Field names are descriptive. Words are separated by underscores, separate words are capitalized, and abbreviations are avoided where possible. Where abbreviations are required, they are used consistently. Field names are consistent across all tables.
All tables are in, at least, third normal form.
For every table defined, at least one view is required. As many other views may be defined as are necessary. Application software refers to views instead of the tables themselves. This insulates the application from changes that are made to the underlying tables. All tables, with the possible exception of very small ones with limited growth potential, include a primary key to guarantee uniqueness and enhance performance.