Research Overview Kyriakos Mouratidis Assistant Professor School of Information Systems Singapore Management University http://www.mysmu.edu/faculty/k yriakos/
Dec 27, 2015
Research Overview
Kyriakos Mouratidis
Assistant Professor
School of Information Systems
Singapore Management University
http://www.mysmu.edu/faculty/kyriakos/
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Spatial Queries
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- Indexing spatial data and query processingE.g., “find the 10 closest restaurants to my location”
- K nearest neighbors (if K=2)
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Continuous Queries
Continuous re-evaluation as data change. Eg:• “monitor who are the 10 SMU students that are
closest to my location as I walk around”
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Continuous Queries• Cont. NN in Euclidean space: SIGMOD’05• Cont. NN in road networks: VLDB’06• Cont. Top-k monitoring: SIGMOD’06
– Eg: "continuously report the 5 most interesting stocks according to my investment criteria”
• Cont. Text queries on document streams: TKDE’11
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Monitoring Server
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Top-k2 docs
Sliding Window
Incoming Document Stream
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Spatial Optimization Queries
• E.g.: At which 10 positions in S’pore should McDonalds open branches so that the average distance between clients and their closest branch is minimized?
• E.g.: Given a coverage radius and a maximum capacity of a Mobile Service Provider’s base stations, find a (dynamic) assignment of mobile phone users to a base station so that the average distance between them is minimal.
Spatial Optimization Example
• A set of wireless routers serve a set of laptops– each router can serve at most 3 laptops concurrently– the signal strength (ie, the QoS) drops with distance
• How can we assign laptops to routers so that we1. Serve the maximum possible number of users, AND2. Minimize the average distance between laptops-routers?
• Assignments by “local” criteria (eg, NN below) would fail!
3-Nearest Neighbor Queries
Spatial Optimization Example
• Optimal Assignment:
• Aim: quickly compute the optimal assignment over large datasets [SIGMOD’08, TODS’10]
Location Privacy
• How could an untrusted server answer your spatial queries without learning your location?
• Example: shortest path query [VLDB’12]
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Destination
Source
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Building block: Hardware-aided PIR
• Practical PIR = hardware-aided PIR[Williams & Sion: Usable PIR. NDSS’08]
DatabaseClient
Page requests
Data pages
SCP
LBS
SSL connection
Fetching a disk page: amortized comp. cost O(log2N)i.e., approx. 1 sec for a Gigabyte database
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Verification in Outsourced Databases:
• Model: Database as a Service
• Data Owner uploads DB to untrusted server
• Server hosts the DB and answers queries from users
• How can users verify that the results to their queries are authentic and complete?
• Examples: text queries [VLDB’08], relational/spatial queries [VLDBJ’09], shortest path queries [ICDE’10]…
Other cool stuff
• TripAdvisor has hotel information, such as: price, value, location, cleanliness, user rating
• Imagine this interface to select top-10 options:
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Immutable Regions [VLDB’13]