Tip. If there are only a few assumptions that will fit comfortably on the diagram, place them there. Otherwise, place them on a separate sheet. Always include assumptions.
Completing the following tasks sequentially will create an E-R diagram
Entities: Identify all of the entities involved
Relationships: Determine the relationships between each entity
Associative entities: Decide if any of the relationships are candidates to be associative entities
Attributes: Identify the attributes for each entity in turn, paying particular attention to:
• Multi-value attributes
• Derived attributes
Note. Composite attributes do not need to be broken down to their atomic form at this point
Primary Key: Identify the attribute that is the unique identifier for each individual instance of an entity.
Note. This is not always possible at this point. If a unique identifier cannot be identified, the problem is resolved when the E-R diagram is mapped to the logical model.
Assumptions: Include any assumptions made (this can also contain data definitions).