1. Database Truth of the Week

"For the operations of a formal system to have inverses within some specific use of that system (like a specific application):

• The basic elements must be orthogonal (independent), hence the Principle of Orthogonal Design;
• The combination of basis elements and operations must be expressive enough to represent every aspect of the subject matter, hence the Principle of Expressively Complete Design;
• And, at the same time, not so expressive that there is more than one way to express each aspect of the subject matter, hence the Principle of Representation Minimality Design.

The basic elements of a relational database is the relation. Adherence to these principles ensure thatthere is a unique relational expression for every aspect of the subject matter--either a base relation or a derived relation--and if there are two ways to derive a derived relation, then those two expressions are provably equivalent (i.e., the differences are merely syntax and never meaningful)." --David McGoveran

• Data Meaning and Mining: Knowledge Representation and Discovery

1. Database Truth of the Week

"The RDM is a formal system. It has two parts.

• The Deductive Subsystem: the formal language
• The Interpretation Subsystem i.e., the application--of that language

Without an interpretation subsystem there is no possibility of applying the formal system and it remains an abstract game of symbols.

Semantics is about applying the RDM to some subject. In effect, what you do is restrict the power of the abstract formalism so that it is more closely aligned with your intended use. That means you are using constraints to limit the vocabulary to the subject matter (and making it finite and usually fairly small) and restricting the possible interpretations that can be used consistently with the resulting subset of the formalism." --David McGoveran

What Meaning Means: Business Rules, Predicates, Constraints, and Semantic Consistency