Design Goals

Your goal is to design databases that are:

Comprehensive: Every item of information that is relevant to the organization should be recorded (provided that it is cost effective to do so).
Non-redundant: Every item of information should appear only once. This not only saves resources, but also ensures that the data is concurrent; that the computer does not hold two conflicting versions of what should be the same item of data.
Consistent: There should be no mutually incompatible representations of information, nor conflicting rules about what can be done with the data, so that system data integrity can be preserved. Data modeling can assist you to achieve this aim.
Efficient: The access times to retrieve or process data should meet the business requirements. Some consideration of the processes that will operate upon the database is necessary to check that this aim is satisfied.