Concept of the relational model

In contrast to the entity-relationship-model (ERM) which is a conceptual model, the relational model is a logical data model. It can be seen as lying one step or layer below the ERM. The relational model is not about abstract objects but defines how data should be represented in a specific database management system. The goal of a logical data model is to arrange the data in such a form that it is consistent, non-redundant and supports operations for data manipulation.