1

The History Tablecloth: Illuminating Domestic Activity

William Gaver1, John Bowers2, Andy Boucher1, Andy Law1, Sarah Pennington1, Nicholas Villars3

1Goldsmiths CollegeNew Cross, London SE14

initial.surname@gold.ac.uk

2University of East AngliaNorwich, UK

jmb78@btinternet.com

3Lancaster UniversityLancaster LA1 4YR, UKvillars@comp.lancs.ac.uk

ABSTRACTThe History Tablecloth is a flexible substrate screen-printedwith electroluminescent material forming a grid of lace-likeelements. When objects are left on the table, cells beneaththem light to form a halo that grows over a period of hours,highlighting the flow of objects in the home. TheTablecloth explores an approach to design that emphasisesengaging, open-ended situations over defined utilitarianpurposes. Long-term deployment of the History Tableclothin a volunteer household revealed complex ways thatpeople experienced and interacted with the Tablecloth.Beyond evoking reflection on the flow of objects over aparticular table, the Tablecloth served as a ground forinterpretative reflection about technology, an asset forsocial interaction, and an aesthetic object. Even behaviourswe saw as system errors were interpreted by the users asinteractively rich. Their experience highlights the subtletyof domestic ubiquitous computing, illustrating alternativesto traditional views of technology’s domestic role.

Author KeywordsDomestic technology, information appliance, ubiquitouscomputing, interaction design, aesthetics

ACM Classification KeywordsH5.m. Information interfaces and presentation (e.g., HCI):Miscellaneous.

INTRODUCTIONThe increasing proliferation of affordable microprocessors,sensors, actuators, displays and wireless networking overthe last several years has given rise to a strong push for newforms of digital technology to enter the home. Visions forhow this might evolve differ both in the technicalinfrastructures that are foreseen and the basic values and

particular applications that are imagined [12, 13, 14].

What most domestic systems share, whether they areintegrated centres for entertainment or distributed systemsfor tracking older people, is an implicit or explicit narrativeabout what they are for. Through their interfaces and formdesign, their packaging and documentation, and thescenarios of use conveyed through marketing, technologicalsystems are designed to communicate how they are to beused, the values they serve, and the likely outcomes ofusing them. By implication, they imply a user model thatextends from our capacities as system operators to the sortof people we are if we use these systems: what our valuesare, the activities we privilege, our aesthetics and culturalidentities (c.f. [5, 2]). They commodify our identities,creating representations of certain ways of approaching andexperiencing the world that we can adopt to help constructourselves. At a larger level, then, the domestic technologiesdeveloped in the research world and sold in the marketplacehave cultural repercussions. They both reflect and shape theexperience of home through the perceptions they reify andthe actions they afford.

The way that current and emerging technologies representand constitute the home may be critiqued on severaldifferent grounds. To begin with, we may believe simplythat they misrepresent the experience of home, unfairlyemphasizing some forms of engagement while dismissingothers. For instance, commercial forces encourage newtechnological products and research to address mainstreamactivities and values at the expense of more idiosyncraticones, potentially leading to increasing cultural uniformity.In response to this, some researchers have advocateddesigning for idiosyncratic or extreme users [4] [5], if onlyto ensure a flow of new ideas and possibilities to themainstream.

A different objection to current representations of the homeis that they tend to emphasise utilitarian versions of work,entertainment, and consumer activity. From this point ofview, less purposeful, more exploratory and playfulengagements in the home are poorly served by currenttechnologies. In response to this, we might focus ondesigning for homo ludens [10], people as playful creatures,to design more open-ended possibilities for engagement [8].

The argument for supporting more playful, ludic forms ofengagement itself becomes a new critique of the tendencyfor technologies to act as embodied representations of thehome, however. For inherent to the notion of ludicengagement—of playful explorations, new perceptions andreflections, etc.—is that this is not an experience to bepassively consumed, but an intrinsically motivated andpersonally defined form of engagement. This requires thatludic technologies offer a great degree of scope for personalengagement. From this perspective, then, it is the verytendency for technologies to embody a representation aboutprivileged activities and values that is problematic.

Designing for Interpretative AppropriationIt appears impossible in principle, and undesirable inpractice, to develop technologies without any embodiedrepresentation of users, settings and usage. Choosing a setof technical capabilities inherently implies rejecting others,and thus a judgment about desirable opportunities foraction. Similarly, there is no such thing as a neutralaesthetics. Choosing to avoid particular aesthetic styles (e.g.modernist, punk, childlike) is not the same as avoiding anaesthetic commitment altogether. Even if perfectly unbiasedsystems were possible, they would offer nothing for peopleto react against or be inspired by. Making statements aboutpeople and activities is an integral feature of design.

Nonetheless, several tactics have emerged over the lastseveral years for designing technologies that avoid overlyconstrained representations of users, settings or usage. Twobasic strategies can be distinguished by the way they handlethe semantic mapping between a system and itsenvironment. On the one hand are systems that leave thismapping unspecified or open-ended; on the other are thosethat specify a semantic mapping, but create ambiguityaround its extent or implications.

Semantically open-ended systems use technology to createinteractive situations without specifying their meaning interms external to the system itself. For example, TobieKerridge and Andy Law’s Media Mediators [11] are acollection of objects that exhibit remote controlledmovements such as rolling, unfurling, and opening withouta priori mapping to external events. Their intention is toexplore the connotations of these movements by askingvolunteers to determine the mappings for themselves, thusleaving open the possibility that these interactions couldmean radically different things to different people.Similarly, the Key Table [15] uses the force with whichthings are placed on a table to control the tilt of anassociated picture frame. Although this was conceived as aform of emotional expression, this mapping was(inadvertently) not communicated to volunteers, who werethus in the position to develop their own interpretation ofthe situation.

Semantically ambiguous systems use technology to respondor refer to external situations or events, but employ varioustactics to undermine a simple interpretation. One approachis to develop systems that embody representations ofexternal situations, but then subvert the authority of theserepresentations. For instance, Böhlen and Mateas’s OfficePlant #1 [1] is a robotic “plant” that uses AI techniques toassess and respond to the emotional and social tenor of itsowners’ incoming email stream. Though its configurationsand movements represent incoming email, they arepurposefully crafted to be somewhat opaque, creating an“alien presence” requiring effort to interpret.

Another tactic for creating ambiguity is to create systemsthat clearly relate to external situations without indicating ajudgment about their meaning. This creates an ambiguity ofrelationship [6] in which designers can suggest a topic forconsideration, while allowing considerable scope forpeoples’ interpretation and evaluation of the meaning itmight have for them personally. This is the tactic we usedin designing the History Tablecloth.

The strategies for designing systems that refrain fromimposing strong representations on users have differentstrengths and weaknesses. Semantically open-endedsystems promise the most latitude to users in determiningtheir own meanings, but risk failing to afford anymeaningful semantic relationship outside of the systemitself. Semantically ambiguous systems allow designers toraise issues without determining their interpretation, butneed to be sensitive in how they indicate openness for(re)interpretation lest they appear too prescriptive on theone hand, or simply nonsensical on the other.

In any case, both strategies appear promising in allowingusers the possibility of interpretative appropriation ofinteractive systems. Rather than embodying clear andconstrained representations of people, activities andcontexts that threaten to commodify our experience, theyremain more or less open to people determining their ownmeanings. In this paper, we describe a system we developedthat uses semantic ambiguity to permit interpretativeappropriation in the home, and report on a long-term userstudy indicating the range of meanings people found.

THE HISTORY TABLECLOTHThe History Tablecloth is a flexible plastic substrate screen-printed with electroluminescent material printed to form agrid of lace-like elements (Figure 1). We applied researchby the Lancaster Equator team [16] to develop a system inwhich load sensors placed under the table’s legs are used totrack the position of multiple objects on the tabletop. Whenobjects are left on the table, cells beneath them are lit toform a halo that grows slowly over a period of hours. Whenobjects are removed, the corresponding halo is designed todisappear over a period of about 30 seconds.

3

Making History VisibleThe History Tablecloth was designed to create a situation inwhich the history of objects in the home could becomeperceptually salient. There were several sources ofinspiration for the design.

First, our Equator colleagues reported an ethnographicstudy of how information moves around domestic spaces[3]. The study focused largely on tangible information (i.e.printed materials such as post) but also electronicinformation such as email (which often becomes tangiblethrough printing). Through their observations of severalhouseholds, they identified key sites that, thoughmanifesting differently in different homes, appeared acrossthose they studied. These included locations whereinformation was held on initially entering the home, placeswhere information was “processed” (e.g. mail is filtered,bills are paid, etc.), and places where information isdisplayed. These key locations corresponded to surfaces inthe home such as tables, shelves and notice boards.

This study highlighted the importance of information flowover surfaces in the home as a phenomenon relevant fordesign. It also resonated with our own informalobservations about the history of objects within the home.For instance, Figure 2 shows a sketch diagram of objectswithin the dining area of one of the authors’ in-laws. As thekey indicates, of particular interest here were the extremelyvaried time-scales of objects on the shelves surrounding thedining table. While some of the objects on the shelf, such aspost and newspaper, might be moved on an hourly basis,other objects, such as decorative vases and similar artefacts,appear not to have been moved significantly for about 20years. This tendency seemed ripe for design intervention.

In fact, earlier design explorations in other projects hadalready dealt with similar issues. For instance, one of thetwenty or so proposals developed for the Alternativesproject sponsored by Hewlett Packard [9] was called

Benevolent Poltergeists (Figure 3). This was based on theobservation that artifacts displayed around the home, oftenincluding our most emotionally charged memorabilia, tendto lose their ability to attract attention over time, becomingessentially invisible to long-term inhabitants. TheBenevolent Poltergeist would be a robot that would emergelate at night, moving items around on their shelves to newconfigurations. For instance, objects might be moved toteeter on the edge of a shelf, stacked upon one another tocreate a precarious totem, or simply ordered according tosize. Through such tactics, the device would disruptpeople’s habitual sense of order in the home, rekindlingtheir interest and sense of possession.

Like the Benevolent Poltergeists, the History Tableclothalso addresses issues concerning the movement (or lackthereof) of objects in the home. Rather than implying thatobjects shouldn’t be neglected, as the BenevolentPoltergeists do, the History Tablecloth simply makes visible

Figure 1. The History Tablecloth (design visualization) Figure 2: A sketch diagram of objects on a dining room shelf.

Figure 3. Benevolent Poltergeists: A sketch proposal fordevices to reawaken interest in overlooked possessions.

a state of affairs. The interpretation of that situation is leftto the people who encounter the Tablecloth. Some mightfeel that it is a prompt to tidy up more often, others mightbecome reluctant to move objects on the table lest theydisrupt a particularly pretty pattern of lights. Unlike theBenevolent Poltergeists, which use a strategy similar toMatteus’ alien presence [1] in service of a particularunderstanding (that objects left on shelves tend to beneglected), the History Tablecloth was designed to raise theissue of object movement without imposing a particularpoint of view. It is intended to establish an ambiguity ofrelationship for people to resolve themselves.

Developing the History TableclothThe original proposal for the History Tablecloth was for atable, not a tablecloth. The proposal showed a grid of lightsembedded in a tabletop, lighting under objects left on thetable. The sequence of sketches (often shown as ananimation) made clear that the patch of lights should growslowly the longer objects were left on the surface, and fadequickly after they had been removed.

The original proposal did not specify the technologies to beused in constructing the History Tablecloth, but the grid ofred lights clearly implied using high-intensity LED’s, andthis is the approach we took in initial feasibility tests of thetechnology (see Figure 5). We constructed a number ofgrids of LED’s both to assess the aesthetic appearance wecould achieve and to understand the technical issues ofcreating a very large grid of lights.

Although the visual appearance of the LEDs was appealing,using them had several drawbacks. First, it appeared that alarge grid of LED’s would draw too much power to befeasible. One estimate was that a full-scale table would use

around 30 amps (roughly equivalent to an electric cooker),though we might have been able to reduce this. In addition,though we experimented with a number of means to powerthe lamps, ending with a Maxim LED display driver chip, aclever arrangement would have been necessary to control afull complement. It also became clear that wiring the tablewould be a large and tedious job, and that the table itselfwould be relatively inflexible once built.

As an alternative to using LEDs, we experimented withelectroluminescent material of the sort used for, e.g.,backlighting laptop screens. This material had theadvantage of being relatively inexpensive and requiringlittle power. Moreover, we soon discovered that we couldcut the material into more-or-less arbitrary shapes, allowingus to create more interesting patterns for the tabletop than

Figure 4. The original sketch proposal for the HistoryTablecloth implied the use of a grid of LEDs.

Figure 6. Later development focused on electroluminescentmaterial.

Figure 5. Our first technical tests explored LEDs.

5

that suggested by the initial proposal. Our initialexperiments involved cutting up 50x50 mm pre-madesheets and driving them with off-the-shelf inverters (seeFigure 6).

Soon after we began experimenting with electroluminescentmaterial, we saw work by Rachel Wingfield, a graduatingtextile designer at the Royal College of Art, displayed in theannual student degree show. Her piece was a prototypecurtain with electroluminescent material screen-printedupon it in a floral pattern that could be lit in threeindependent stages. This introduced us to the possibility ofusing screen-printing to create the large-scale grid neededfor the History Tablecloth. Not only would screen-printingallow us to lay out the material much more easily than byhand, but it would allow us to create a much more intricatepattern for the piece. Thus we hired Rachel Wingfield tohelp us specify the pattern for the History Tablecloth’scells, and to liase with Elumin8, the Southampton companythat specialized in electroluminescent screen-printing.

Our initial hope had been to arrange the electronics of theTablecloth as a matrix, so that any given cell could bepowered by running current along appropriate rows andcolumns of a wiring matrix. Unfortunately, this provedinfeasible due to cross-talk among the cells, so that usingthis strategy lit up rows and columns rather than just thetarget cell. In the end, we had to specify separate printedelectrical connections to each of the 95 independentlycontrollable lights on the Tablecloth.

The final design for the History Tablecloth, then, involvedscreen-printing 5 layers of conductive ink, insulatingmaterials, and electroluminescent material onto a flexibleplastic substrate. The electrical connections ended in a wideribbon cable running from one of the ends of the Tablecloth(see Figure 7).

It has to be said that we were initially disappointed by theaesthetic appearance of the prototype Tablecloths. Most

notably, the borders between the hexagonal cells weredarker than the cells themselves, giving the appearance ofan imitation tile pattern (see Figure 7). Fortunately we wereable to solve this problem by covering the Tablecloth with asheet of semi-opaque paper that masked the offensivepattern while allowing the lights to shine through.

Using Load Sensing to Track ObjectsPerhaps the most significant advantage of deciding to useprinted electroluminescent material instead of LEDs is thatit allowed us to develop the design as a tablecloth to beused with peoples’ existing tables rather than as a completetable. This meant that instead of imposing a new piece offurniture into peoples’ homes, we could simply modifytheir existing furniture. This flexibility promised to makefield trials much less intrusive, and in the long run to opennew usage possibilities.

Developing the design as a tablecloth was also madepossible by our strategy for tracking objects on the tablesurface. As it turns out, the History Tablecloth was one of anumber of designs we developed to use a weight-tablesystem that had been developed by our colleagues at theUniversity of Lancaster ([15]; for another example of adesign using this system see [7]). This uses the differentoutput of industrial load-cells placed on table corners totrack the location of weights upon the surface. By storingthe history of weights appearing on and leaving the surface,the system is able, in principle, to do a good job of trackingmultiple objects at the same time. This ability was one ofthe direct inspirations behind the History Tablecloth.

Using the Weight Table system meant that we could modifyany table to track objects upon it simply by mounting loadsensors under the table legs. We achieved this byembedding the load-sensors in custom-designed plasticcups that held the sensors and table leg securely together.

Computational systemThe output from the load sensors was wired to a Smart-It

Figure 7. The History Tablecloth on a table, showing thehardware housing, ribbon, and a portion of the Tablecloth.. Figure 8. Detail of the Tablecloth. Note conspicuous borders.

microprocessor board also developed by our Lancastercolleagues [15]. This bridged between the weight sensorsand a dedicated PC which ran the location-trackingalgorithm, used this to track the history of objects on thetable, and send appropriate commands to the inverter usedto control the lighting of the History Tablecloth.

The computational hardware was contained in a purpose-built housing to be placed under one end of whatever tablewas used with the History Tablecloth (see Figure 7). Thehousing was somewhat larger than we would have liked,and the use of smaller computers (e.g. the so-called ‘gum-stick PC’) would allow the design of a much smaller unit tobe, for instance, hung underneath the edge of a table.Nonetheless, our design at least partially de-emphasised thefact that the system used a standard PC.

We developed a graphical interface to track the operation ofthe sensors, including the raw output of the sensors, thesystem’s hypotheses about weight locations, and thecorresponding patterns to be lit on the Tablecloth. Thisinterface was invaluable for debugging but was notpresented to the people who encountered the final design.

The system was equipped with only two control points forusers. The first, a large red “panic button” mounted on thefront of the computer housing, allowed people to reset thesystem if its internal representation started to diverge fromthe reality of weights on the table, e.g. because of erroneousreadings or missed placements or removals of weight. Thesecond was a simple power switch mounted on the back ofthe housing, arranged to allow people to reboot thecomputer and automatically restart the Tablecloth softwarein case of more serious problems.

The Best Laid Plans: Problems with the PrototypeThe basic History Tablecloth system we implemented wasreasonably straightforward. To summarise, load cells underthe table legs provided continuous data about weights onthe table’s surface. This data was used by the system to tryto determine the location of potentially multiple weights,and the history of each detected object was tracked overtime. When the system recognized that a new weight hadbeen added, the closest cell on the tablecloth was lit, and ifthe system recognized that a weight remained, additionalrings were lit over a period of about 6 hours. When thesystem saw a weight removed, the corresponding “halo”was faded down over a period of about 30 seconds.

With tuning, the prototype worked well in our studio. Buteven in this relatively controlled environment, the systemtended to diverge from its intended behaviour over time.

First, individual cells and groups of cells began to burn outas we tested the system. Sometimes this was because smallfolds in the Tablecloth caused a break in the thinelectroluminescent film. Other times, the insulating layerseemed to develop small cracks, causing a brief but

dramatic “lightening” effect across several cells as theyshort-circuited. The underlying problem was that theTablecloth was “about 10 times more complicated” thananything the printing company had made before (as theylater admitted) and the resulting prototypes were morefragile than we had expected. In fact, most of the tenTablecloths we had fabricated ended up with burnt out cellsbefore we started our field trial. Fortunately, we found thatunder-powering the Tablecloth, and mounting a piece ofglass on top to protect it, substantially decreased burn-outs,and we observed few if any during our field trial.

A more enduring problem involved inaccuracies in theobject-tracking software. The algorithm was reliable whenused carefully in our studio, but in casual use was liable tobeing misled. For instance, leaning on the table whenplacing a weight offset the registered position, causing thehalo to appear in the wrong place. When the weight wasremoved, the algorithm might fail to associate it with theoriginal placement, and the halo would remain behind.Sometimes the threshold signaling an end-of-placementevent would not be crossed, leaving the system waitingwhile other events occurred. Other times, floor vibrationstriggered spurious placement or lifting events. The endresult was that, over time, the system’s representation (andthe Tablecloth’s display) of objects would becomeincreasingly inaccurate, and because this meant that liftingevents wouldn’t be recognized, an increasing number ofcells would remain continuously lit.

We became aware of these problems while developing theHistory Tablecloth in the studio. Through careful redesignof the system, and tuning of the electronics, we managed toreduce them significantly, and hoped that a similar processof on-site tuning would help us minimize them in the field.Nonetheless, we recognized that some problems wouldremain—this was one of the motivations for including thereset and reboot switches on the prototype device.

DEPLOYING THE HISTORY TABLECLOTHWe deployed the History Tablecloth in a volunteerhousehold for over four months and conducted an extensiveprogram of empirical observation of it in situ. The intentionof this study was not just to assess the Tablecloth per se, butto gain a deeper insight into what it means to designartefacts that allow for interpretative appropriation indomestic settings. Our research strategy favoured a detailedexamination of a single home through an extended periodrather than point studies over a much smaller timescale. Byconcentrating on a single deployment we were able to seehow use and appreciation of the Tablecloth varied overtime, how it related to the rhythms of domestic life, manyof which extend far beyond the daily (e.g. seasonal feastdays and their preparation), amongst many other issues.Although we focused on a single home, more than 20people encountered the Tablecloth during its deployment.This enabled us to sample both a range of casual

7

experiences of the Tablecloth and examine thehouseholders’ encounters with it in particular depth. Incommon with much field research concerned with studyinga setting in depth, ethnographic observation formed ourcore methodology. As such methods have become anestablished contribution in many areas where technologiesare studied in real world settings, we do not give moredetails here but refer to [7] as another example of thesemethods in our own work.

The household we studied consisted of a male/femalecouple living in an apartment in the east end of London.Their living space was part of the second floor of aconverted factory that offered one large open space with aseparate bathroom. The main space (some 100 squaremeters) contained recognizably separate relaxing, cooking,working, storage and sleeping areas. It occupied the widthof the building and so had light from both sides. The coupletypically both worked from home though were often calledout to appointments during the working day.

Situating the TableclothIn consultation with the man (whom we shall call G) andwoman (B), it was decided to best deploy the HistoryTablecloth and its table in their kitchen area (see figure 9).G and B told us that the observance of mealtimes wasimportant to them and that B often worked at the existingkitchen table. It seemed to us that this spot would give themaximum chance for interesting object-traffic to occur in a

way that the Tablecloth could react to. With the existingtable removed, we sited the Tablecloth so that it could haveaccess to power and oriented it so that the computerhousing at one end would cause least obstruction. Someinitial concern was raised by B and G as to whether theTablecloth would be liable to heat damage given itsposition in a kitchen environment. Our lab testing had notconsidered such situations so we were content to find thatout in the field. We did warn of the dangers of liquid spillsnear the edges of the table in case of seepage between theTablecloth’s various layers and asked that B or G turn offthe mains power to the table if such problems occurred.

The apartment floor (the original wooden factory floor) wasquite uneven and presented some challenges for setting thetable level and calibrating the load sensing. Pads wereplaced under each table leg and the surface aligned with aspirit level. A series of tests were run and once theTablecloth reliably recognized the placement of a saucepanand its removal, things were left to run.

The Tablecloth was described to G and B as minimally aspossible. They were told that it will respond to objectsplaced on the table by lighting up and that the research teamis interested in what it is like having such an artefact in theirhome. No specific details were given about how the tableand cloth work. The reset button was pointed out bycomparison with similar controls on existing computingtechnology with which G and B were familiar, but noparticular occasion for using it was highlighted.

Domestic Objects and Their DetectionAs our experiences in the studio suggested, the HistoryTablecloth’s behaviour in G and B’s home was acomplicated mixture of intended reactions to weight withvarious false alarms, offset errors, missed pick-ups, etc. TheTablecloth responded regularly to weights appearing on andleaving the table, but its response was far from perfect fromthe point of view of our original design intent. This could,of course, be assessed in formal terms from log data andmore formal testing. What was of interest to us, however,was what G and B and their callers made of the detectionabilities of the Tablecloth, what they noticed, how theybecame sensitized to features of objects placed upon thetable and their traffic through it, and how all of thisimpacted upon their interpretative appropriation of theTablecloth. To foreshadow, what surprised us about theirresponse is that what we perceived as errors in theTablecloth’s behaviour were perceived by them asinteractive richness.

It was clear to G and B immediately that the Tableclothilluminated where a notable domestic object was placed.But within their first day of living with the table, it becameapparent that some objects would consistently passundetected (very light ones, e.g. a pencil). Some objectswere detected in a surprising and engaging fashion. A

Figure 9. The History Tablecloth in the volunteer household.

lightweight wine glass was missed on its initial placementbut became illuminated once wine was poured in.Placement of B’s laptop on the table would usually lead tosome cells in the cloth’s design brightening but as thelaptop had four ‘feet’ it could be any one of these that wasilluminated or, occasionally, a light might come onunderneath the laptop and not be visible (yet). There couldbe considerable uncertainty about what to expect of theresponse of the table to objects with an extended footprintand/or multiple pressure points.

Many real-world domestic objects are placed in a fashion offirst-one-part then another. The laptop might be placed firstedge on with just two feet in contact and then the remainingfeet placed shortly thereafter. That is, placement gestureshave an ‘envelope’ as they are executed which means that itis often not sensible to define a single moment or locus ofplacement. Furthermore, an object might have one edgeplaced in contact with the table but this edge might bemoved slightly as the rest of the object is placed.Accordingly, for this and other reasons, objects were oftenilluminated to one side of where they were actually finallyreleased. Many domestic objects are routinely ‘dragged’ orotherwise pushed across a table’s surface and this wouldalso create uncertainties and mis-detections. Indeed, objectslike small documents commonly left a trace behind longafter a new one had also appeared at the spot they had justbeen pushed across the table towards.

Pushing or leaning direct on the table might also lead to thedetection of an object, as occasionally did walking heavilyby the table on the old floorboards. Of course as the loadsensors detect incident forces, it is not possible todiscriminate between occasions where someone has justleant on the table and is maintaining their posture fromthose where an object has been placed and left. Placing aheavy hand on an object that is already there can also leadto anomalous detection (eg a new object is detected justadjacent to the existing one or the existing one is taken tohave gone once the heavy hand is released).

One should not get the impression from this that theTablecloth’s patterns of illumination were effectivelyrandom. A typical scene would be one in which someobjects were clearly encircled by light, some had beenmissed, and some light patches were close to but notexactly where the object had been placed (see Figure 10).Equally, as the patterns spread over time, more and moreobjects on the table will come to be illuminated from belowwhether they have been detected or not. This makes for anoverall relationship between objects and light that isnoticeably non-random. As such, and this is a point we willreturn to, G and B preferred the incomplete but noticeablecoincidence of the light pattern with the layout of objects.This, to them, was more subtle and intriguing, as were theoccasionally enigmatic behaviours of the table in responseto objects being placed and removed.

The nature of object detection on the Tablecloth alsosensitized G and B to features of objects and their trafficthat might not otherwise have been attended to, theirfootprint, their edges, their weight, more specifically: theirbehavioural repertoire on the Tablecloth. That is, domesticobjects themselves were interpreted from time to time in anew light, not only as wine glasses, plates, pencils, laptopsbut as variable and intriguing in how they can be detectedand illuminated.

Interpreting the LightAnother feature of the History Tablecloth’s real-worldbehaviour that we had not picked up in the studio was howits sensitivity seemed to vary over time as the population ofobjects increased. That is, a weighty object placed carefullyon the table just after reset might well be reliably detected.However, that same object placed on the table when it wasalready full of detected objects might be missed. G: “Maybeit reaches a state where it’ll stay put. It’ll get stuck andyou’ll have to press reset to get it to start being reactiveagain”. On another occasion when the table did not respondto a quite heavy bowl of tomatoes, G suggested: “with allthis weight on the table, it probably cannot sense more”. Gand B also noted that the table, once it got ‘stuck’, wasoften less sensitive to objects being removed. Occasionally(but not always), they could get the table to retain a ‘stuck’pattern but with no objects on the table. Once, we observedB working at the table with a neat pattern of illuminationaround the laptop. “But this is the pattern I made with lastSunday’s lunch!”

It is clear that G (most notably, but B too) was beginning tooffer interpretations of how the Tablecloth worked, what its‘states’ were, its operational trajectory, and how one mightintervene in this or work with it. “Maybe it’s computingthings, measuring for how long things are on, and gets lessresponsive when it builds up knowledge of what you haveon the table. Then it has its view of what you have on the

Figure 10. Complex patterns formed in practice.

9

table so it stops. But when you reset, it knows nothing so itresponds quickly.”

Our point is not to evaluate G’s interpretation as true orfalse, still less to compare it against how we wouldunderstand the table’s behaviour. Rather, it is important tonote that such interpretative activity occurs and isoccasioned by specific behaviours of the table that are insome ways intriguing and non-obvious. Indeed, the table’sbehaviour became a talking point between G and B andtheir callers. G and B developed a local knowledge of thetable’s behaviour (its occasionally anomalous detections, itschanges in sensitivity over time) complete with ways ofinterpreting things that occurred, both expected andunexpected. Very commonly, this knowledge andinterpretations of phenomena were compared with otherviews. G (to a caller, J): “It’s interesting you’re trying togive sense to it and you do it in a different way from me.You said it was confused. I just think it is doing its thing”.

Noticing phenomena worthy of interpretation in the table’sbehaviour, offering and discussing interpretations, lookingout for things in the future, and so forth are valuableactivities for G and B in their appreciation of the Tableclothand not obstructions to its use and enjoyment. Indeed, theTablecloth seemed to offer a quite open ended set of thingsto observe even with four months of co-habitation. Anumber of phenomena occurred with requisite rarity tokeep G and B’s interest piqued. Occasionally, they wouldobserve lights pulsing on and off. Once, all the cells lit up atone end around objects placed there and, when thoseobjects were removed, a pattern of light cascaded to theother end of the table rather than gently fade at the spot.This unique occurrence “kept us talking for days”.

Illuminating Domestic ActivitiesIn the case of the History Tablecloth, such moments ofinterpretation and wonder are not problematic for foldingthe artefact into customary domestic activities. Whether itlights up or not, there’s still a table there with all its usualcapabilities. The failure of a cell to brighten or fade doesnot lead to any crisis of affordance such as pots and panscrashing to the floor. Finding the Tablecloth’s behaviourintriguing and worthy of interpretation is quite a naturalaffair to accommodate into the ordinary domestic activitiesthe table is used for: working, preparing food, eating,.

Indeed, more than that, G and B found some of theseactivities to be engagingly ‘illuminated’ (all sensesintended) by the History Tablecloth. For example, acommon routine for them just before guests arrived fordinner involved “resetting the table”, not just ‘setting’ it(G’s joke). Then, as places are marked and serving dishesplaced, a pattern unfolds before the guests’ eyes. At thesemoments the nature of that pattern, its partial coincidencewith the objects placed, how it grows, strange happenings atother meals, and so forth can be discussed. Then, when the

dishes are removed the pattern remains. It may fade or if itis ‘stuck’ it may stay for days depending on whether B or Gpress reset. Either way, there is a momento of the meal.

Some connections with everyday routines (here dining)were illuminated. Other routines were not disrupted (egusing the table for work activities). Some other activitiescame into existence where the playful opportunities of thetable were more to the fore, for example, predictingwhether a particular object would or would not be detected.In all this, that the Tablecloth’s behaviour is commonly amatter for interpretation does not majorly disrupt its use, ifanything it provides engaging opportunities for newactivities or enrichments of existing routines.

Appreciating the Tablecloth AestheticallySited as it was next to a large (old) factory window on the(now) kitchen side of B and G’s living space, the cells ofthe cloth did not appear very clearly during daylight hours.But as it grew dark, the glow from the History Tableclothbecame noticeable. G: “It’s like an electric doily. At night itreally comes into its own”. A number of B and G’s friends,who were skeptical when they first heard of ‘an electronictablecloth’ became fascinated when the table was seen firsthand and in the good viewing conditions of an autumnevening. B: “It was quite spectacular when A was sittinghere and the light came out from her. She said “it likes me’.It looks great when it’s dark”. Particular patterns might befound appealing even if the table is unresponsive. G: “I likethis pattern, it was yesterday’s dinner”. Clearly then theTablecloth has a visual aesthetic which is found appealing.

However, we would like to argue that the Tablecloth has aninteractional and interpretative aspect to its aesthetics too.That G can preserve a ‘stuck’ pattern until the next reset is afeature of the (intended and unintended) interactionalbehaviour and capability of the Tablecloth. In manyrespects, there is not so very much you can do with theTablecloth: move objects around, press reset. But, as wehave observed in previous work [7], this minimalinteractive repertoire can come to be strongly appreciated.As one does not have to continually attend to the artefactand make selections from a rich set of actions to engagewith it, there is little to learn and little to disrupt ongoingdomestic routines. Initially, B and G expected a richervisual display, “something photographic, or text perhaps, orfor activity to be recorded and replayed”. However, theminimalism of cells brightening and fading, and the simplemeans by which one interacts with the Tablecloth, came tobe preferred. G: “As I don’t have control over this, I canjust enjoy it”. Perhaps also helped by this minimalism, thetable can become an occasion for interpretation, talk andspeculation. This seemed also to be important to B and G’sappreciation of the table. B: “I like how it sometimes doesstrange things”. In this way, the sometimes anomalousbehaviour of the Tablecloth and its minimal interactivityadded to the aesthetic appeal of the piece.

CONCEPTUAL APPROPRIATION IN THE WILDIt should be clear that the field trial of the HistoryTablecloth reflected aspects of the experiences we haddesigned for, but other forms of encounter emerged as well.Most notably, the systematic ways in which theTablecloth’s behaviour diverged from the interaction wehad intended created a different experience for thevolunteers than we had expected. One of the implications ofthis was that their interpretative efforts focused onunderstanding the system’s behaviour itself, and not just theflow of objects in the home as we had intended.

What was interesting about this was the strong tendency ofour volunteers to see behaviours we perceived as erroneousas interactively rich. While we worried about the fragility ofthe load-sensing algorithm, they seemed rarely to considerthat the system might be broken, and instead entertainedvarious speculations about the complex reactions theTablecloth had to objects placed upon it. In part, this wasbecause we had never defined for them the conditions inwhich the Tablecloth should be considered as working orbroken. Instead, they were free to consider all reactions ofthe table as legitimate interactions with the weights upon it.

Under these circumstances, several conditions seemedimportant to the rich experience that our volunteers hadwith the Tablecloth. First, it clearly reacted to weightsplaced upon or taken off of it. But the occasionallyanomalous behaviour it exhibited—from failing to registervery light objects to the occasional missed placement orremoval—lent greater richness to the experience, withoutbecoming so random that subtle, emergent patterns couldnot be perceived. Indeed, it appeared that the complexity ofthe ‘erroneous’ behaviour was taken as affording a richerinteractive experience than might have been created had theTablecloth been working ‘properly’. This was possiblebecause the Tablecloth’s behaviour could be accommodatedin its setting—it was not disruptive nor destructive—andcould even engender new activities. Indeed, the actualbehaviour of the History Tablecloth led to a range ofphenomena, from those that were common and predictable,to those that were relatively uncommon but intriguing, tothose that were extremely rare and valuable as such.

In this case, the History Tablecloth exhibited a range ofsemi-reproducible, intriguing behaviours, which illuminatedthe activities of the household. It must be admitted thatmany of the phenomena we observed in use wereunanticipated and, indeed, the load sensing algorithms didnot work as intended. Ironically, this constitutes a betterdemonstration of the viability of design for interpretativeappropriation than we anticipated.

G: “I like it that it takes time to fade. If it faded instantly,it’d look far too abrupt, not gentle or abstract enough. I likeit that sometimes it gets stuck and then you can see howthings were. I’d be very self-conscious at the table if italways followed me and reacted to me. It adds interest to

what you are doing, which would not happen if thingsmoved randomly. It’s reacting but it’s doing so in a waythat gives it a life of its own. That makes it like an artwork.For a tablecloth that’s pretty good going.”

REFERENCES1. Böhlen, M. & Mateas, M. (1998). Office Plant #1.

Leonardo. Vol 31, no. 5, 345-348.

2. Carroll, J. and Kellogg, W. (1989). Artifact as theory-nexus. Proc. CHI’89.

3. Crabtree, A., Rodden, T., Hemmings, T. and Benford,S. Finding a place for UbiComp in the home. Proc.UbiComp’03.

4. Djajadiningrat, J., Gaver, W., and Frens, J. (2000).Interaction relabelling and extreme character. Proc.DIS 2000.

5. Dunne, A. (1999). Hertzian tales: Electronic products,aesthetic experience and critical design. RCACRDResearch Publications, London.

6. Gaver, W., Beaver, J., and Benford, S. (2003).Ambiguity as a resource for design. Proc. CHI’03

7. Gaver, W., Bowers, J., Boucher, A., Gellerson, H.,Pennington, S., Schmidt, A., Steed, A., Villars, N., andWalker, B. (2004). The Drift Table: Designing forludic engagement. Proc. CHI’04 Design Expo. NewYork: ACM Press.

8. Gaver, W. (2002). Designing for Homo Ludens. I3Magazine No. 12, June 2002.

9. Gaver, W., and Martin, H. (2000). Alternatives:Exploring information appliances through conceptualdesign proposals. Proc. CHI’00.

10. Huizinga, J. (1950). Homo Ludens: A study of theplay-element in culture. Boston: Beacon.

11. Kerridge, T. & A. Law. Media mediators: exploringmovement in the home. http://www.hhrc.rca.ac.uk/programmes/ra/2005/pX3.html.

12. LG Internet Fridge. www.lginternetfamily.co.uk/fridge.asp

13. Mozer, M. C. (1998). The neural network house: Anenvironment that adapts to its inhabitants. Proc. AAAISpring Symposium on Intelligent Environments, MenloPark: AAAI Press, pp. 110-114.

14. Mynatt, E., Essa, I., and Rogers, W. (2000). Increasingthe opportunities for aging in place. Proc. CUU, 65-71.

15. RCA Equator team. www.interaction.rca.ac.uk/equator/weight_furniture.html. Downloaded Dec. 2005.

16. Schmidt, A., Van Laerhoven, K., Strohbach, M.,Friday, A., and Gellersen, H. (2002) Contextacquisition based on load sensing, Proc. Ubicomp.