The Entity Relationship Model (ERM) or ER model is a graphical tool for the design of databases. In this model, the real relationships of events, actions, objects or applications are modeled and set in relation
to each other. Thekey of the ER model are the relationships with which the instances are set in relation to each other. Simple relations are, for example,
the name of
a person to his place of residence, or the turnover for a product in relation to the employees of a department, or all actions that occur in connection with the creation of a product are set in relation to the total costs.The ER model is independent of a specific database system and is used for the analysis and design of data structures. It supports the creation of new application systems by providing a logical data model that supports the physical implementation
, or location, ER models use specified graphical components such as arrows and rectangles. For example, single and double arrows are used to indicate the relationships among entities, and the ERM representation is used to verify the relationships among entities.