1. Geographic Information Systems
GIS Data Databases

2. 1 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

3. 2 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)

4. Levels of Data Abstraction
Human-oriented
Reality
Conceptual Model
Increasing
Abstraction
Logical Model
Computer-oriented
Physical Model

5. Levels of Data Abstraction
Conceptual Model
Objects and relationships
Real World
Logical Model
Diagrams
And lists
Physical Model
Database
Schema

6. Data Models Vector data model Raster data model
courtesy: Mary Ruvane,

7. 3 Database Functions Records, fields, and keys - a row is a record
- a column is a field
   

8. 3 Database Functions
Map librarian and tiles

9. Database Functions Adding, updating and deleting records
Extracting information from data
Maintaining data security and integrity
Supporting applications

10. 4 Database Data Models (Logical Models)
Hierarchical data model
Network data model
Relational data model
Object-oriented data model

12. 4 (3) Relational Data Model
The database consists of several two dimensional tables
A row is a record and a column is a field 
   

13. 4 (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

14. 4 (3) Advantages and Disadv
- Flexible, no structure restrictions for search
- Easy to understand
- Less data redundancy
Disadvantages
- It can be time consuming to search matching values

15. 4 (4) Object-Oriented Data Model
Objects
 Attributes
 Operations

16. 4 (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

17. 4 (4) Object-Oriented Data Model
Encapsulation
- Data and functions are combined in one object

18. 4 (4) Object-Oriented Data Model
Association and aggregation
Inhabitation
Habitat
Fish
location:
time:
prey biomass:
temperature:
inhabitant
habitat
location:
time:
weight:
Aquatic System
location:
time:
predator weight:
prey biomass:
temperature:

19. 4 (4) Advantages and Disadv
- Easy for modeling and the representation is close to human perception
- Reduce the complexity of software development
Disadvantages

20. 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

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

22. Spatial Types – OGC Simple Features
Geometry
SpatialReferenceSystem
Composed
Type
Relationship
Point
Curve
Surface
GeometryCollection
LineString
Polygon
MultiSurface
MultiCurve
MultiPoint
Line
LinearRing
MultiPolygon
MultiLineString

23. Object-Relational Databases

24. Readings
Chapter 3

25. Object-Oriented and Object-Relational GIS DBMS
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

26. Main Types of DBMS in 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.
Main Types of DBMS in GIS
Rows contain objects
Columns contain object properties or attributes
Data stored in intersection of row and column is value

27. 1. Components of Geographic Data

28. 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

29. Feature Object class Feature class Feature dataset
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