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Location Based M-Services
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The numbers of on-line mobile personal devices
increase. New types of context-aware e-services
become possible.
Location based mobile-services
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Moving users equipped with mobile phones, PDAs,
etc., periodically disclose their positions to the service
provider
The service provider tracks the movement of the users
and provides useful services:
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“If you want to get home faster today, do not turn into street
X (where you will get into a traffic jam)”
“On the right, you should see the Smithsonian Air and Space
Museum – the museum you should definitely visit before
leaving Washington D.C.”
February 3, 2003
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LBS Architecture
Location info
Positioning
Service requests (queries)
Service provider
DBMSs
Services (location-specific,
on-time, personalized
information)
Application
Server
Locations
of users
Maps,
other info
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Role of DBMSs in LBSs
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Database Management Systems play a very
important role in such systems.
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Different types of interrelated information must
be stored and maintained in databases:
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Continuously changing positions of moving objects,
Geographic information describing roads, building,
other infrastructure,
Other non-geographic information related to
geographic objects.
New types of queries
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DBMS Research Issues in LBS
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Either these issues has been addressed in
a rather abstract and theoretical setting or
working prototypes have been developed
with rather simple functionality.
It would be interesting to take a middle
ground, and see how more interesting
(complex) LBS functionality can be
implemented on top of existing commercial
DBMS (Oracle).
February 3, 2003
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1. NN Queries in Road-Nets
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Scenarios:
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Car driver would like to find nearest hotels, or
A gas station that would like to find ten nearest cars
Such queries are called Nearest Neighbor queries
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“Nearest” must be defined in terms of a road distance
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We do not want to report a hotel or a car that is on the other
side of the river if there is no bridge nearby
To process these queries on large amounts of data
special index structures are used to index the positions
of objects queried.
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Unfortunately this approach ignores the road network
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1. NN Queries in Road-Nets
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How to process NN queries efficiently in road
networks:
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Use an index to speed up finding of a rough candidate
answer set, which is refined using the road information
Store a other type of pre-computed information about
the road network to help in search
The goal of the project would be to explore what
solution would be the most efficient, when
implemented on top of Oracle:
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How a road network should represented in a data model?
What indices should be created?
What mix of SQL, PL/SQL, Java is best suited?
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2. Continuous Queries
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Instead of just getting an answer when a query
is asked, it would be nice to get an answer that is
constantly maintained up to date as the data
changes
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The gas station would like to know continuously, which
are the ten closest cars, or
Traffic control authority would like to constantly
monitor the number of vehicles in specific areas of the
city.
Large amounts of answers to such continuous
queries may need to be maintained
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2. Continuous Queries
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On each update of the data, answers to all
continuous queries have to be reconsidered
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Queries are indexed – they become “data”, and data
updates become “queries”
How to handle large amounts of such queries?
How to handle more complex continuous queries
(e.g., nearest neighbor queries)
The goal of the project – to explore how
continuous queries on moving objects can be
most efficiently processed using Oracle.
February 3, 2003
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Contact
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Simonas Šaltenis
E1-215b
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http://www.cs.auc.dk/~simas/teaching/dat4_proposals2003.html
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[email protected]
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February 3, 2003
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