I have a strong feeling that database design and normalisation often comes in second hand when dealing with spatial data.
With software costing a fortune and databases with over 100 fields tables I have to ask:
Is there good reasons for taking other considerations than normalisation when designing a spatial database?
I guess people will ask for examples, but that I can not give here, so my question is maybe more aimed for those who means that 100 fields is no problem and easier to maintain than a proper normalized design.
What are the arguments?
Best Answer
I feel that spatial databases should be treated no differently to traditional databases. They are essentially doing the same thing, storing large amounts of data for fast retrieval. As an example, in PostgreSQL / PostGIS, the geometry is just another datatype. Just like text, or integer. Same in SQL Server 2008. Same in Oracle. If the "spatial" part is just another field type in the database, then is it really that different from the original database? Does this mean we should throw out all the rules of traditional database design?
Obviously normalization can be taken too far, just as with traditional databases, so it's a trade off to find the best design that suits your needs.
If you are planning on created a highly de-normalized structure with tables of 100 columns, then you have to ask yourself what is likely to change in the future? With a vast increase in rows, is this also going to affect querying performance? Is this going to affect maintainability in the future?
What's wrong with created a normalized structure and using views to expose all the data to the database client, be it GIS, or any other client?
All of these questions apply to both traditional databases and spatial databases. If you go through http://en.wikipedia.org/wiki/Database_normalization you will find that it applies to spatial databases as well.
If the software you are using on top of the database is forcing you to use highly de-normalized structures, then this is a different argument. You are constrained by the software and not the database, so you have no choices in the best database design.
So I think, the short answer is (in my opinion) database design is just as important with spatial databases as with traditional databases.