9.1 The Entity Relation Model

	One of the most widely used approaches for database conceptual modelling is the Entity-Relationship (E-R) model which was introduced Peter Chen in 1976.
	The E-R model includes representations describing objects such as entities, relationships and attributes.
	The E-R model includes a graphical representation known as E-R diagrams.
	Each object has a graphical representation in the E-R model.
	Different E-R objects are discussed in the following sections of this lecture and in Lecture 10.