A schema is the document used to define how your dimensions and measures map to your data source. In its raw form it is an XML document which describes the physical table structure and how those tables link together, and it describes your cubes, and the dimensions and measures they each contain.
Advanced Date Filtering - Learn how to use the Advanced Date Filter, for period on period filtering etc.
Conditional Formatting - How to make cells behave differently when different measure values are returned
Using Saiku Schema Designer - Create schema without a text editor using Saiku Schema Designer
Mondrian in Action - The Definitive Mondrian 4 book
Foodmart test schema - The Foodmart schema which powers the test suite and demo data, covers most use cases
Schema auto generated documentation - Find out what the various schema attributes do in Mondrian 4