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Prototypes and Paratypes:

Designing Mobile andUbiquitous ComputingApplications

Conducting user-centered design is aprimary challenge in ubiquitous com-puting.1 Ubiquitous computing appli-cations are exploratory by nature,and often users are unfamiliar with

their interaction paradigms and features. Further-more, these technologies can disrupt existing social

practices, potentially weakeningor invalidating evaluation results.So, when designing these appli-cations, realistic testing environ-ments are essential. However,high development costs andusers’ unfamiliarity with thetechnology make it costly toapply quantitative analytic meth-ods, such as controlled perfor-mance measurements, or quali-

tative techniques, such as iterative field testing.Over the past several years, members of our

research group have been designing and evaluat-ing several mobile and ubiquitous computingapplications including memory aids, messagingapplications, and technologies that help educatechildren with special needs. To tackle the uniquedesign and evaluation challenges of these appli-cations, we’ve refined design and prototypingtechniques to be more appropriate for the ubiq-uitous computing domain.

Prototyping techniques have traditionally sup-ported artifact design, and developers typically

view prototypes as a physical prop of an intendeddesign. However, prototypes more generally canreplicate various aspects of an artifact before thefinal product is built by reproducing the physi-cal, computational, or experiential properties ofits design.2 Two kinds of prototyping techniquescan be particularly effective for developing mobileand ubiquitous computing applications: com-pound prototypes and situated experience pro-totypes. Compound prototypes combine the finalproduct’s user interface (UI) with a computationalimplementation that runs on a separate systemwithout the resource constraints of the targetdevice. This model lets researchers and designersevaluate a new application’s physicality and aes-thetics as well as its functionality. Situated expe-rience prototypes, or paratypes, include experi-mental protocols that attempt to reproduce userinteraction with the system in real situations, andcan optionally use common prototyping instru-ments such as paper mock-ups or physical props.

Using our Personal Audio Loop (PAL) projectas a case study, we discuss how you can fruitfullyemploy compound prototypes and paratypeswhen designing and developing mobile and ubiq-uitous computing applications.

PAL: Personal Audio LoopPAL is a portable audio memory aid motivated

by the everyday experience of conversationalbreakdowns, as people try to remember some-

Combining physical, contextual, and functional prototyping techniquesto generate compound prototypes and situated experience prototypes, orparatypes, can be particularly useful for mobile and ubiquitouscomputing applications.

R A P I D P R O T O T Y P I N G

Gregory D. Abowd, Gillian R.Hayes, Giovanni Iachello, Julie A.Kientz, Shwetak N. Patel, andMolly M. StevensGeorgia Institute of Technology

Khai N. TruongUniversity of Toronto

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thing they recently said or heard.3 Exam-ples include the topic of a conversationbefore an interruption, or a name ornumber briefly heard in situations ofhigh cognitive load like a party or con-ference. The initial concept was to letsomeone replay easily, at any moment intime, sounds heard in the recent past upto a defined maximum time span (forexample, up to one hour). Figure 1shows an implementation concept ofPAL on a cell phone.

PAL’s design process shows how weused compound prototypes and paratypesfor a novel application that would havebeen difficult to design with more tradi-tional user-centered practices. Most peo-ple haven’t experienced an automatic,audio-based memory aid, so they wouldhave little context to leverage in under-standing its design. Therefore, to answerquestions about PAL, user study partici-pants had to understand its capabilitiesand be able to refer to concrete momentswhen they could have used it. The ques-tions covered three important issues:

• Usability: How should the applica-tion deliver functionality to maxi-mize its effectiveness and minimizeits distraction?

• Usefulness: How often and in whatsituations do people recognize a needfor near-term, audio-memory aid and

think they would actually use the tool?• Acceptance: What social and legal

concerns might prevent the successfuldeployment of an application thatcontinuously records?

When we started analyzing thesequestions, we had developed PAL pro-totypes on PCs and PDAs, but we didn’thave a robust enough prototype on theform factor we had chosen, a mobilephone, to give to users. At the same time,we didn’t want to commit additionaldevelopment resources before gainingfurther insight into these issues—a com-mon concern when developing mobileand ubiquitous computing applications.Thus, to study these issues without arobust implementation, we used com-pound prototypes and paratypes.

Compound prototypesCompound prototypes are representa-

tive artifacts that combine a design’s phys-ical and computational nature by pro-viding a realistic UI that controls a faithfulimplementation of the application onanother computing system. Compoundprototypes have helped IT productdevelopment—for example, developersworking on a digital camera for Kodakattached a physical prop of the camera,which provided the UI, to a PC, whichprovided the application’s computing

capabilities.4 Similarly, in the 1970s, HCIresearch on desktop systems greatly ben-efited from having access to machines thatwere five to 10 years more advanced thanwhat was widely available. When thetechnology became commercially viable,the desktop interface was ready for rapidadoption. Compound prototypes letdesigners test sophisticated applicationson real, sometimes limited, devices whileavoiding development risks and commit-ments to lengthy debugging and opti-mization on these platforms.

The PAL usability studyTo understand whether we could use

a mobile phone as the PAL interface, webuilt a compound prototype using thephone as the interface to the applicationcore running on a PC. This let us con-duct a controlled usability study prior todeveloping a fully functioning version ofPAL on a mobile phone.

The limited performance and interfaceof the selected platform (the MotorolaiDEN i730, a clamshell, Java-enabledphone) raised concerns about PAL’susability. When closed, the phone offersonly three buttons for input, a 150 � 10pixel graphical monochrome display,and an LED that lights to one of threecolors (green, red, and blue). The com-pound prototype we used for this studyconsisted of a phone connected via ser-ial cable to a laptop (see figure 2). A Javaprogram on the phone transmitted but-ton presses to the PC and provided dis-play feedback. Software on the PCimplemented the application core,including audio capture, recording, andplayback.

PAL’s intended use involves replayingconversations during which the user waspresent. We used the compound proto-

Backward/forwardnavigation

Playback/recordtoggle

Mode

Mode light

Microphone

Earmark

Playback position

Figure 1. The Personal Audio Loop, whichcan be attached to a belt clip (inset), hasthree buttons that control navigationwithin the recording and record/playbackmode. A timeline indicates the currentmode and relative place in the buffer.

type in a controlled study designed tomimic this scenario and based on ascripted dialog of approximately fiveminutes. In this script, the participantasked the researcher predetermined ques-tions, and the researcher replied withscripted answers. Answers purposelyinvolved numerous details to increase thelikelihood that participants couldn’trecall everything from memory. Aftercompleting the script, the researcherasked the participant about the scriptedreplies, inviting the participant to use PALif he or she didn’t recall the answer. Theresearchers encouraged subjects to thinkaloud while using the prototype.

Eighteen students and faculty from ourinstitution (five female and 13 male, rang-ing in age from 18 to 50) participated inthe study. Being HCI practitioners, theyprovided expert feedback on commondesign heuristics. All participants navi-gated the audio well enough to completeall tasks. They commented that the devicewas easy to use with one hand and smallenough to carry at all times. They alsocould clearly understand the audio even inits highly compressed form. The studyresults confirmed the interface’s effec-tiveness for its intended purpose and pro-vided several insights that we incorpo-rated into the new design. Significantly,some issues dealt with functionality, suchas participants expressing the desire forbookmarks in the recording, and somefocused on physical interaction with thedevice, such as mapping forward andreverse buttons to functions.

Compound prototypes in practiceBy using a fully functional and physi-

cally realistic prototype, designers canprobe the application’s look and feel(physical prototype) and functionality(computational prototype) and excludesome elements of interface usability aspotential causes for failure in subsequentfield trials. While studying technologieswith potentially complex social ramifi-

cations, like PAL, it’s especially impor-tant to clearly understand and attributepotential adoption patterns. Thus, byevaluating usability and functionalityaspects, we were able to target the appli-cation’s more experiential aspects in real-world settings in subsequent studies.

Our experience with PAL suggests thatcompound prototypes are quite useful inprototyping and evaluating ubiquitouscomputing applications designed for plat-forms with limited resources. Compoundprototypes have been used in engineer-ing and industrial design for years, andwe find them particularly appropriate foruser-centered development on mobilephones—an important platform forubiquitous computing. Compelling rea-sons exist for making the compound pro-totyping of phone-based applicationsmore viable. For example, researcherscould create prototyping toolkits to facil-itate development, testing, and portingof compound prototypes to a range ofdifferent devices. These toolkits wouldnot only facilitate usability testing butalso enable the comparison of alternativeform factors and UI paradigms with thesame application core.

ParatypesMarion Buchenau and Jane Fulton

Suri show, with their concept of experi-ence prototypes, that designers can use aprototype for gathering feedback on theexperience involved in using a certaindesign—role-playing a train journey, forexample.4 Extending this concept, situ-ated experience prototypes let researchersand designers observe user experiencesby simulating a technology’s potential usein real-life situations—not in a lab or inrole-playing. In this sense, we define situ-ated experience prototypes as paratypes:models (“-types”) of interaction experi-ences that happen alongside (“para-”)real, experienced situations.

Paratypes are different from typicalexperience prototypes in that the latter

creates exemplary experiences, and theformer leverages real life to test a designconcept—only the instance of the tech-nology’s use is simulated or imagined.By creating an instance of use embed-ded in real life, you can gather moreauthentic reactions from participants.These procedures can yield more accu-rate conclusions than designers canreach using participative storyboardsor scenarios, which investigate partici-pants’ thoughts about a technologyexemplified in a narrative account.

We used paratypes for two PAL userstudies: a diary study and a proxy study.

The PAL diary studyTo probe PAL’s potential usefulness,

the diary study aimed to understand,where, why, and how often participantswould use the application. After partici-pants interacted with a fully working ver-sion of PAL to understand its functions,we used diaries as a paratype—that is, areporting tool for potential PAL uses.

Paratypes are especially useful whenyou can’t or don’t want to use the actualapplication for field testing. In this study,we used the diary because the PAL pro-totype wasn’t robust enough to withstanduser deployment. We didn’t want to com-mit additional resources to product hard-ening and deployment maintenance (forexample, replacing defective phones andresponding to emergent problems) beforehaving a strong argument in favor ofPAL’s utility and acceptability.

Developers have used diary studies asinquiry tools in the mobile technologydesign process—for example, allowing

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Figure 2. The compound prototype used in the usability study. The phone provides theuser interface, while the core application runs on the laptop.

participants to take notes about theirdaily activities.5 Diaries can functionwell as paratypes as a documentationtool for recording the reflections of par-ticipants in simulated interaction. In thiscase, the diary exercise’s focus is docu-menting imagined uses of technology,not participants’ activities. Again, it’simportant to balance the ecologicalvalidity of gathering user data in situagainst the interruption of everydayactivity flow that recording personalobservations causes.

This use of paratypes is somewhatsimilar to experience sampling methodtools, in which a digital device interruptsthe participant, prompting him or herto respond to questions or partake insimulated interaction.6 However, withparatypes, use is initiated by the partic-ipants, not the artifact, and thus can bemore salient. Of course, this means theremust be a reasonable expectation thatthe participants will be sufficiently moti-vated to initiate the survey at appropri-ate times.

In our case study, diaries let us probequestions about application usefulness ina situated setting. PAL is characterizedby isolated and intentional interaction.Hence, the PAL diary entries focused onevents, discrete instances of imagined usethat participants can recall during in-depth interviews even at a distance of afew days.

Twelve experienced mobile phone users(five female, seven male, ages 22 to 60)participated in the study. We intention-

ally included these users to gain opinionsfrom people representative of medium-to-advanced cell-phone users in the USmarket. Participants included a psychol-ogist, finance manager, realtor, car dealer,consultant, professor, and homemaker.

To ensure that participants understoodPAL’s functionality, we demonstrated afully working version of the device andlet them use it until they were comfort-able with it. Then, we asked participantsto carry pocket-sized diaries (sized sim-ilarly to the phones) and to record oneentry for each time they would haveneeded or liked to use the PAL applica-tion. Each diary page contained a formabout each potential use instance (see fig-ure 3). Participants described the contentof the audio to retrieve, when and wherethe event occurred, and whether any peo-ple unrelated to the conversation werenearby. Participants also estimated howfar in the past the salient audio contentwas and rated how problematic it was toforget that information. The diarieshelped us understand the potential usesas well as the difficulties encountered bycarrying this pocket-sized device at alltimes and interacting with it when needed.

The participants in the PAL diarystudy carried the diaries for up to threeweeks. At the end of each week, we col-lected the diaries and conducted semi-structured interviews to examine indetail some of the diary entries. Weinquired about their perceptions of thesocial appropriateness of using the appli-cation in terms of the specific context,

privacy, and the disruption inherent ininteracting with the device in front ofothers. We then gave a fresh diary toeach participant who chose to continue.

We collected data on more than 100events. We gathered both quantitativeand qualitative data by following up on83 of those events during the interviews.Quantitative data included statistics suchas the average number of reported eventsper week and how long in the past theaudio mentioned the event that wasreferred to. The diaries let us transitionfrom quantitative inquiry to subjective,qualitative questions without sacrificingfirm experiential grounding. For exam-ple, after the second and third weeks ofuse, we asked participants subjectivequestions about their reactions to hypo-thetical situations in which a conversa-tion partner objects to their use of theapplication. In most cases, participantsstated that such an objection would “not[be] likely” and indicated that they wouldnot have complied with the objection,had there been one, in roughly two-thirdsof the queried events. (This data is hypo-thetical in nature and should be consid-ered with caution.)

At this point, we were able to askquestions that required a good under-standing of how, when, and where peo-ple would use the application. For exam-ple, we asked how far away they wouldlike PAL to record (67 percent chose“within a small room”). These data ledus to the third acceptance study tounderstand how conversation partnerswould feel about PAL.

Participants’ comments in the diarystudy left open the question of how theirconversation partners might react, know-ing that PAL was being used in their pres-ence. A long-term deployment mighthave provided answers to these ques-tions. So, we started testing the final

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Figure 3. Participants kept personaldiaries roughly the size of the phone andrecorded an entry each time they wouldhave used the PAL application.

product in a small deployment. Eventu-ally, most participants stopped usingPAL, regularly reporting that robustnessproblems (mainly phone OS crashes, duein part to the high processor load thatPAL caused) and availability issues (fastdrain on the battery, that, again, PALcaused) generated more discomfort thanthe application was worth. Unable todirectly examine PAL’s social issues, wedesigned a new study to understand theacceptance issues PAL engendered with-out the need of a deployment.

The PAL human proxy studyIn the second study, the human proxy

study, we tackled acceptance questionsrelated to the burden imposed on con-versation partners’ privacy and the socialappropriateness of using the application,both from a relational viewpoint andwith regards to disrupting interpersonalinteraction. We surveyed the PAL user’sconversation partners, asking:

• Do you object to people using a devicethat could potentially record you? Ifso, why? Do your objections dependon location, topic, and perceived con-fidentiality? (These questions were rel-evant in the light of context-sensingtechnologies that could be imple-mented on the phone.)

• What parameters, such as retentiontime, should change to compromisebetween your interests and those ofyour conversation partners?

This study relied on human proxies—that is, individuals who introduced a sim-ulated PAL in real-life situations and thenprobed their conversation partners’ reac-tions by using a simple survey adminis-tered on the fly on the researchers’ behalf.This experimental design, as opposed toa traditional survey, let us address thecommon phenomenon in which people’s

stated opinions and preferences on pri-vacy are often different from their every-day social behavior.7 We chose not tohave proxies actually use PAL on ethicalgrounds and to avoid potentially con-tentious situations, even if the applica-tion was at the time fit for use by a smallgroup of researchers who could havecoped with occasional malfunctions.Using a paratype rather than a fully func-tioning device let us capture participants’reactions in real social situations, with-out the potentially disruptive effects ofintroducing the actual device.

In this study, human proxies simulatedthe application’s use with the people theywould encounter during their normaldaily activities and collected their reac-tions on the researchers’ behalf. As theproxies conducted their activities, theyasked adults they encountered (acquain-tances as well as unknowns), with whomthey would have a conversation, to reada description of PAL and fill out a surveyabout the application. The survey askedparticipants to suppose that the proxyhad been using PAL and to provide theiropinions about it. The proxies carried aworking PAL prototype that wasn’tactive at the time but could be activated

to show participants its functionality.In this sense, the survey instrument and

the human proxy constitute a paratype:Together they create a simulated use ofPAL in real-life situations without theneed of an actual device. The paratype inthis case again provides imminent refer-ence to the situation. In the survey, weprobed the situation’s salient elements,including its place, the people who tookpart in it, and the activity the conversa-tion was achieving, as determinant ele-ments of the person’s behavior (similar tothe characterization of situation proposedby social scientists like Erving Goffman8).

The survey was anonymous and com-prised two parts linked by a unique num-ber (see figure 4). The proxy filled outthe left part with information about theconversation’s place, topic, and envi-ronment. The participant received theright part, which was designed to be self-explanatory and consisted of a descrip-tion of PAL and the survey on a return-addressed postcard. We coded the backof both parts with numbers that later letus associate the returned postcard to theproxy’s portion of the survey.

When possible, the proxy explainedthe survey to the participant and showed

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Figure 4. The proxy survey comprisedtwo parts: one the proxy filled out (left)and the other the participant filled out.

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the working PAL application on request.The proxy asked the participant to fillout the survey, preferably immediately,to preserve recall accuracy. Otherwise,the participant could mail back the sur-vey card at his or her convenience. Tocontrol recall accuracy, we asked partic-ipants to indicate the date they completedthe survey; the proxy also recorded whenthe survey was distributed.

Administering this kind of survey wasrelatively unproblematic for the proxies.The cards were portable, preaddressed,and perforated. Of 45 distributed surveys,we received 41 responses. Most surveyswere completed on the spot, and ninewere mailed back to us. Only one indi-vidual refused to accept a survey fromus. The high response rate, both fromacquaintances of the proxies and frompeople whom they had just met, suggeststhat the social relationship originatingthrough a conversation, however brief,was sufficient to encourage most partici-pants to complete and return the surveys.An essential feature of this survey was itsbrevity, to minimize its impact on con-versational routines. The survey focusedon a single interaction instance involvingthe device, thus preserving situationalvalidity and participant understanding ofthe usage context and social environment.

Paratypes in practiceA fundamental requirement for a suc-

cessful paratype is that participants under-stand the application’s functionality. Inthe diary study, we achieved this bydemonstrating the working prototype toparticipants to help them gain immediateand tangible understanding of how theapplication worked, ensuring that thediary responses would be relevant. Addi-tionally, it communicated to the partici-pants that the application was feasible.Participants reported that after thedemonstration, they were more interestedin the project, which we believe increaseddiary response rate and quality.

In the proxy study, the survey was self-contained, which allowed the proxy togive it to the participant with little expla-nation if the situation didn’t allow for amore prolonged interaction, such as ata supermarket check-out. The descrip-tion and picture on the survey providedsufficient information about the appli-cation (we conducted a preparatorystudy to verify this). In fact, one-third ofthe participants provided comments andopinions on the backs of the cards, sug-gesting that the application concept andthe paratype’s immediacy engaged them.

Because paratypes are administeredalongside everyday situations, it’s essen-tial that they be fit for use in the partic-ipant’s social and physical environment.Paratypes must be

• Unobtrusive. Researchers must mini-mize time dealing with any survey toolby gathering only essential informationand perhaps using Likert scales or checkboxes instead of free-form questions.

• Compatible with the participant’sexpected cognitive load in the use sit-uation. You can achieve this by usingplain language and a simple sentencestructure and offering clear, step-by-step instructions on using the paratype.

• Compatible with the physical envi-ronment. For example, if some userscan’t fill out a questionnaire, let themdefer it to a more convenient time andplace. You should provide any addi-tional material needed to use theparatype (for example, writing imple-ments and demonstrative objects).

Gathering participants’ consent can bethe largest hurdle. First, in a rushed sit-uation, participants might not be able tofully understand or consent to partici-pating. Second, recording that consentcan be complicated in the context of theexperience. Researchers might need tofind ways to minimize their impact ifstudy participants can’t be enrolled

before using the paratype. In our study,when researchers couldn’t obtain verbalconsent, they gave the consent form tothe participant along with the survey tobe mailed back to the researchers.

Paratypes can’t easily integrate withWizard of Oz prototyping schemes,which try to capture the experience ofusing an artifact by intelligently simu-lating its behavior. However, Wizard ofOz techniques are often more amenableto laboratory-produced or, if in thefield, fabricated situations. For example,Yang Li and his colleagues report on Li’sTopiary system for producing Wizard ofOz prototypes of location-enhancedapplications tested in the field.9 Theirevaluation employs tasks created for thetest. Instead, paratypes share the conceptof “situatedness” with cultural probes.10

They study interaction instances thatrefer to the everyday life situations theparticipants experience (similar to howcultural probes help reflect on everydayuse artifacts). In this way, designersexpectedly gain more accurate and rele-vant feedback.

Experience with compound pro-totypes and paratypes not onlyhas let us revise and develop newversions of PAL but also has pro-

vided us insight into social and privacyaspects of this applications class. Futureresearch into and applications of thesetechniques will focus on settings in whichother techniques might be too intrusiveor might not yield useful results, such ashealthcare and home environments.Applying these techniques successfullywill require careful prototype design withan emphasis on creating close approxi-mations to the technologies in situ withminimal intrusion on the user.

ACKNOWLEDGMENTSNational Science Foundation Information Technol-ogy Research grant 0121661, the NSF GraduateResearch Fellowship Program, the MacArthur Foun-

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dation, and Intel partly supported this work. Thanksto Elaine Huang, Kris Nagel, Delphine Nain, and JaySummet for their thoughtful comments. Thanks toMotorola, and specifically Joe Dvorak of the iDENgroup, for supplying the i730 handsets we used forthese studies. Human subjects research conductedfor this article is covered under Institutional ReviewBoard approved protocols H03221, H03217, andH04153 at the Georgia Institute of Technology.

REFERENCES1. G.D. Abowd and E.D. Mynatt, “Charting

Past, Present and Future Research in Ubiq-uitous Computing,” ACM Trans. Com-puter-Human Interaction, vol. 7, no. 1,2000, pp. 29–58.

2. S. Houde and C. Hill, “What Do PrototypesPrototype?” Handbook of Human-Com-puter Interaction (2nd ed.), M. Helander,T. Landauer, and P. Prabhu, ed., Elsevier Sci-ence, 1997.

3. G.R. Hayes et al., “The Personal AudioLoop: Designing a Ubiquitous Audio-BasedMemory Aid,” Proc. 6th Int’l Conf. HumanComputer Interaction with Mobile Devicesand Services (Mobile HCI 04), LNCS 3160,Springer, 2004, pp. 168–179.

4. M. Buchenau and J.F. Suri, “ExperiencePrototyping,” Proc. Conf. Designing Inter-active Systems (DIS 00), ACM Press, 2000,pp. 424–433.

5. M. Czerwinski, E. Horvitz, and S. Wilhite,“A Diary Study of Task Switching andInterruptions,” Proc. Conf. Human Factorsin Computing Systems (CHI 04), ACMPress, 2004, pp. 175–182.

6. R. Larson and M. Csikszentmihalyi, “TheExperience Sampling Method,” New Direc-tions for Methodology of Social and Behav-ioral Science, vol. 15, 1983, pp. 41–56.

7. M. Ackerman, L. Cranor, and J. Reagle, “Pri-vacy in E-Commerce: Examining User Sce-narios and Privacy Preferences,” Proc. E-Commerce 99, ACM Press, 1999, pp. 1–8.

8. E. Goffman, Behavior In Public Places, FreePress, 1966.

9. Y. Li, J. Hong, and J. Landay, “Topiary: ATool for Prototyping Location-EnhancedApplications,” Proc. 17th Annual ACMSymp. User Interface Software and Tech-nology (UIST 04), ACM Press, 2004, pp.217–226.

10. B. Gaver, T. Dunne, and E. Pacenti, “Cul-tural Probes,” Interactions: New Visions ofHuman-Computer Interaction, vol. 6, no.1, 1999, pp. 21–29.

the AUTHORS

Gregory D. Abowd is an associate professor in the College of Computing and GVU Cen-ter at the Georgia Institute of Technology and director of the Aware Home Research Ini-tiative. His research focuses on an application-driven approach to ubiquitous computingconcerning both HCI and software engineering issues. He received a DPhil in computa-tion from the University of Oxford. He’s a member of the IEEE Computer Society and theACM. Contact him at GVU Center, Georgia Inst. of Technology, Technology SquareResearch Bldg., 85 5th St., N.W., Atlanta, GA 30332-0760; abowd@cc.gatech.edu;www.gregoryabowd.com.

Gillian R. Hayes is a PhD candidate in the College of Computing and GVU Centerat the Georgia Institute of Technology. Her research focuses on enabling capture ofrich data in informal and unstructured settings and allowing access to that data. Shereceived her BS in computer science and mathematics from Vanderbilt University.She’s a member of the IEEE Computer Society and the ACM. Contact her at GVUCenter, Georgia Inst. of Technology, Technology Square Research Bldg., 85 5th St.,N.W., Atlanta, GA 30332-0760; gillian@cc.gatech.edu; www.gillianhayes.com.

Giovanni Iachello is a PhD candidate in the College of Computing and GVU Centerat the Georgia Institute of Technology. His research focuses on information securityin connection to ubiquitous computing applications and social and policy issues. Hereceived a Laurea degree in informatics engineering from Padua University. He’s amember of the ACM, the IEEE, and IFIP WG9.6/11.7 IT Misuse and the Law. Contacthim at GVU Center, Georgia Inst. of Technology, Technology Square Research Bldg.,85 5th St., N.W., Atlanta, GA 30332-0760; giac@cc.gatech.edu; www.cc.gatech.edu/~giac.

Julie A. Kientz is a PhD student in the College of Computing and GVU Center atthe Georgia Institute of Technology. Her research focuses on collaborative access toindividual experiences. She received her BS in computer science and engineeringfrom the University of Toledo. She’s a member of the IEEE Computer Society and theACM. Contact her at GVU Center, Georgia Inst. of Technology, Technology SquareResearch Bldg., 85 5th St., N.W., Atlanta, GA 30332-0760; julie@cc.gatech.edu;www.cc.gatech.edu/~julie.

Shwetak N. Patel is a PhD student in the College of Computing and GVU Center atthe Georgia Institute of Technology. His research focuses on context-aware mobilephone interaction techniques and applications. He received his BS in computer sci-ence from the Georgia Institute of Technology. He’s a member of the IEEE ComputerSociety and the ACM. Contact him at GVU Center, Georgia Inst. of Technology,Technology Square Research Bldg., 85 5th St., N.W., Atlanta, GA 30332-0760;shwetak@cc.gatech.edu; www.cc.gatech.edu/~shwetak.

Molly M. Stevens is a research scientist at the Aware Home Research Initiative at theGeorgia Institute of Technology. Her research interests include collecting, archiving,annotating, and retrieving artifacts related to family memories. Most recently her focushas been on the boundaries of low and high tech in the scrapbooking hobby. Contacther at 20 Randolph Place, West Orange, NJ 07052; mollystevens@mindspring.com;www.mollystevens.com.

Khai N. Truong is an assistant professor in the Department of Computer Science at theUniversity of Toronto. His research focuses on automating the capture of experiencesand providing access to them. He received his PhD in computer science from the Geor-gia Institute of Technology. Contact him at Sandford Fleming Bldg., 10 King's CollegeRd. Room 3302, Toronto, ON M5S 3G4; khai@cs.toronto.edu; www.khaitruong.com.