Armstrong’s Axioms in DBMS
Armstrong’s Axioms are a set of rules of axioms. It was developed by William W.Armstrong in 1974. It is used to infer all the functional dependencies on a relational database.
Armstrong’s Axioms are sound in generating only functional dependencies in the closure of a set of functional dependencies (denoted as F+) when applied to that set (denoted as F).
Armstrong Inference Rules in DBMS:
Armstrong’s Axioms has mainly two different sets of rules:
1. Primary Rule
2. Secondary Rule
- Reflexive Rule
- Augmentation Rule
- Transitive Rule
- Decomposition Rule
- Union Rule
- Pseudo Transitive Rule
Given a set of functional dependencies F, an Armstrong relation is a relation which satisfies all the functional dependencies in the closure F+ and only those dependencies. Unfortunately, the minimum-size Armstrong relation for a given set of dependencies can have a size which is an exponential function of the number of attributes in the dependencies.
The Rule of Armstrong Relation:
In the traditional paradigm for designing a relational database scheme, the database designer. It determines a set of attributes and a set of data dependencies among the attributes. This information can be given as input to an algorithm that produces a database scheme satisfying a chosen set of properties