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