SOCIAL SENSING - Managing and Mining Sensor Data - page 272

tracted. The barcodes can be decoded from the photograph with the
use of barcode libraries such as ZXing [193]. At this point, the numerical
UPC value and the just-taken photograph are transferred to LiveCom-
pare 's central server. This data is stored in LiveCompare 's database for
use in future queries, and the UPC value determines the unique product
for which price comparisons are requested. The client also sends its GPS
or GSM cell information to the server so that the current store can be
identified. This location information allows LiveCompare to limit query
results to include only nearby stores. Results include store information
and the option to view the time-stamped photographs associated with
the specific product in question at each store. Users are not required
to manually input pricing data in order to improve trustworthiness; this
low burden of participation improves the ability to recruit participants
during deployment. In any participatory system, it is recognized that
to contribute data, users give up their time, attention, and mobile de-
vice's battery power. Therefore, it is critical to ensure that users have
sucient incentive to participate. LiveCompare directly addresses this
challenge through its query protocol. When a user submits a query from
agrocerystore,heidentifiestheproductforwhichhewantspricecom-
parison information by snapping a photograph of the product's price
tag (including bar code). The server appends the photograph submitted
during the query to its database . Thus, by requiring that a geotagged
photograph be uploaded as part of a query, LiveCompare automatically
populates its database whenever a user initiates a query. Thus, the
principle of increasing incentive and participation is: “ To use, you must
contribute. ”
The problem of sharing consumer prices with the use of mobile phones
has started gaining attention recently. For example, the Mobishop sys-
tem for sharing consumer prices with mobile phones has been proposed
in [146]. Methods for sharing fuel prices with the help of a network of
mobile phone cameras has been proposed in [50].
8.1.5 Location-Aware Search, Feedback, and Product Rec-
ommendation. Virtually all mobile phones have applications
which enable GPS-based searches for popular businesses such as restau-
rants, coffee shops, gas stations, or department stores. For example,
the Y ellowPages application on most mobile phones is now GPS en-
abled. Furthermore, many social review systems (which allow users to
share their opinions about businesses) such as Yelp [199] integrate the
social reviews with GPS-enabled search. This allows a user to not only
search for business of interest, but even businesses which have positive
reviews associated with them. These applications also allow users to