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. 2 Levels of Data Abstraction … Increasing abstraction Reality Conceptual Model Logical Model Physical Model Human- oriented Computer- oriented

5. 3 Database Functions ► ► Records, fields, and keys - a row is a record - a column is a field

6. 3 Database Functions … ► ► Map librarian and tiles

7. 3 Database Functions … ► ► Adding, updating and deleting records ► ► Extracting information from data ► ► Maintaining data security and integrity ► ► Supporting applications

8. 4 Database Data Models (Logical Models) ► ► Hierarchical data model ► ► Network data model ► ► Relational data model ► ► Object-oriented data model

9. 4 (3) Relational Data Model ► ► The database consists of several tables ► ► A row is a record and a column is a field

10. 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 field is common to both files ► ► A link table can be created with needed attributes, without taking actual storage space

12. 4 (3) Advantages and Disadv ► ► Advantages - Flexible, no structure restrictions for search - Easy to understand - Less data redundancy ► ► Disadvantages - There ay be 1:M or N:M relationships between tables

13. 4 (4) Object-Oriented Data Model ► ► Encapsulation ► ► Objects, attributes, processes ► ► Inheritance ► ► Association and aggregation

14. 4 (4) Object-Oriented Data Model.. ► ► Encapsulation - Data (attributes) and functions (processes) are combined in one object

15. 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

16. 4 (4) Object-Oriented Data Model.. ► ► Association and aggregation a member of vs. a part of Fish location: time: weight: Aquatic System location: time: predator weight: prey biomass: temperature: Habitat location: time: prey biomass: temperature: inhabitant habitat Inhabitation

17. 4 (4) Advantages and Disadv ► ► Advantages - Easy for modeling and the representation is close to human perception - Reduce the complexity of software development ► ► Disadvantages - Most existing object-based systems are a hybrid of relational and object-based databases

18. 4 (4) 4 (4) Object-Relational Databases ► ► Use an enriched set of graphic element types on top of the three basic types of points, lines, and polygons

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

20. Readings ► Chapter 3

21. Object-Relational Databases..

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

23. Spatial Types – Oracle Spatial DB2 Spatial Extender ArcSDE/ArcGIS Server