Problem

1. On Monitoring the top-k Unsafe PlacesPresented by: Ling HuCollege of Computer and Information ScienceNortheastern University, Boston, MA 02115audnyhu@ccs.neu.edu We continuously monitor the most unsafe places in a city …… • Problem • Police units patrol around and protect neighborhoods, how to efficiently find out places that are under-protected? • Continuous Top-k Unsafe Places (CTUP) query is to continuously monitor the k places with the smallest safeties (the difference between actual protection and required protection of the places). • Solutions • Basic Continuous Top-k Unsafe Places (BasicCTUP) • Experiments • Initialization Cost • Contributions • CTUP query is a novel addition to the family of continuous location-based queries. Solving this query may have a strong impact on the society. • It proposed two solutions to the CTUP query and an optimization to maintain the lower bounds of cells. • It evaluated the proposed schemes and revealed some insights on how to choose certain system parameters. • Update Cost • Drawbacks of BasicCTUP • Unnecessary lower bound decreasing • Too many places maintained in memory • Flashing cells increase cost • Optimized Continuous Top-k Unsafe Places (OptCTUP) • List of units decreased cell’s lower bound for each cell (DOO) • Maintain a small number of places (safety ≤SK+△) • All cells are dark, no flashing phenomenon • Model • A centralized server stores the map of the city, along with the required protection of every place in the city. • All police units report their position updates to the server. • The server gives up-to-date top-k unsafe places. • Effect of DOO optimization • Decrease Once Optimization (DOO) • For more information: • http://www.ccs.neu.edu/research/dblab • Prof. Donghui Zhang – donghui@ccs.neu.edu • Yang Du – duy@ccs.neu.edu • Ling Hu – audnyhu@ccs.neu.edu