1. Creating and Maintaining Geographic Databases

2. Outline Definitions Characteristics of DBMS Types of database Relational model SQL Spatial databases

3. Definitions Database – an integrated set of data (attributes) on a particular subject Geographic (=spatial) database - database containing geographic data of a particular subject for a particular area Database Management System (DBMS) – software to create, maintain and access databases

4. A GIS can answer the question: What is where? WHAT: Characteristics of attributes or features. WHERE: In geographic space.

5. A GIS links attributes to spatial data Attribute Data Flat File Relations Map Data Point File Line File Area File Topology Theme

6. Flat File RecordValue Attribute RecordValue RecordValue

7. Advantages of Databases over Files Avoids redundancy and duplication Reduces data maintenance costs Applications are separated from the data –Applications persist over time –Support multiple concurrent applications Better data sharing Security and standards can be defined and enforced

8. Disadvantages of Databases over Files Expense Complexity Performance – especially complex data types Integration with other systems can be difficult

9. Types of DBMS Model Hierarchical Network Relational - RDBMS Object-oriented - OODBMS Object-relational - ORDBMS

10. Historically, databases were structured hierarchically in flat files...

11. Relational Databases rule now

12. Characteristics of DBMS Data model support for multiple data types –e.g MS Access: Text, Memo, Number, Date/Time, Currency, AutoNumber, Yes/No, OLE Object, Hyperlink, Lookup Wizard Load data from files, databases and other applications Index for rapid retrieval

13. Characteristics of DBMS Query language – SQL Security – controlled access to data –Multi-level groups Controlled update using a transaction manager Backup and recovery

14. Characteristics of DBMS Applications –Forms builder –Reportwriter –Internet Application Server –CASE tools Programmable API

15. Geographic Information System Database Management System Data load Editing Visualization Mapping Analysis Storage Indexing Security Query Data System Task Role of DBMS

16. Relational DBMS Data stored as tuples (tup-el), conceptualized as tables Table – data about a class of objects –Two-dimensional list (array) –Rows = objects –Columns = object states (properties, attributes)

17. Table Row = object Vector feature Column = attribute

18. Relational DBMS Most popular type of DBMS –Over 95% of data in DBMS is in RDBMS Commercial systems –IBM DB2 –Informix –Microsoft Access –Microsoft SQL Server –Oracle –Sybase

19. Relational Join Fundamental query operation Occurs because –Data created/maintained by different users, but integration needed for queries Table joins use common keys (column values) Table (attribute) join concept has been extended to geographic case

20. Relational Databases

21. SQL Structured (Standard) Query Language – (pronounced SEQUEL) Developed by IBM in 1970s Now de facto and de jure standard for accessing relational databases Three types of usage –Stand alone queries –High level programming –Embedded in other applications

22. Types of SQL Statements Data Definition Language (DDL) –Create, alter and delete data –CREATE TABLE, CREATE INDEX Data Manipulation Language (DML) –Retrieve and manipulate data –SELECT, UPDATE, DELETE, INSERT Data Control Languages (DCL) –Control security of data –GRANT, CREATE USER, DROP USER

23. Spatial Search: Gateway to Spatial Analysis Overlay is a spatial retrieval operation that is equivalent to an attribute join. Buffering is a spatial retrieval around points, lines, or areas based on distance.

24. Image courtesy of K. Foote/M. Lynch, UT-Austin Overlay

26. Overlay like an attribute join

27. Types of overlay operations Union Intersect Identity Max Min Etc.

28. Union computes the geometric intersection of two polygon coverages. All polygons from both coverages will be split at their intersections and preserved in the output coverage.

29. Intersect computes the geometric intersection of two coverages. Only those features in the area common to both coverages will be preserved in the output coverage.

30. Identity computes the geometric intersection of two coverages. All features of the input coverage, as well as those features of the identity coverage that overlap the input coverage, are preserved in the output coverage.

31. Buffer

33. Complex Retrieval: Map Algebra Combinations of spatial and attribute queries can build some complex and powerful GIS operations, such as weighting. Weighted overlay analysis really just complex retrieval.

34. Map Algebra Combined with