What is the definition of interface layer and data definition layer and Entity Relationship Diagram?

well what is interface layer and data definition layer I could not remember .. but I can help you about entity relationship diagram.

as the name tells it shows the enties and relationships among them, it is used before making a database schema. like you are desinging a database system , so you have to specify the entities that you are going to store in the database , next is relation among them.. that is one to one , one to many or many to one , like that ,, all that should be shown in entity relationship diagram, in entity relationship diagram you have to draw these relation . , relation can be of other types also .. dependency ..like presence of one entity is dependent on another entity .. like for example ..( primary key , foreign key relationships)

Interface layer - The layer in Internet protocols responsible for transmission on a single physical network.

Do you mean data link layer? Layer 2 of the OSI model, it defines protocols involving data packeting and transmission into and out of each network (nodes).

Entity Relationship Diagram - A representation of the entities and the relationships between them. Used to achieve a common understanding of data among users and application developers.

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