Composite attributes = are objects that are part of another entity
relationships can have attributes
relationship types can be many to many, 1 to 1, 1 to many
e.g. an employee can work on many projects and projects can have many employees
key attribute is an unique identifier
weak entities are ones that do not have key attributes
Naming conventions - singular (not plural)
absolute relationships - “must be” - double line
conditional - “can be” - single line
specialization - defining subclasses
- disjoint d means a class can/must only one of the subclasses
- overlapping means it can/must be any
- can/must depends on
Union - a new class created that can be one of a group of classes
- e.g. if there are three options - Bishop, King, Queen - you could create a class called ‘Chess Piece’ that has those 3 as possible types//