Relational design theory

The relational design theory focuses on the basis of formal methods with the conceptual design of the schemes of relational databases . Relational design theory thus offers a theoretical basis for designing a good relational scheme.

Functional dependencies form the basis for the design of a schema , which - informally - are a generalization of the key term with the help of which certain stored data can be clearly identified. Furthermore, the canonical coverage of functional dependencies and multi-valued dependencies are the subject of the investigation; the latter are in turn a generalization of the functional dependencies.

The functional dependencies are used to define normal forms for relational schemes; they represent a quality criterion on the basis of which the quality of relation schemes is assessed; Quality is a collective term for properties such as manageability, comprehensibility, clarity, etc. Relational design theory tries to formalize this concept of quality using normal forms.

A good relational schema is characterized, for example, by the fact that information is not stored implicitly, that information is not stored redundantly , and that no inconsistencies caused by change, deletion and insertion anomalies occur. Such undesirable properties of relational schemes are often caused by mixing, decomposing or repeated storage of the entities identified in the information needs analysis .

There are two approaches in relational design theory:

• The normalization of relations helps to improve a given design: If certain normal forms are not fulfilled for a relation scheme , this can be broken down into several schemes with the help of appropriate normalization algorithms, which then fulfill the desired normal form.
• The synthesis of relations aims at the construction of an optimal relational schema.