Design Methodology: A structured approach that uses procedures, techniques, tools, and documentation aids to support and facilitate the process of design?

An Entity is an object or thing we wish to store information about, and when we group a set of objects with the same properties, having an independent existence as an entity

Relationships are associations between entities and are given a name to represent its function

Entity attributes can be simple or composite, single or multi-valued and derived?

A primary key must be made of two columns that are unique within that table

In a relational database, relationships are expressed by foreign keys, linking one entity instance to another

A many-to-many relationship does not allow this relationship expression, because each record in each table may point to multiple records in the other table.

Developing an ER Model involves the following steps:
Step 1 – Identify entities,
Step 2 – Work out relationships,
Step 3 – Identify attributes,
Step 4 – Identify optionality,
Step 5 – Identify key attributes,
Step 6 – Create data dictionary