Structural ER Model
Structural ER Model
Describes connections among data entities,
complementary to data descriptionsname
- Ownership
- Part-of
- Reference
- Subset
Connections are also manipulated by the relational algebra
Instances of connections are links among data objects,
existing whenever the data values match
primary
pat
car
pat
staff
secondary
visits
wheels
country
nurse
cardinality
1 : n
1 : n
n : 1
1 : 1 partial