DATABASE MANAGEMENT

GI Systems and ScienceJanuary 30, 2012

Points to Cover Recap of what we covered so far A concept of database

Database Management System (DBMS) Database data models

Relational database modelObject-oriented approach

Relationship between spatial and attribute data in GIS

Data management operations in ArcGIS

Spatial Data ModelingStage of data modeling in GIS

Available options

Indentifying the spatial features form the real world that are of interest in the context of the research question

Separating real world into layers of feaures

Choosing how to represent the features

PointsLinesPolygons NetworksSurfaces

Choosing an appropriate spatial data model

Raster modelVector model

Selecting an appropriate spatial data structure to store the model within the computer

Basic raster data structureCompacted raster data structureBasic vector data structure Point dictionary structure Topological vector data structure

Spatial data

Attribute data

Data Types in GIS

Concept of Database A GIS can be described as a spatially-

enabled databaseConventional databases store attribute

dataGIS stores both attribute and spatial data

Database is a set of structured data that are related to each other in some wayOrganized filing cabinetPhone bookOn-line database of academic publications

Concept of Database Many of human activities produce data

that is stored and managed in the database environmentOur society is generating tremendous

amounts of data on daily basisData has become a valuable commodityTo realize its value, the data need to be

managed and shared efficiently

Concept of Database One of the approaches to turning data

into information is a databaseDatabase is more than just a container for

storing dataOrganize data into more meaningful and

usable formHave analytical capabilities

Concept of Database The database approach provides the

following benefitsEase of accessing data Prevention of unnecessary duplication of dataData stored independently of the application

for which they are usedSecure controlled access to dataStandards facilitate data exchangeData in the database can be shared by

different users Manual databases versus computer

databasesWhich are more effective and efficient?

Database Management System

A DBMS is a computer program that controls the storage, retrieval and modification of data in a database (Dale and McLaughlin, 1988)Comprises tools that

perform these functionsAllows users to deal

with the data without knowing much about the database itself

Figure 4.4Source: Heywood et al., 2011

Relational Database Data Model

A DBMS manages data that are organized using a database data modelSet of rules about how the objects and

relationships between them should be represented

Number of different data models used for handling attribute data in GIS

Relational data model is most used by GISThe relational data model is based on

concepts proposed by Frank Codd (1970)

Relational Database Data Model Data are organized and stored in a series of

two-dimensional tables, each of which contains records for one type of entity

Each entity has a unique identifier value assigned to itUnique identifiers allow to link (relate) data in

two or more different tablesThis structure makes possible applying queries to

one or more tables

Relational Database Data Model Types of relationships possible between entities

in a relational database

Figure 4.7Source: Heywood et al., 2011

Relational Database Data Model

Figure 4.8Source: Heywood et al., 2011

Relational Database Data Model

Querying a relational databaseQueries are built on expressions based on

relational algebra which in turn is based on Boolean logic

SQL, standard query language, has been developed to facilitate the querying of relational databasesAdvantages: completeness, simplicity,

pseudo-English language styleDisadvantages: was not developed to

handle geographical concepts such as ‘near to’, ‘far from’ or connected to

Object-Oriented Database Approach

More realistic approach to representing spatial entities in the database environmentEncapsulation: Object = State + Behaviour

State: set of values of attributes describing a spatial entity

Behaviour: methods of operating on itComposite objectHierarchy of objects

Subclass Superclass

Figure 4.17Source: Heywood et al., 2011

Object-Oriented Database Approach

Allows arranging objects into hierarchies allows differential assignment of behaviours (Inheritance)Behaviour of subclass objects = ‘own’

behaviour + ‘superclass’ behaviour Benefits of the OO approach for GIS

No differentiation between spatial and attribute data

Works better for graphic operations Disadvantage of the OO approach

Represents world as a series of rigidly bounded objects

Still under development

Data management in ArcGIS The primary data storage mechanism in

ArcGIS is the geodatabaseA collection of geographic datasets of various

types held in a common ‘container’ such as a database file or a database application

Based on an object-relational model Relations (tables) function as objects Behavior is supplied through the geodatabase

application logic implemented as a series of system tables

A key geodatabase strategy is to leverage the database management system (DBMS)Extends SQL application to feature geometry

Data management in ArcGIS Geodatabases comprise

Three primary dataset types Feature classes Raster datasets Tables

Database schema: metatables containing information about object behavior and relationships, maintaining data integrity Topologies Networks Subtypes

Source: ArcGIS 10 Help files

*

Data management in ArcGIS Types of geodatabases

File geodatabases Stored as folders in a file system. Each dataset is held as a file that can scale up to

1 TB in size. Personal geodatabases

Datasets are stored within a Microsoft Access data file

Limited in size to 2 GB ArcSDE geodatabases

Stored in a relational database using Oracle, Microsoft SQL Server, IBM DB2, IBM Informix, or PostgreSQL.

Multiuser geodatabases which are unlimited in size

Data management in ArcGIS

Figure 4.9Source: Heywood et al., 2011

Relationship between data in GIS Raster datasets

Simple raster datasets no separate attribute data table

Rater datasets with attribute tables Within a geodatabase, the raster attribute

table is saved within the raster dataset and hidden from the user

Source: ArcGIS 10 Help files *

Relationship between data in GIS Vector datasets

Data Management Operations The supported attribute column types

in the geodatabase

Source: ArcGIS 10 Help files

Data Management Operations

QueriesAttribute query

Used to find features based one particular attribute

Locational query Used to find features with locations that meet

certain conditions Works with four types of relationships: near,

adjacent to, intersect, and insideThe result of queries is a set of selected

features

Data Management Operations

JoinsAssociating two or more tables based on a

common field (key)

One-to-one relationship

One-to-many relationship