Modeling Storing and Mining Moving Object Databases

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Modeling Storing and Mining Moving Object
Databases

• Proceedings of the International Database
  Engineering and Applications Symposium (IDEAS04)
• Sotiris Brakatsoulas
• Dieter Pfoser
• Nectaria Tryfona
• Presentation by
• Michael J. Dudley

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What is a Moving Object Database?

• A Moving Object Database (MOD) consists of
• Spatial Data
• Infrastructure information
• Roads, Buildings, Obstructions, etc
• Non-spatial Data
• Other thematic information
• Trajectories
• New area of research

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Spacial and Non-spacial Data

• Both scenarios are well explored research topics
• Many DBMS allow for their manipulation.

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Trajectories

• New field of research
• No commercial DBMS are available to manage the
  trajectory data

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Handling Trajectories

• Pre-process the data
• Deal with errors in positional measurements
• Data Modeling
• Define a conceptual model to meet systems
  requirements
• Data Storage
• Logical data models, data types and query
  processing issues

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What is a MOD use for?

• Registering current information is not enough
• A MOD must be able to extract further knowledge
  about a system
• Mini-World Fortune Teller

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????????S System

• ????????S means Path Finder in Greek
• I will use the English translation when
  discussing this system
• The Path Finder System(PFS) of Athens, Greece
• Focuses on extracting further information about
  the movement of vehicles in the Athens municipal
  area.
• Additional information about traffic conditions
• Optimal routes
• Prediction of troublesome situations

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PFS History

• PFS is a research project focusing on the
  development of a traffic management system
• Two main goals
• Registration of the semantics of moving object
  data in an object-oriented way resulting in a MOD
• Adaptation of well known and widely used mining
  functions of characterization, clustering, and
  association in the moving object application
  domain and their expression through SML, allowing
  for a formal application in MOD

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PFS Core Components

• The Charateriser
• Cluster Finder
• Associator
• All three are used to perform data extraction on
  the MOD

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Article vs. Presentation

• Article
• Section 2 Organization of the database
• Section 3 Pre-processing, modeling and storage
  issues related to trajectory data
• Section 4 Architecture and components of the
  PFS
• Section 5 Analyses the mining process and
  presents the spatial mining language
• Presentation
• I will focus on Section 2 for the remainder of
  this presentation
• Please contact me if you would like a full copy
  of this article.

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Organizing the MOD

• It is essential to study
• the movement of objects
• their properties and relations
• Fundamental concept of movements of objects
• After defining the semantics we organize them
  into a database, the MOD

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The semantics of movement

• Represent a moving object as point object
• Volume and size do not play a critical role
• This point object can be represented in a 3D
  graph
• Space (x, y)
• Time (t)

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The semantics of movement

• Need the moving objects position on a continual
  basic
• Current GPS and telecommunications technologies
  obtain position at discrete instances of time
• By interpolating these samples we can extract the
  movement of the object
• Linear interpolating takes the sample positions
  and makes them the ends points of line segments.
  The combination of the line segments makes an
  line in three-dimensional space

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The semantics of movement
The solid line below represents the movement of a
point object. Space (x- and y-axes) and time
(t-axis) are combined to form a 3D-area.
Modeling Storing and Mining Moving Object
Databases pg 3.
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The semantics of movement
The figure below shows a spatiotemporal space
(the cube in solid lines) and several
trajectories (the solid lines) contained in it.
Time moves in the upward direction, and the top
of the cube is the time of the most recent
position. The wavy-dotted lines on top symbolize
the growth of the cube with time.
Modeling Storing and Mining Moving Object
Databases pg 3.
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The semantics of movement

• In this study, the previous trajectory
  representation in three-dimensional space was
  chosen to be adequate to derive the properties
  and relationships of the object movement.
• Answers both simple and complex questions
• Which area did a vehicle cover during its trip?
• Which vehicles left Athens after midnight moving
  East and were found close to each other 2 hours
  later?

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The semantics of movement

• Properties based on requirements
• The speed of the movement
• The heading
• The direction of the vehicle
• The covered area
• Indicating the area the vehicle covered during
  its trip
• The traveled distance
• The traveled time

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The semantics of movement

• Relationships
• Relations between a trajectory and its spatial
  environment
• Relations among trajectories

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The semantics of movement

• Relations between a trajectory and its spatial
  environment (trajectory/spatial)
• Infrastructure elements
• Roads, Buildings, Parks, etc
• Imaginary entities
• City boundaries or query regions
• In a temporal context these spatial entities
  become three-dimensional represented by a 3D
  region

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The semantics of movement

• Five basic spatial relationships
• Stay Within
• Bypass
• Leave
• Enter
• Cross

Modeling Storing and Mining Moving Object
Databases pg 3.
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The semantics of movement

• Relations among trajectories (trajectory/trajector
  y)
• Additional relevant to spatial relationship
• Based on topological reasoning

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The semantics of movement

• Five common relations among trajectories
• Intersect
• Meet
• Equal
• Near
• Far

Modeling Storing and Mining Moving Object
Databases pg 3.
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The Database Schema of MOD

• Previous concepts needs to be organized to define
  the data model of MOD
• Use the class diagram of UML for the conceptual
  representation due to its popularity and high
  degree of comprehension and expressiveness.

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The Database Schema of MOD
Modeling Storing and Mining Moving Object
Databases pg 4.
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The Database Schema of MOD

• Trajectory Class
• To capture a trajectory
• Trajectory ID
• Vehicle ID
• Position
• Set of Operations
• GetPosition
• GetSpeed
• GetTime
• TravelledDistance
• GetHeading

Modeling Storing and Mining Moving Object
Databases pg 4.
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The Database Schema of MOD

• 3D-region Class
• Denotes the spatial environment of the trajectory
• In this case it shows total covered area

Modeling Storing and Mining Moving Object
Databases pg 4.
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The Database Schema of MOD

• Trajectories have one or more relations with
  other trajectories or their 3D-region class.

Modeling Storing and Mining Moving Object
Databases pg 4.
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The Database Schema of MOD

• This style of representation has the advantage of
  describing two basic concepts
• The trajectory of the moving object by keeping
  track of its movement
• The moving object by recording its last known
  position

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Questions

• The road network of Athens, Greece

Modeling Storing and Mining Moving Object
Databases pg 5.