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database management

GI Systems and Science January 30, 2012. database management. Points to Cover. Recap of what we covered so far A concept of database Database Management System (DBMS) Database data models Relational database model Object-oriented approach

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database management

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  1. GI Systems and Science January 30, 2012 database management

  2. Points to Cover • Recap of what we covered so far • A concept of database • Database Management System (DBMS) • Database data models • Relational database model • Object-oriented approach • Relationship between spatial and attribute data in GIS • Data management operations in ArcGIS

  3. Spatial Data Modeling

  4. Data Types in GIS Spatial data Attribute data

  5. Concept of Database • A GIS can be described as a spatially-enabled database • Conventional databases store attribute data • GIS stores both attribute and spatial data • Database is a set of structured data that are related to each other in some way • Organized filing cabinet • Phone book • On-line database of academic publications

  6. Concept of Database • Many of human activities produce data that is stored and managed in the database environment • Our society is generating tremendous amounts of data on daily basis • Data has become a valuable commodity • To realize its value, the data need to be managed and shared efficiently

  7. Concept of Database • One of the approaches to turning data into information is a database • Database is more than just a container for storing data • Organize data into more meaningful and usable form • Have analytical capabilities

  8. Concept of Database • The database approach provides the following benefits • Ease of accessing data • Prevention of unnecessary duplication of data • Data stored independently of the application for which they are used • Secure controlled access to data • Standards facilitate data exchange • Data in the database can be shared by different users • Manual databases versus computer databases • Which are more effective and efficient?

  9. Database Management System • A DBMS is a computer program that controls the storage, retrieval and modification of data in a database (Dale and McLaughlin, 1988) • Comprises tools that perform these functions • Allows users to deal with the data without knowing much about the database itself Figure 4.4 Source: Heywood et al., 2011

  10. Relational Database Data Model • A DBMS manages data that are organized using a database data model • Set of rules about how the objects and relationships between them should be represented • Number of different data models used for handling attribute data in GIS • Relational data model is most used by GIS • The relational data model is based on concepts proposed by Frank Codd (1970)

  11. Relational Database Data Model • Data are organized and stored in a series of two-dimensional tables, each of which contains records for one type of entity • Each entity has a unique identifier value assigned to it • Unique identifiers allow to link (relate) data in two or more different tables • This structure makes possible applying queries to one or more tables

  12. Relational Database Data Model • Types of relationships possible between entities in a relational database Figure 4.7 Source: Heywood et al., 2011

  13. Relational Database Data Model Figure 4.8 Source: Heywood et al., 2011

  14. Relational Database Data Model • Querying a relational database • Queries are built on expressions based on relational algebra which in turn is based on Boolean logic • SQL, standard query language, has been developed to facilitate the querying of relational databases • Advantages: completeness, simplicity, pseudo-English language style • Disadvantages: was not developed to handle geographical concepts such as ‘near to’, ‘far from’ or connected to

  15. Object-Oriented Database Approach • More realistic approach to representing spatial entities in the database environment • Encapsulation: Object = State + Behaviour • State: set of values of attributes describing a spatial entity • Behaviour: methods of operating on it • Composite object • Hierarchy of objects • Subclass • Superclass Figure 4.17 Source: Heywood et al., 2011

  16. Object-Oriented Database Approach • Allows arranging objects into hierarchies allows differential assignment of behaviours (Inheritance) • Behaviour of subclass objects = ‘own’ behaviour + ‘superclass’ behaviour • Benefits of the OO approach for GIS • No differentiation between spatial and attribute data • Works better for graphic operations • Disadvantage of the OO approach • Represents world as a series of rigidly bounded objects • Still under development

  17. Data management in ArcGIS • The primary data storage mechanism in ArcGIS is the geodatabase • A collection of geographic datasets of various types held in a common ‘container’ such as a database file or a database application • Based on an object-relational model • Relations (tables) function as objects • Behavior is supplied through the geodatabase application logic implemented as a series of system tables • A key geodatabase strategy is to leverage the database management system (DBMS) • Extends SQL application to feature geometry

  18. Data management in ArcGIS • Geodatabases comprise • Three primary dataset types • Feature classes • Raster datasets • Tables • Database schema: metatables containing information about object behavior and relationships, maintaining data integrity • Topologies • Networks • Subtypes Source: ArcGIS 10 Help files *

  19. Data management in ArcGIS • Types of geodatabases • File geodatabases • Stored as folders in a file system. • Each dataset is held as a file that can scale up to 1 TB in size. • Personal geodatabases • Datasets are stored within a Microsoft Access data file • Limited in size to 2 GB • ArcSDEgeodatabases • Stored in a relational database using Oracle, Microsoft SQL Server, IBM DB2, IBM Informix, or PostgreSQL. • Multiuser geodatabases which are unlimited in size

  20. Data management in ArcGIS Figure 4.9 Source: Heywood et al., 2011

  21. Relationship between data in GIS • Raster datasets • Simple raster datasets • no separate attribute data table • Rater datasets with attribute tables • Within a geodatabase, the raster attribute table is saved within the raster dataset and hidden from the user * Source: ArcGIS 10 Help files

  22. Relationship between data in GIS • Vector datasets

  23. Data Management Operations • The supported attribute column types in the geodatabase Source: ArcGIS 10 Help files

  24. Data Management Operations • Queries • Attribute query • Used to find features based one particular attribute • Locational query • Used to find features with locations that meet certain conditions • Works with four types of relationships: near, adjacent to, intersect, and inside • The result of queries is a set of selected features

  25. Data Management Operations • Joins • Associating two or more tables based on a common field (key) One-to-one relationship One-to-many relationship

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