February 3, 2003 1

Location Based M-Services The numbers of on-line mobile personal devices increase. New types of

context-aware e-services become possible. Location based mobile-services

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: “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 2

LBS Architecture

Service providerDBMSs

Locationsof users

PositioningLocation info

Service requests (queries)

Services (location-specific, on-time, personalized information)

Maps,other info

ApplicationServer

February 3, 2003 3

Role of DBMSs in LBSs

Database Management Systems play a very important role in such systems. Different types of interrelated information

must be stored and maintained in databases:

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

February 3, 2003 4

DBMS Research Issues in LBS

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 5

1. NN Queries in Road-Nets

Scenarios: 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 “Nearest” must be defined in terms of a road

distance 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.

Unfortunately this approach ignores the road network

February 3, 2003 6

1. NN Queries in Road-Nets

How to process NN queries efficiently in road networks: 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: 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?

February 3, 2003 7

2. Continuous Queries

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 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

February 3, 2003 8

2. Continuous Queries

On each update of the data, answers to all continuous queries have to be reconsidered 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 9

Contact

Simonas Šaltenis E1-215b http://www.cs.auc.dk/~simas/teaching/

dat4_proposals2003.html

simas@cs.auc.dk