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.
The crucial part of the ER model are the relations with which the instances are set in relation to each other. Simple relations are for example the name of a person to its residence, or the conversion for a product in relation to the coworkers of a department, or all actions, which result in connection with the production of a product, in relation to the total costs are set.
The ER model is independent of a particular database system and is used to analyze and design data structures. It supports the creation of new application systems by providing a logical data model that supports the physical implementation.
To represent the relationships between entities such as customer, address, or position, ER models use specified graphical components such as arrows and rectangles. For example, single and double arrows are used to indicate relationships among entities.
The ERM representation is used to check the relationships among each other.