ABSTRACT
We will start our review of how spatial data are stored and processed by considering the database technology which is used to store large volumes of data by almost all companies and businesses around the world and see whether this can be used. Many people reading this book may well use databases in their daily work and be very familiar with them. However, many more, and the great majority of the public, will know very little about databases and yet almost everybody will have used a database to access information without ever being aware of the fact. If you have ever used a computer system to book a ticket, look up timetable information, book a holiday, hire a car or purchase anything online, then the system you used to search for the item you wanted and book or purchase it will have been a database system. As far as the user is concerned, a database allows you to search through a large amount of information to find the item or product which suits your needs – a ticket for a particular play or a holiday cottage in the right part of the country at the right time of year. For this to be possible, the database designer has had to organise a large and complex mass of information into a structured format and produce a user interface which allows the user to define their needs in simple terms and which presents the items that may be of interest in a clear manner. The fact that most people use these systems without being aware of how complicated they really are is exactly why databases are so powerful and so useful. To fully understand why databases are so widely used, it is worth knowing a little of the history of their development and this is where this chapter will start. Given their widespread use, they are an obvious choice for the storage of spatial data. However, it turns out that this is not a simple matter. To understand why this is the case it is necessary to understand something about the commonest type of database system, the relational database. With this background knowledge, we will then be able to consider the issues which arise when GIS developers first tried to store spatial data in relational databases.
