what is happening, whereeveryone is, where the origin of certain messages camefrom and so on. Inevitably, there are times when old orfaulty information is accepted to represent the current stateof affairs, resulting in wrong decisions being made aboutwhat to do next. Much redundant verbal repair work willthen have to take place to enable the members to realigntheir understanding [18] – all of which takes up valuabletime.

The specific problem space we are concerned with here isthe extraneous ‘detective work’ nomadic team membershave to do when uncertainty arises in their work. By thiswe mean reconciling the disparate views each teammember has of what is the current state of affairs. Typicallythis involves determining if something really has changedand what events might have intervened since the last update– all of which can be exacerbated when work loadincreases. We use external cognition [20] as our analyticframework for the field study and to inform the design of aprototype system aimed at reducing the need to doextraneous detective work. A central part of our analysisconsiders how to ‘offload’ salient aspects of transientverbal communication onto shared visualizations, that canreadily be accessed by all when needed. We propose thatre-representing such transient information as external visualtraces will enable team members to see at a glance, who iswhere and what needs doing, reducing the need for back-tracking and verbal repair work. The prototype also acts asa visual organizing tool that can be used alongsidebroadcast communication. In so doing, it can help teammembers more effectively manage the ad hoc nature of thetroubleshooting work they have to do on-the-fly.

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In sum, the rationale for our approach is based on thepremise that much of the effort and work involved inkeeping track of what is the current state of affairs can beoffloaded [20] as a visible record; one that is constructed bythe team when and where problems are recognized. Thishas value for both monitoring and planning since it can beaccessed by all concerned – while still enabling the teammembers to continue using a broadcast system as theirmain means of keeping in touch.

THE ETHNOGRAPHC STUDY: COORDINATION AMONGA/V TECHNICIANS AT CONFERENCESIn order to understand how distributed nomadic teams keepin touch and the communication problems that can ariseduring their work, we initially carried out an ethnographicstudy of nomadic team working. Two of us shadowed,interviewed and joined the audio/visual (A/V) technicianswho were responsible for organizing CHI’2001 prior andduring the event, that was held at the Seattle Conventioncenter. We took notes on the fly and having got permission,also recorded conversations that took place face to face andvia walkie-talkies, mobile and landline phones, using taperecorders and a scanner. We also interviewed a number ofconference organizers and observed technicians at work atother conferences.

Setting up and firefightingThe various events that take place at a conference, such astutorials, workshops, paper sessions and demos, have allbeen meticulously planned in advance, as to how they areto be run, what A/V support is required and how to set upthe rooms. Typically, a data projector, microphone, VCR,overhead projector and screen are set up, although itemslike wireless mikes, flip charts, cameras, tripods may alsobe requested. Large conferences can have anything from upto 50 events (rooms) running in parallel each day, eachneeding setting-up and monitoring. When the A/V teamarrive at the conference center they set up a control centerand store room to direct operations. The A/V team wefollowed consisted of a manager, deputy and tentechnicians.

A key initial role for the technicians is to try to get as muchof the equipment set up for a session in advance. Onceinstalled a main part of the work, during a conference, isdealing with the unplanned events that they callfirefighting. Examples range from a speaker demandingdifferent equipment to equipment malfunctions to settingup unscheduled events. The number and timing of these‘fires’ is unpredictable but many are last minute. Inpreparation for putting out the fires, technicians known as‘roamers’ are placed in strategic positions throughout theconference center to be on hand to receive or notice anyproblems. However, even though they are able to readilyrecognize the kind of problem when it surfaces and whatmight be an appropriate strategy for dealing with it,solutions are often complicated by contingent factors suchas particular features of the rooms or speaker demands.

Hence, a key aspect of their work involves trouble-shootingand dealing with unexpected events in unpredictable placesand times. The team need to be highly flexible; being ableto rapidly group and disband, in different locationsdepending on the exigencies of the moment. To achievethis, up-to-date information of who is where, who is doingwhat, what needs to be done, etc., needs to be continuouslyand effectively relayed between the distributed teammembers.

The communication streams and misalignmentsThere are many different routes by which problems aredetected, reported and subsequently dealt with by the A/Vteam. Speakers, student volunteers, conference organizers,attendees and the technicians themselves may all be thefirst to detect a problem. How it is communicated and dealtwith can then follow a number of pathways. For exampledifferent speakers have different ways of making theirdemands and complaints known. Some may just tell an A/Vtechnician or a conference organizer and leave it at that,whilst others will tell everyone in sight. Thus, excessivecommunication can take place, even for dealing with fairlyminor problems. To keep updated on the current state ofwhat needs fixing, when roaming and away from base, thetechnicians use a combination of public broadcasting andopportunistic face-to-face meetings. When they return tobase, they will also pass on any updates to the manager andwhoever else is in the room and, conversely, catch up withother workers’ knowledge of the current status. Themanager spends most of his time at the control center, oftenholding several conversations at once, mainly via thebroadcast system and face-to-face. Much of this updatingrelies, therefore, on opportunism and for the technicians tobe tuned into their surroundings and to bump into eachother on their wanders around the building.

Broadcast mediated communication is central to nomadicteam working. It enables rapid and efficient talk to takeplace between the technicians, allowing them to hear andkeep informed of the latest events of their own team whilealso listening in to what other teams are doing at theconference (e.g. catering, security). Such surreptitiousoverhearing can be very useful for finding out in advance ifthere are incidents or events that they will also have to dealwith (see [8]). However, not everything can be monitoredin this manner. Some information may only be passed onface-to-face and not be available for others to hear.

A problem that can arise from having both public andprivate communication streams is that they can sometimespass by each other when they really need to meet.Accordingly, certain pieces of information may not becommunicated at the appropriate time or alternatively afaulty piece is passed on instead. When discovered,uncertainty will kick in requiring the technicians to engagein detective work. Typically, the technicians and othersinvolved will try to repair the situation, by backtrackingand repeating steps, for example as shown in the excerpt inFigure 1.

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S (conference organizer in conference center over the walkie-talkie {WT}): Yeah, R, we’re having some audio/visualproblems in room 608, they said that there is a buzzing…

A (technician in control center speaks to B): Is that the roomwe already fixed?

B (technician in control center replies to A): Yeah

R (A/V manager roaming, replies to S over WT): How old isthat report?

S <reply is inaudible to all>

R (over WT): yeah, I believe 608 is already fixed.

S (over WT): Umm, someone’s been and said that theproblem was worked on but the problem was still occurring…

R(over WT): Umm, A and B head up to the 6th floor.

A (over WT): That’s the room we already fixed but we’ll gocheck

Figure 1: Example of detective work

Many of these problems arise because, of the uncertainty ofwhat is the current state of an activity or event. Techniciansare constantly dealing with multiple jobs and tasks, whilespeakers and attendees may not know something has beensorted and continue to relay their concern to the conferencecenter. This can be exacerbated when voices start breakingup over the walkie-talkies due to the reception deteriorating(caused by a number of environmental factors) and wherethe team members have to resort to using their cell phones,meaning that the others are cut off from overhearing thatconversation, as it is transformed into a privateconversation.

Furthermore, for individual roamers, there is noindependent, up-to-the-minute external trace of theinformation available for them to consult if they shouldneed to check with what is supposed to be the case andwhat speakers, etc., think is the case. What they do have arepaper flowsheets generated from a central database, whosecurrency depends on when they were printed out. Whileregularly updated by the manager, the distribution of thisinformation as hard copies may take a long time or nothappen at all as shown in the excerpt in Figure 2.

Hence, a core concern for the technicians is working outwhat is currently true from the disparate representationsand messages they receive of what is happening and what ismeant to be happening. As we saw in the examples above,the technicians spend much time trying to reconcile thedifferent sources of information. When dealing with suchuncertainty they will tend to err on the cautious side,choosing to do additional monitoring and checking, thatcan end up being very time-consuming, frustrating andunnecessary.

R (on WT): Ned I can’t hear you. Call me on the phone.

[Ned’s walkie-talkie keeps breaking up and it is impossible for Rto hear what Ned is saying – but it takes a while for Ned toregister this is as he can hear R fine.]

R: I don’t have those on my sheets. Who is she? Her flowchartsare from the dinosaur age you know!

Ned: The problem seems to be that they want two wirelessmikes and the room doesn’t have them.

[R looks at the top of his flowsheet to see the date of theversion]

R: Your revised should say around 22nd. Hers are from godknows when. December. Things have changed since then.

Figure 2: Examples of discrepant external representations

OFFLOADER: A DISTRIBUTED UPDATING ANDTRACKING SYSTEMOur analysis highlighted the many ways verbal updatingtakes place, how broadcasting and overhearing are centralto updating and how diverse communication pathways canbe. This results in a high degree of mental tracking that thetechnicians need to do in order to work out what needs tobe done, who is doing what and who knows what.Furthermore, it can get confusing as to what really is thecurrent state of affairs; what is old news and what hassuperseded that. The team members have to rely ontransient verbal information to do this mental juggling,which can make it difficult to get the full picture of what isgoing on. We argue that such nomadic awareness could beimproved if salient aspects of it could be transformed into amore permanent visible trace. In so doing, the updating andtracking could be supported both by talking and an externaldisplay, updated in an immediate way. This could beachieved by developing a system with synchronizedpersonal mobile devices and a large shared fixed display,where information is moved between them.

Designing OffloaderThe design of our system was based on input from ourtheoretical framework, external cognition, and the detailedrequirements obtained from the fieldwork. A centralconcern was how to design a distributed system that coulddisplay critical components that were normally onlyconveyed through verbal communication. In particular, wewanted to develop a system that could offload some of themental effort required in tracking and updating, and therebyreduce the need for detective work.

The conceptual model: Our system, called Offloader, wasdesigned based on the core activity of maintaining a sharedlist of the status of problems, i.e. what problems arehappening where, who is dealing with them and how urgentthey are. A list is a very familiar organizing structure that iswell understood by people as a means of identifying,prioritizing and keeping track of things to do and what iscurrently being done [6]. It is also very good atconstraining a problem space in terms of representing it asa linear sequence of items. (cf the way paper strips are usedin ATC). This can help show at a glance the priority ofitems (using the top and bottom of the list as anchors) whathas been done (crossing out or removing items from thelist) and what else needs doing (what is left in the list andwhat else is added). The conceptual model of a list,therefore, was used as the basis for the design of both themobile, ‘pocket-loader’ part and the fixed ‘wall-loader’ partof the system. Problems and the way they are solved arerepresented as ‘jobs’, across both pocket-loader and the

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wall-loader. The conceptual model for each component wasthen built up further with other features.

The wall-loader: For the wall-loader display, informationabout the jobs is integrated with schematic spatio-temporalrepresentations of the floorplan layout of the building and arota of the equipment needs for each session. Hence,different kinds of information are provided on the samefixed display, enabling the users to compare existing plansof the day’s events with overlaid representations of theunexpected events as they unfold. In so doing, our goal wasto enable the users to be able to integrate readily thevarious pieces of information needed to make rapiddecisions.

The wall-loader was designed to be used as a large touch-screen display, with additional keyboard input, mounted ona public wall in a central location. The display is dividedinto three parts; current plan views of the day’s events isshown the upper left corner, a topographical floor plan ofthe building in the lower left side and a job status display,showing jobs as moving strips on the right side (see figure3).

Much human factors research and guidelines exist forinforming the layout of displays for time-critical tasks,where rapid decision-making is involved. Of relevance isthe proximity-compatibility principle (PCP) that promotesthe physical co-location and organization of informationthat needs to be mentally integrated [25, 26]. We took thisinto account when determining how best to integrate andoverlay interdependent representations. Specifically, thejob status display, partially shown in figure 3, was designedto convey visually how different dimensions co-vary inrelation to each other. The vertical columns representlocations in the building, while the horizontal axisrepresents time. A dynamic timeline moves down thedisplay to show where the jobs are in relative time: the jobstrips stretch down along with the timeline, as it movesdown the display. This shows at a glance how many jobsare outstanding and how long they have been running for.Each job has a default identifier which is the room it islocated in. The color of a job strip also increases inintensity the longer it remains. An alert sign is flashed upwhen a job reaches a critical state. Once a job is completedits state is changed, indicated by its color fading and thestrip no longer moving with the timeline.

In addition to designing visual information that enablesrapid-decision making to take place, we were interested inhow we could let the users be actively involved in thecreation and building up of the visualizations (rather than itall being visualized for them by the system). Externalizing,potentially allows users to offload the planning and mentaltracking required, reducing the cognitive effort involved[20]. To support user externalization we used a familiarGUI interaction mode of ‘drag and drop’. Actions that wereconsidered to be central to the planning and coordination ofthe user’s task were chosen as building blocks. Forexample, a new job strip is created by the user selecting a

color-coded icon from a palette on the left side of thescreen and then dragging it over to the appropriate columnin the job status display area. The user can then add furtherdetails, by typing in comments into the job strip. Teammembers are also represented by easy to identify cartoonicons of people’s heads, with their names underneath; againthese are dragged off a palette and overlaid on a job strip orany of the other columns, to represent that person’s currentor planned location. Moving the icons around can also helpusers optimize their plans of which people to designate toproblems – in the same way that physically movingScrabble pieces around helps when trying to construct thebest word.

Figure 3. Part of the visualization used in the fixed display,showing technicians superimposed on job strips as part of achart, with location and time elapsed as its axes.

This way of superimposing representations of differentdimensions also allows users to see at a glance who isworking on what and where all the team members are –something which is very hard to do just ‘in the head’.

The pocket-loader: Information is represented on thepocketloader as minimalist representations, in the form oftext-based, to-do-lists and problem reports. The pocket-loader was designed to be run on a PDA that has a largecolor display and stylus-based entry.

The interface was designed to provide up-to-dateinformation about the availability and progress of jobs aslists and allow rapid data entry about jobs. Informationabout a job is recorded and displayed via hotlist menus andpre-ordered forms. As with the wall-loader, people areidentified by their unique icons, which appear next to alisted job to indicate they have been assigned to it (seefigure 4).

How Offloader augments existing work practicesOffloader was designed to augment existing work practices,providing the opportunity to record a visual trace of salientevents. As such a key requirement is that it should belightweight to use in conjunction with existing ways ofworking.

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When a job strip is created by the manager on the wall-loader, it is automatically broadcast over the pocket-loaders, via an auditory beep. Similar to distributed cabbiesystems, any technician can accept a job by selecting the‘accept’ button on their pocket-loader. Who accepts willdepend on their proximity to the job and how busy they are.If no-one accepts then the manager can work out who isnearby from the location of the character icons on the wall-loader display and then call them up on the walkie-talkie.Once accepted, the status of a job changes to ‘in progress’throughout the Offloader system, indicating when and whohas accepted a job. If a technician finds they need morehelp, they can change the status of the job they are workingon to ‘further assistance’. The status of a job can also bechanged to ‘on hold’ if a technician is interrupted and needsto work on another job.

The following scenario illustrates the potential benefits ofthe Offloader system in terms of being better able to keeptrack of events and seeing at a glance the status of events.

Scenario: Bill, a roaming technician, is approached by astudent volunteer in a real panic. She tells Bill that apresenter cannot get their PowerPoint presentation to workin room 206 with the data projector provided. The sessionis scheduled to start in ten minutes. Bill briefly tries to fix ithimself but discovers that the presenter’s laptop isunfamiliar. He decides he needs further assistance. Usinghis walkie-talkie, he calls up Ed in the central office anddescribes the problem. Ed decides that the job is criticaland enters it as a job strip onto the wall-loader. At the sametime, he calls up Joe, a laptop expert. Joe stops what he isdoing, agrees to sort it out, selecting ‘accept’ on his pocket-loader. He presses the ‘on hold’ button for the job he iscurrently doing (trying to find flip charts that someone hasmoved). The flip chart job appears on the wall-loaderscreen as ‘on hold’. Ed notes that this is non-urgent but willneed solving in the next half an hour. He move’s Joe’scharacter icon onto the job strip for room 206. Elsewhere,technician Don, on the second floor checks his pocket-loader, notices the change of status to Joe’s flip chart joband decides he can help out. He sends an accept message tothe database and calls up Bill on the walkie-talkie to let himknow.

Evaluating OffloaderBefore implementing such a complex ‘ubicomp’ system, itis important to carry out usability studies to determine howthe different components will be used in relation to thekinds of activities users are going to be engaged in [1].Moreover, we had designed a system that initially requiredall the users to carry out additional work. Such an overheadis usually considered to be problematic in CSCW research.Here, however, the additional work was designedspecifically to reduce the need to do extraneous ‘detectivework’ that was found to be common in nomadic teamworking. Our intention was to enable users to create forthemselves a greater nomadic awareness of the goings on intheir working environment.

To simulate a nomadic work setting we used Wizard of Ozexperiments. We also used remote interactivestoryboarding to get feedback from the roaming technicianswe had studied as to whether they thought our designwould be beneficial to their work.

Remote interactive storyboardingThe team we had observed in our ethnographic study wereconstantly on the move, making it difficult for us to have aface-to-face session with them to get their comments on ourdesigns. Instead, we decided to use a remote interactivestoryboard technique, where we developed two scenariosfor the Offloader system, that were drawn in an accessiblecomic-book style by a graphic designer. They were createdin Microsoft PowerPoint, with the intention of allowing therespondents to add their feedback. The storyboard was sentto the manager at AVHQ. He then held a ‘crit’ session withmembers of his team, where the technicians were asked toimagine using the Offloader system during a firefightingsession, to think how useful it would be for them andwhether any problems might arise in using it. They wentthrough the pages of the storyboard, and added theircomments alongside our scenario as to what else wasneeded, what was unnecessary and what was unclear (seefigure 5).

Overall, they were very positive about the proposedOffloader system, finding the idea of having an up-to-datevisual record of events very useful. For it to work,however, they suggested there needs to be a high level ofcontext awareness, where changes taking place at thevarious locations are regularly updated on the Offloadersystem. They also made a number of suggestions about thekinds of parameters that they considered were important tobe represented visually. These included the need for alertindicators and the start and end times of events. They alsothought that inputing data about ongoing events would notinterfere with their workload, provided the number of stepswere minimal.

Figure 5: Sample from the interactive storyboard sent to thetechnicians with their added comments.

Wizard of Oz experimentsIn light of the technicians feedback, we redesigned certainfeatures of the Offloader, in particular changing which

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features to make salient in the visualizations. In order toevaluate how the wall-loader and pocket-loadercomponents of the system would be used in situ we thendeveloped two separate software prototypes that ran on (i) alarge back projected interactive display and (ii) a PDA. Themain objective of these usability studies was to determinewhether the opportunity to create and manage interactivevisualizations helped users manage and track problemsheard via broadband-mediated communication, especiallyduring periods of high workload.

The wall-loader simulationA simulation of managing an event was devised that couldbe run in our university building, as it was not feasible todesign a study based around organizing a conference.Furthermore, we were interested in determining whetherour claims about the benefits of providing interactivevisualizations were generalizable to other nomadic worksettings. The design of Offloader was adapted to match thedemands of the different task setting. It was developedusing Macromedia Director.

We devised a scenario where a security team wereresponsible for checking the security of the universitybuilding prior to a visit by a VIP. Participants (includingreal supervisory security guards/ porters for the building)were asked to imagine they were in charge of running thisevent. Specifically, they were required:

• to allocate their team to roam certain parts of the buildingto deal with any reported incidents in manner thatmaximizes their productivity• to keep track of all reported incidents to check they werebeing dealt with• to ensure that all incidents were dealt with before the VIParrived

Six other stooges (‘roamers’), were asked to pretend to bethe security guards roaming the building. They wererequired to sit together in a room away from the participant,communicating with him or her via a walkie-talkie. Theywere asked to follow a script, detailing a sequence ofincidents to be reported at specific times, which they weresupposed to have discovered while roaming the building.These ranged from minor events (e.g. coffee spilt incorridor) to severe events (e.g. suspicious package in thearea). The script was written in increasing complexity, withmore incidents happening in parallel towards the end of thestudy. The roamers were also required to report, via thewalkie-talkie, what they were doing (e.g. switching jobs,completing jobs). The participant could also communicate,using the walkie-talkie, with any of the roamers at any timeto allocate jobs and find out what they were doing

The wall-loader simulation was set up in front of thecontrolling participant and projected onto a large verticaldisplay (see figure 6). Six sessions were run with differentparticipants. To compare the findings, two further sets ofsix sessions were carried out with participants doing thesame task, but without access to the Offloader system.Instead participants either had to carry out the task in their

heads (no externalization allowed) or create their ownrepresentations, being provided with pens, paper, printedfloor plans of the building and stickies (paper and pencil).

Figure 6: Photo of the wall-loader simulation in action

All sessions were videoed and the participants interviewedafterwards. As this was only intended as a usability study, itwas considered that six sessions per condition wassufficient (It is generally accepted within HCI, that 4-6users is sufficient when doing usability studies, [16]).

Main findings: A main finding was that the participantswho used the wall-loader prototype found it much easier toplan, manage and coordinate their work compared withthose the paper and pencil or no externalization groups.This was most marked when several critical events had tobe attended to in parallel. The users who were in the Wall-loader condition made far fewer calls to the variousroamers on the walkie-talkie to check what they were up tothan either of the other two conditions.

From the video data, it could be seen that the participants inthe Wall-loader condition often moved the people iconsaround when talking over the walkie-talkie, sometimesplacing them back and moving different ones to the jobstrips. They also continuously scanned the wall-loadervisualization throughout the sessions, and on noticing a jobgetting ‘critical’ called up the roamer responsible for it, tocheck up on progress. This happened much less in the othertwo conditions (since they were not reminded), makingthem much more prone to committing errors.

To examine in more detail the kinds of communication andproblem-solving that took place we analysed the kinds ofutterances spoken by the participants during each of theconditions. We classified them in terms of four main types:

(i) instructing others to do something e.g., “go to room 7and help Sam”

(ii) monitoring ongoing progress, e.g., “How’s the clean-upgoing?”

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(iii) committing errors, e.g., where roamers were sent to thewrong location or where they were assigned jobs when theywere already busy

(iv) requests and clarification, where the participant wasn’tsure what was going on, e.g., “what’s happening outthere?” and “havn’t you done that already?”

The first two categories give an indication of how well theparticipants are managing their task. The last twocategories give an idea of when the participants are notcoping well, and which indicate the need for more detectivework. Specifically category 3 shows the amount ofincorrect decisions made by the participants about what todo, while category 4 is indicative of the repair workinvolving the participants working out who is where, whysomething has not happened, when it should have and soon. (Other kinds of talk and banter were excluded in thisanalysis).

Figure 7. Breakdown of utterance types across the threeconditions: wall-loader simulation, pen and paper and noexternalization

As the study was intended to give an indication of thepotential value of the Offloader system for providing betternomadic awareness, we decided that simply comparing themeans across conditions was sufficient. As Figure 7 showsthere are quite different trends in the communication thattook place across the three conditions. A main finding wasthat the frequency of instructing (category 1) andmonitoring (category 2) was greater for the Wall-loadercondition than for the other two conditions. Conversely, themean number of errors made (category 3) and requests andclarification (category 4) were substantially more in the penand paper and no externalization conditions.

While the amount of instructing and delegating of jobs isroughly the same between the Wall-loader and pen andpaper conditions, it was much less for the noexternalization group. Instead the participants in thiscondition spent considerably more time asking the roamersquestions about what was happening (category 4). Thissuggests that they had to do much more detective work to

keep track of events and were susceptible to making moreerrors.

Dynamic visualization versus own externalizing: In theWall-loader condition, the participants were able to quicklydevelop an efficient and systematic procedure oftransforming what was being relayed to them verbally intoan external representation of the state of affairs. Hence,there did not seem to be any problems of interferencebetween using the two modes or any translation overheads.The paper and pencil group also managed to externalize theverbal information quite effectively. However, the extraeffort of doing so sometimes took its toll, especially whenthe workload increased. Participants often hurriedlyscribbled down notes, as they attempted to re-representwhat was being relayed to them over the walkie-talkie,while at the same time deciding what to do. When trying tomake changes to existing activities, they would typicallycross out what they had previously written and write thenew information elsewhere. The longer the study went onthe more difficult it became for the participants to make outwhat they had written was relevant. From the video data,several participants could be seen to be ‘hovering’ their penover their externalization, trying to work out whatconnected with what. Having so many crossing-outs alsomade it difficult for them to organize the latest informationand give it any structure. This made it much harder forthem to see connections between their differentexternalizations. In their post task interviews severalcommented on this problem, e.g., one participant said“When it got busy my notes did get confusing... there’sonly so much you can write on a page.”

The Pocket-Loader SimulationThe focus of the previous study was whether augmentingverbal communication with a dynamic visualization couldincrease nomadic awareness for users in a control center toenable improved collaboration and coordination. In thisusability study, we were interested in determining how easyit is for the roamers to use the pocket-loader component ofthe system to input and track events while on the move andin conjunction with using a walkie-talkie. Previous researchhas shown it to be difficult to both input and readinformation when using a small device while walking ordoing something else. We wanted to see whether ourminimalist interface design provided sufficient structureand information for the participants to carry out their tasksand whether stylus input, which is the standard input modefor most commercial PDAs, was acceptable.

A to-do list application was developed in PersonalJavawhich ran on an iPAQ Pocket PC. It provided the option oftext input, via a soft keyboard on the screen and menuselection via stylus tapping. A walkie-talkie was attached tothe back of the iPAQ, enabling participants to hold bothdevices in one hand. Six participants were asked to roamaround the building looking for suspicious objects andanything unusual. Various incidents were set up (e.g. spiltcoffee, loitering students) which the participants had to

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record on the iPAQ, while also communicating them totheir manager, using the walkie-talkie.

Findings: Participants found it relatively easy to look uppre-stored information on the handheld device whilemoving around. The participants were able to tap throughthe menus and to-do-list to find the information theyneeded at a given stage of the task. They also had noproblems switching between using the to-do list applicationand talking over the walkie-talkie. As might be expected,the participants found it much more difficult to type incomments using the stylus and virtual keyboard on thescreen, while on the move but also when stationary. Theyfrequently made mistakes, selecting the wrong characterkeys, when trying to enter a comment. They also allcommented on how it interfered with what they were doingat the time.

Our findings confirm earlier work: pecking at tiny soft keysusing a stylus, especially while doing another task ormoving, is difficult whereas selecting from a limited rangeof menu options and icons is much easier to achieve. Thisimplies that in order for handheld devices to be usable byroamers, each interaction should only require a smallnumber of taps in quick succession. Any other demands tofill in forms, write comments, etc., are likely to bedistracting, more prone to errors and ultimatelyunacceptable by the users.

DISCUSSIONAs our research has shown, nomadic awareness requiresdifferent kinds of support compared with other kinds ofawareness that have been researched in CSCW. Teammembers, who are continuously moving around, need toinfer from a stream of messages that is being broadcastover a radio system and face-to-face, what is relevant tothem and what changes have taken place, while also actingupon this information to deal with unexpected events. Thisinvolves coordinating their efforts on-the-fly and makingad hoc decisions as to how best to collaborate, based ontransient verbal communication. Much mental juggling andtracking is demanded of the team members – all of whichinvolves considerable communicative effort. As discoveredin our field study, a compensatory strategy is to engage inextraneous detective work, backtracking and confirmingwith each other as to what is what. This tends to happenwhen uncertainty arises through team members havingdifferent understandings of what is the current state of play.

To improve nomadic awareness, we proposed providing alightweight dynamic visualization system, that enablesusers to re-represent salient aspects of the verbalcommunication as a visual form, which they cansubsequently access to find information they wouldotherwise have to rediscover through detective work. In sodoing it provides a way of externalizing the current state(rather than having to try to memorize it all) together withproviding a resource that can help users in their planningand decision-making.

While the provision of visualizations and other displays isde riguer for most time-critical work in fixed ‘office’settings (e.g. emergency services, dispatch management) itis not so for nomadic settings. Instead the workers mustmake decisions and plan when doing firefighting, based ontheir memory of what is being said about the current stateof events. Our research has shown that providing alightweight system of interlinked visualizations cansignificantly help both nomadic and control-based workerskeep track of what is going on at any given time.

For our design, we chose to use a combination of handhelddevices and a fixed display to provide different views of theinformation, so that both team members in a control centerand those moving around could coordinate their actions.What is gained from having such a distributed system,compared with a single device? We would argue that amain benefit of having the two kinds of interlinked displaysis that both moving and central control staff can beinvolved in keeping the shared information up-to-date,thereby ensuring that all benefit from this kind of nomadicawareness.

So were we successful at providing an appropriate kind ofsupport for nomadic work? Is reducing the amount ofdetective work an appropriate method? Some might arguethat trying to reduce the cause of uncertainty might be abetter strategy. However, as our field study showed, this ismuch harder to achieve because of the combinatorial natureof the problems that arise and the unpredictablecommunication streams that can ensue to resolve them.Moreover, it is much harder to try to prescribe how peopleshould communicate, especially, when it involves membersof the public who are under duress. Alternatively, providinga better support system for those responsible for managingthe events would seem more effective.

Finally, were we able to design a system that couldovercome the classic CSCW dilemma, namely, do thebenefits arising from using the system outweigh the extraeffort needed by everyone to make it work effectively? Ourusability studies suggest that Offloader has the potential foroffering substantial benefits relative to the amount of effortrequired by the team members to use it. Moreover, wewould argue further: that it is the extra externalization workthat the workers have to perform which provides thebenefits, and paradoxically, when their workload is high.Memory load is reduced and the ability to externalize plansas a simple dynamic visualization helps team members intheir planning and decision-making. More events can bemonitored at the same time – something that is much harderto do without having the opportunity to externalize whathas been just said. In sum, Offloader could be of mostbenefit to team working when the need for nomadicawareness is at its greatest.

ACKNOWLEDGMENTSThis research was carried out as part of the Dynamoproject, grant no. GR/N01125 awarded by the EPSRC, UK.The authors gratefully thank Rene Audette and the rest of

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the AVHQ team for their cooperation, Mia Underwood andGreta Corke for their graphic designs and to our partners onthe Dynamo project, Tom Rodden and Simon Lock.

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