Geographic Information Systems GIS Data Databases

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 database management system (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 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)

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

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

3 Database Functions … Map librarian and tiles

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

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

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

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

 

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

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

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

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 Four legs, sit Fish Fins, swim

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

4 (4) Advantages and Disadv - 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

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

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

Readings Chapter 3

Object-Relational Databases..

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

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