Database Management systems

GISs normally store more than one file, ie they contain a collection of files. This means that more complex data management is required and a more elaborate file structure is needed. This is the database structure.

There are four main types of database structure that GIS users need to be familiar with:

hierarchical
network
relational
object oriented

Database management systems (DBMS) are computer programs which are used to organise and manage the database. DBMS aim to make data quickly available to users while maintaining integrity, protecting data against deletion and corruption, and facilitating the addition, removal and updating of data as and when required (Burrough and McDonnell, 1998).

Access to data is usually through a high-level programming language and a user-friendly query language eg the Structured Query Language (SQL) which is the most common query language used (Burrough and McDonnell, 1998).

	Review database structures
1. List the differences between hierarchical, network, relational and object oriented database structures. 2. Which of these do you think might be the best for use in a GIS?

http://www.geog.ubc.ca/courses/klink /gis.notes/ncgia/u43.html#SEC43 This site will provide a description of hierarchical, network and relational database structures. You could also read the Burrough and McDonnell chapter on 'Geographical data in the computer'