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Presentation on theme: "Donnie H. Kim, Kyungsik Han, Deborah Estrin UCLA CSD CENS Ubicomp 2011 EMPLOYING USER FEEDBACK FOR SEMANTIC LOCATION SERVICES."— Presentation transcript:


2 SEMANTIC LOCATION SERVICES Numerous emerging applications want colloquial places and paths rather than just coordinates E.g., personal application such as geo-reminder and location diaries Social applications such as whereabout-sharing and ride-sharing People normally think and speak locations in terms of places like my home or Eds office Location-aware applications encounter the problem of translating coordinates provided by todays position systems to semantic places

3 CHALLENGES Current location-aware applications must handle the coordinates directly Absence of a universal place database Force users to define places one-by-one by drawing circles on a map Such schemes fail in describing many interesting indoor places and poorly scale Creating indoor localization in every building is currently far-fetched Relying on users to delineate places from scratch can omit many interesting places Continuously estimating absolute positions significantly impacts battery-life on the mobile device

4 LOCI A service layer that abstracts a users location context as places and paths The service Learns new places Suggests potentially meaningful places Recognizes registered places Tracks paths connecting places Employing user feedback Managing suggested places Telling when the service detects places incorrectly

5 WHAT TO UNDERSTAND What to understand How often user feedback is needed What helps a user manage suggested places How we can encourage a user to provide feedback to the service Three-week user study with 29 participants


7 HOW TO OPERATE Initially, no places are registered with the service As the user carries around the mobile device running Loci, new places are gathered as potential everyday places waiting to be reviewed and confirmed Places are suggested when the user visits them for the first time and spends a substantial amount of time Loci automatically infers entrance to and exit from a place using Wi-Fi fingerprints Loci provides the user for recent visit times, approximate position of the place, and a list of neighboring Wi-Fi access point names as hints To assist the user in deciding if a place is valid


9 VIEW Calendar view View place visit histories in a calendar which consists of a monthly view and a daily view Map view Let a user view location trajectories of a selected day on a map List view View places by its status: registered, suggested, and blocked


11 EMBEDDED SURVEY TOOLS Place surveys To characterize places based on user feedback Users take a survey about a particular place by choosing a place from the registered place list A user selects a name category of the chosen place name, add keywords, report place-detection failures, and writes free-text comments Daily surveys To understand how often a user may need to report about failures If any discrepancies between what Loci detects and what the user remembers are noticed during a day, they are reported in the daily surveys


13 SERVICE ARCHITECTURE Place handler Detect place visits by periodically scanning neighboring Wi-Fi APs Initiate path handler as the user leaves the place Path handler Track positions using the GPS module Movement handler Find opportunities to save energy while the device is staying at a place and immobile Data storage Maintain places, visit histories, tracks, and survey answers Upload handler Triggered when the phone is plugged-in to a power outlet

14 USER STUDY RESULTS Research questions guided Loci design How often does a user need to provide feedback? What helps a user manage suggested places? How can we motivate a user to provide feedback? 29 participants Three week

15 USER FEEDBACK DEMANDS: REGISTERING NEW PLACES Average number of suggested places a user received Average number of visits per day by user

16 USER FEEDBACK DEMANDS: REPORTING PLACE FAILURES Freq.MissedDividedMergedWrong Never 845 (97.3%)793 (91.4%)844 (97.2%)850 (97.9%) Sometimes 20 (2.3%)54 (6.2%)20 (2.3%)16 (1.8%) Often 3 (0.4%)17 (1.9%)3 (0.4%)1 (0.1%) Always 0 (0%)4 (0.5%)1 (0.1%) Total 868 (100%) 176 daily surveys from 29 participants 51% of the participants submitted every day 27% reported once a day more 21% submitted none 868 place surveys from 29 participants Divided at relatively large spaces where a single Wi-Fi fingerprint couldnt cover the entire space E.g., department store, music hall Merged when a user directly moved from one place to another separated by a single floor or a hallway

17 MANAGING SUGGESTED PLACES Users usually selected either calendar view or list view to review new places Map view was used rarely Calendar view: people thought viewing place visits in a chronological order was helpful in remembering places List view: it is easier to view every suggested places in one places Map failed to provide enough information in cases where the GPS provided largely inaccurate indoor position estimation In what order they consulted the hints 42%, time map wifi 31%, map time wifi

18 ENCOURAGING USER FEEDBACK Key implication to the semantic location services People are generally open to providing feedback to improve the service Well-timed notifications and informative feedback motivates users to provide more input Post-study exit survey Mostly positive about receiving suggested places and managing personal places Maximum number of suggested places a participant will handle per day 32%, the number doesnt really matter 50%, four or above 28%, three or above Providing other contextual information about the visit or adding a social component may encourage them to engage more The most desired feature: getting reminders about new suggestions 75% thought they would register more places if Loci prompted when new places appeared 46% wanted to be prompted they were at the new place 36% preferred to be prompted when arriving at home in the evening

19 RESOURCE USAGE Energy consumption Daily average sensor on-time by participant Memory usage 0.25MB per day on average


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