I am designing a data warehouse model in which it seems we would need multiple fact tables. According to what I've read, multiple fact tables doesn't interfere with the theory of the star model. However, it seems that some of the fact tables must "use" other fact tables as dimension tables.
Is that allowed in the star model?
Is it ok anyway, or is it poor design?
I also would like to get useful links to Data Warehouse Design pages on the net. The best I have now is "Data Warehouse Design considerations" on MSDN.
I've been designing databases and data warehouses in Access, Sybase and Microsoft SQL Server for 12 years, and I say screw the star model. It's fine for small, focused, datamarts, but as you've found out real data is much more complex than that. The "snowflake" schema is better, but I always start off with a fully normalized object-oriented data-modeling approach that provides maximum flexibility for storing and querying data. If your database starts approaching the multi-gigabyte size your queries will slow down, but by that time you will have a good understanding of how your data is being used and you can start pre-aggregating data or generating smaller datamarts from subsets of the data.