Geographic Information SystemsGeographic Information Systems

GIS Data Databases

1 GIS Databases1 GIS Databases

A database is a shared collection of data with secure controlled access

Data are stored independently of their applications  

A GIS database contains geographic data

A DBMS is a collection of software programs that facilitates the efficient and effective storage and access of data

A GIS DBMS

2 Levels of Data Abstraction2 Levels of Data Abstraction

Conceptual data model

- user's perception of the real world

Logical data model

- a formal description of the data model   

Physical data model

- physical storage of the data (e.g., format, order, path)

Levels of Data AbstractionLevels of Data Abstraction

IncreasingAbstraction

RealityReality

Conceptual ModelConceptual Model

Logical ModelLogical Model

Physical ModelPhysical Model

Human-oriented

Computer-oriented

Real World

DatabaseSchema

Physical Model

Levels of Data Levels of Data AbstractionAbstraction

Conceptual ModelObjects and relationships

Logical Model

Diagrams And lists

Data ModelsData Models

Vector data model Raster data model

courtesy: Mary Ruvane, http://ils.unc.edu/

3 Database Functions3 Database Functions

Records, fields, and keys

- a row is a record

- a column is a field

   

3 Database Functions3 Database Functions

Map librarian and tiles

Database FunctionsDatabase Functions

Adding, updating and deleting records

Extracting information from data

Maintaining data security and integrity

Supporting applications

4 Database Data Models 4 Database Data Models (Logical Models)(Logical Models)

Hierarchical data model Network data model Relational data model Object-oriented data model

4 (3) Relational Data Model4 (3) Relational Data Model

The database consists of several two dimensional tables

A row is a record and a column is a field 

   

4 (3) Characteristics4 (3) Characteristics Every field can be used as a key in a search  A cross file search can be done by join, as long as at least

one filed is common to both files A link table can be created with needed attributes, without

actually taking storage space

4 (3) Advantages and Disadv4 (3) Advantages and Disadv Advantages

- Flexible, no structure restrictions for search

- Easy to understand

- Less data redundancy

Disadvantages

- It can be time consuming to search matching values

4 (4) Object-Oriented Data Model4 (4) Object-Oriented Data Model Objects

 Attributes  Operations

4 (4) Object-Oriented Data Model4 (4) Object-Oriented Data Model Inheritance

- Data and functions are organized in a hierarchy

- Objects inherit characteristics and functions of their ancestor objects

Animals

A head and a body, feed

Mammals

A head and a body, feed

Four legs, sit

Fish

A head and a body, feed

Fins, swim

4 (4) Object-Oriented Data Model4 (4) Object-Oriented Data Model Encapsulation

- Data and functions are combined in one object

4 (4) Object-Oriented Data Model4 (4) Object-Oriented Data Model Association and aggregation

Fish

location:time:weight:

Aquatic System

location:time:predator weight:prey biomass:temperature:

Habitat

location:time:prey biomass:temperature:

inhabitant habitat

Inhabitation

4 (4) Advantages and Disadv4 (4) Advantages and Disadv Advantages

- Easy for modeling and the representation is close to human perception

- Reduce the complexity of software development

Disadvantages

4 (4) 4 (4) Object-Relational Databases Uses an enriched set of graphic element types on top of

the three basic types of points, lines, and polygons

Object-Relational Databases Object-Relational Databases two levels of geometries: features geometry, and components of features geometry

features geometry

components

Geometry

Point Curve Surface

LineString Polygon MultiSurface

Line LinearRing

MultiCurve

MultiPolygon MultiLineString

Composed

Type

Relationship

SpatialReferenceSystem

GeometryCollection

MultiPoint

Spatial Types – OGC Simple Spatial Types – OGC Simple FeaturesFeatures

Object-Relational DatabasesObject-Relational Databases

ReadingsReadings

Chapter 3

Object-oriented (OODBMS)

- Based on OO concept to store state and behavior of GIS objects in databases

- Provide OO query tools

- Commercially not successful

Object-Relational (ORDBMS)

- Extend RDMS to handle GIS objects

- Current Geographic Databases are ORDBMS

Object-Oriented and Object-Object-Oriented and Object-Relational GIS DBMS Relational GIS DBMS

Main Types of DBMS Main Types of DBMS in GISin GIS

Relational (RDBMS) RDMS is the most popular type of DBMS

Over 95% of data in DBMS is in RDBMS DB2; SQL Server, Access; Oracle; Informix

A relational database comprises tables, a two-dimensional row, column structure. Each single table stores an object class.

Rows contain objects Columns contain object properties

or attributes Data stored in intersection of row

and column is value

1. Components of Geographic 1. Components of Geographic DataData

Conceptual model Human-oriented, conceptual description of the main

types of objects and processes relevant to a problem domain

e.g. objects/fields Logical model

Implementation oriented, but implementation-independent representation of reality; Often in the form of diagrams and lists

e.g. Raster/vector Physical model

The actual application in a GIS; describe the exact files or database tables

E.g. A shapefile is composed of a .shp file for geometry, .dbf for attributes

Feature Feature has state, behavior, and relationships with other objects

and features State: geometry and other attributes Behavior: default values, attribute domains, subtypes, split/merge policy,

relationship rules, topology rules, connectivity rules Relationships: thematic relationships and topology

Stored in feature datasets and feature classes.

Object class An object class is a regular database table in a geodatabase.

Feature class A collection of features with the same type of geometry An object class with a geometry, each row is a feature.

Feature dataset Contains feature classes sharing the same spatial reference Required for geometric network and topologies