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Location Information Location Information Management and Moving Object Management and Moving Object

DatabasesDatabases

““Moving Object Databases: Issues Moving Object Databases: Issues and Solutions”and Solutions”

Ouri, Bo, Sam and LiqinOuri, Bo, Sam and Liqin

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ContentsContents

Introduction Introduction Challenges of Location Information Challenges of Location Information

ManagementManagement– Location ModelingLocation Modeling– Uncertainty ManagementUncertainty Management– Distributed/Mobile EnvironmentDistributed/Mobile Environment– Location PredictionLocation Prediction

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Contents contd…Contents contd…

Moving Object DatabasesMoving Object Databases– Location ModelingLocation Modeling

» Dynamic AttributesDynamic Attributes

» Data ModelData Model

– Linguistics IssuesLinguistics Issues» Spatial and Temporal Query LanguageSpatial and Temporal Query Language

– IndexingIndexing

– Uncertainty/Imprecision ManagementUncertainty/Imprecision Management

Advantages and DisadvantagesAdvantages and Disadvantages Conclusions and Future workConclusions and Future work

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IntroductionIntroduction

Location management is managing location Location management is managing location information of mobile devices and using the information of mobile devices and using the data in various applications.data in various applications.

Location management is a fundamental Location management is a fundamental component of applications like location component of applications like location based services, tourist services, disaster based services, tourist services, disaster recovery, context awareness, and dynamic recovery, context awareness, and dynamic resource discovery.resource discovery.

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Introduction contd..Introduction contd.. Location-based services can be divided into two Location-based services can be divided into two

categories - Mobile Resource Management, and categories - Mobile Resource Management, and Location-Aware Content DeliveryLocation-Aware Content Delivery

Mobile Resource Management applicationsMobile Resource Management applications– Mobile workforce managementMobile workforce management

– Automatic location ManagementAutomatic location Management

– Transportation ManagementTransportation Management

These Systems use location data combined with route These Systems use location data combined with route schedules to track and manage service personnel or schedules to track and manage service personnel or transportation systems.transportation systems.

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Location-aware Content Delivery Location-aware Content Delivery ServicesServices

These services use location data to tailor the These services use location data to tailor the information delivered to the mobile user to information delivered to the mobile user to increase relevancy.increase relevancy.– Delivering driving directionsDelivering driving directions– Instant coupons to customers nearing a storeInstant coupons to customers nearing a store– Nearest resource information like local Nearest resource information like local

restaurants, hospitals, ATM machines, or gas restaurants, hospitals, ATM machines, or gas stationsstations

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Example queries to be answered by a Example queries to be answered by a Location Management SystemLocation Management System

Retrieve the helicopters that enter region R Retrieve the helicopters that enter region R within next 10 minutes( Future Query )within next 10 minutes( Future Query )

How many times was bus#5 late by more How many times was bus#5 late by more than 5 minutes at some station( Past Query )than 5 minutes at some station( Past Query )

Send a message when a helicopter is in a Send a message when a helicopter is in a given Region( Trigger )given Region( Trigger )

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Required Capabilities of a Required Capabilities of a Location Management SystemLocation Management System

Modeling of Location InformationModeling of Location Information Uncertainty ManagementUncertainty Management Spatio-temporal data access languagesSpatio-temporal data access languages Indexing and scalability issuesIndexing and scalability issues Data mining(traffic and location prediction)Data mining(traffic and location prediction) Privacy and SecurityPrivacy and Security Synchronization of data from multiple Synchronization of data from multiple

sensorssensors

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Location ModelingLocation Modeling

Existing DBMS are not well equipped to handle Existing DBMS are not well equipped to handle continuously changing data. Here data is continuously changing data. Here data is assumed to be constant unless explicitly assumed to be constant unless explicitly notified.notified.

To represent moving objects to the database has To represent moving objects to the database has two disadvantagestwo disadvantages– DBMS cannot handle frequent updates from many DBMS cannot handle frequent updates from many

mobile devicesmobile devices

– Frequent updates impose a serious wireless Frequent updates impose a serious wireless bandwidth overhead.bandwidth overhead.

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Using Dynamic attributes to Using Dynamic attributes to model datamodel data

This approach tries to use DBMS will new This approach tries to use DBMS will new attribute called the “dynamic attribute” to attribute called the “dynamic attribute” to model datamodel data

Dynamic attribute is used to store location as Dynamic attribute is used to store location as a function of timea function of time

The answer to a query depends on database The answer to a query depends on database contents and also the time when the query is contents and also the time when the query is asked.asked.

A higher level of abstraction is usedA higher level of abstraction is used

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Dynamic attributeDynamic attribute A Dynamic Attribute A is represented by three A Dynamic Attribute A is represented by three

sub-attributessub-attributes– A.update_valueA.update_value– A.update_timeA.update_time– A.functionA.function

The value of dynamic attribute at time The value of dynamic attribute at time A.update_time + tA.update_time + t00 is A.update_value + is A.update_value + A.function( tA.function( t00 ) )

The location attribute has sub-attributes L.x, L.y, The location attribute has sub-attributes L.x, L.y, L.speed, and L.angle or L.route, where x and y are L.speed, and L.angle or L.route, where x and y are of type Aof type A

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Example on Dynamic attributeExample on Dynamic attribute

Speed = 10miles/unit_time, Direction = NorthSpeed = 10miles/unit_time, Direction = North

update_value = 100update_value = 100 update_time = 5update_time = 5 function = 10*t for y directionfunction = 10*t for y direction

Value of y at time 15 = 100 + 10*(15-5) Value of y at time 15 = 100 + 10*(15-5) = 100+100 = 200= 100+100 = 200

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Linguistics IssuesLinguistics Issues

Traditional query languages such as SQL Traditional query languages such as SQL are inadequate for expressing queries are inadequate for expressing queries involving spatio-temporal datainvolving spatio-temporal data

Temporal predicates usedTemporal predicates used– begin_time( … )begin_time( … )– end_time( … )end_time( … )– nownow

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Spatial Query language predicatesSpatial Query language predicates

DIST( o, n ), where o and n are two mobile DIST( o, n ), where o and n are two mobile devicesdevices

INSIDE( o, R ), where o is a mobile device INSIDE( o, R ), where o is a mobile device and R is a regionand R is a region

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Queries using defined predicatesQueries using defined predicates Retrieve the pairs of objects o and n such Retrieve the pairs of objects o and n such

that the distance between o and n stays that the distance between o and n stays within 5 miles until they both enter the within 5 miles until they both enter the polynomial Ppolynomial P

RETRIEVE o, nRETRIEVE o, n FROM Moving-ObjectsFROM Moving-Objects WHERE begin_time( DIST(o,n) <=5 )<=nowWHERE begin_time( DIST(o,n) <=5 )<=now and end_time( DIST(o,n) <= 5 ) >=and end_time( DIST(o,n) <= 5 ) >= begin_time( INSIDE(o,P) ^ INSIDE(n,P))begin_time( INSIDE(o,P) ^ INSIDE(n,P))

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Other Temporal Query PredicatesOther Temporal Query Predicates

Future queriesFuture queries– UNTILUNTIL– NextTimeNextTime– Eventually_within( c, g )Eventually_within( c, g )– Eventually_after( c, g )Eventually_after( c, g )– Always_for( c, g )Always_for( c, g )

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Example Future QueryExample Future Query

“ “ Retrieve all objects o that enter the Retrieve all objects o that enter the polygon P within three units of time and polygon P within three units of time and have the attribute PRICE <= 100”have the attribute PRICE <= 100”

RETRIEVE oRETRIEVE o WHERE o.PRICE <=100 ^ WHERE o.PRICE <=100 ^

Eventually_within( 3, INSIDE(o,P) )Eventually_within( 3, INSIDE(o,P) )

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Indexing Dynamic attributesIndexing Dynamic attributes

To index queries like “Retrieve the objects To index queries like “Retrieve the objects that are currently inside the polygon P” or that are currently inside the polygon P” or “Retrieve the objects whose dynamic attribute “Retrieve the objects whose dynamic attribute value is in the range[Ac …. Ae] at time t”value is in the range[Ac …. Ae] at time t”

R+ trees cannot be used to index because they R+ trees cannot be used to index because they cannot be used to model temporal datacannot be used to model temporal data

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Indexing Contd..Indexing Contd.. Value-time space representationValue-time space representation

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Uncertainty ManagementUncertainty Management

The location of a moving object is The location of a moving object is inherently imprecise regardless the update inherently imprecise regardless the update policy.policy.

To accommodate uncertainty, a new sub-To accommodate uncertainty, a new sub-attribute to the dynamic attribute named attribute to the dynamic attribute named L.uncertainty should be added.L.uncertainty should be added.

““May” and “must” semantics should be May” and “must” semantics should be incorporated in the query languageincorporated in the query language

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Implementation DetailsImplementation Details

ArchitectureArchitecture

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Implementation Details contd..Implementation Details contd..

DBMS: Oracle database is selected as DBMS: Oracle database is selected as DBMS because it handles multi-user access DBMS because it handles multi-user access which is an inherent property.which is an inherent property.

A Wrapper application shall be used on A Wrapper application shall be used on DBMS, because normal DBMS do not have DBMS, because normal DBMS do not have spatio-temporal query handling capabilities.spatio-temporal query handling capabilities.

Because the mobile device have movement Because the mobile device have movement involved, updations to the location data is involved, updations to the location data is web enabled, a servlet is usedweb enabled, a servlet is used

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AdvantagesAdvantages

Simple approach to handle location Simple approach to handle location management using DBMS.management using DBMS.

Very few updates to database are needed.Very few updates to database are needed. The architecture shall not cost much to The architecture shall not cost much to

construct.construct. Answers queries that involve both temporal Answers queries that involve both temporal

and spatial data.and spatial data. Handles uncertainty of mobile unit location.Handles uncertainty of mobile unit location.

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DisadvantagesDisadvantages

The mobile unit should have capability to The mobile unit should have capability to give its location uncertainty.give its location uncertainty.

Dynamic attribute may also need to be Dynamic attribute may also need to be updated frequently if the mobility pattern is updated frequently if the mobility pattern is not smooth.not smooth.

A function for the dynamic attribute may A function for the dynamic attribute may not be able to expressed in few cases.not be able to expressed in few cases.

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ConclusionConclusion

Advances in wireless communication and sensor Advances in wireless communication and sensor technology are few forces that are propagating technology are few forces that are propagating computing from desktops to outdoor mobile units.computing from desktops to outdoor mobile units.

Location management is the key to applications Location management is the key to applications used by mobile units such as mobile resource used by mobile units such as mobile resource management applications and location-aware management applications and location-aware content delivery applications.content delivery applications.

Location management is key to answer queries Location management is key to answer queries that involve spatio-temporal data and answer that involve spatio-temporal data and answer issues like location modeling, uncertainity issues like location modeling, uncertainity management, and location predictionmanagement, and location prediction

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Future workFuture work

Extending the architecture of centralized Extending the architecture of centralized database to a distributed database.database to a distributed database.

Handle if uncertain data is submitted from Handle if uncertain data is submitted from different sensorsdifferent sensors

Study the implications of network QoS on Study the implications of network QoS on update policies and query processing.update policies and query processing.

Integrate with GISIntegrate with GIS