EERD Flashcards
(3 cards)
1
Q
What is the disjointness constraint in EERD
A
An entity can be a member of at most one of the subclass entities
2
Q
What is the difference between a hierarchy and a lattice
A
Hierarchy is a tree structure, whereas a subclass in a lattice can have multiple superclasses
3
Q
What is a union type / category?
A
When a superclass represents more than one entity type
