modeling storing and mining moving object databases

Modeling Storing and Mining Moving Object

DatabasesProceedings of the International Database Engineering and Applications Symposium

(IDEAS’04)

Sotiris BrakatsoulasDieter Pfoser

Nectaria Tryfona

Presentation byMichael J. Dudley

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

Spacial and Non-spacial Data

Both scenarios are well explored research topics

Many DBMS allow for their manipulation.

Trajectories

New field of research No commercial DBMS are available

to manage the trajectory data

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

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”

ΙΧΝΗΛΑΤΗΣ System

ΙΧΝΗΛΑΤΗΣ 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

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

PFS Core Components

The Charateriser Cluster Finder Associator

All three are used to perform data extraction on the MOD

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.

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

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)

The semantics of movement Need the moving object’s 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


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.

The semantics of movementThe 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.



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?

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


Relationships Relations between a trajectory and its

spatial environment Relations among trajectories


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

Five basic spatial relationships Stay Within Bypass Leave Enter Cross




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


Five common relations among trajectories Intersect Meet Equal Near Far


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 it’s popularity and high degree of comprehension and expressiveness.

Trajectory Class: To capture a trajectory:

Trajectory ID Vehicle ID Position

Set of Operations GetPosition GetSpeed GetTime TravelledDistance GetHeading




3D-region Class Denotes the

spatial environment of the trajectory

In this case it shows total covered area



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



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

Questions The road network of Athens, Greece


modeling storing and mining moving object databases

Documents

moving object database

moving objects position

line segments

mining process

critical rolethis point

data types

data extraction

mod use