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Answer 5:
Strong Entity: objects are represented by their
attributes and, as objects are inter distinguishable, a subset of these attributes forms a primary key
for uniquely identified an instance of an entity. Entity types that
have primary keys are called strong entities.
Weak Entity: instance
of weak entity sets associated with the same instance of the strong
entity must be distinguishable from each other by a subset of
the attributes of the weak entity. This subset of the attributes is
called discriminator.
One- to – one binary
relationship: the one to one relationships between entity sets
indicates that for each entity in either set there is at most one
entity in the second set that is associated with it.
One- to – many binary
relationship: one to many relationship between entity sets
indicates that for an occurrence of the entity, there could be zero,
one or more entities from the other entity set.
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