- countries
name
area
population
gdp
("gross domestic product")
- cities
name
population
longitude
latitude
- rivers
name
length
- seas
name
max
depths
Model the following relationships between the geographical
objects:
- each city belongs to exactly one country
- each river crosses one or several countries
- each river ends in another river or in a
sea
Consider a relation with schema R(A,B,C,D) and an unknown set of functional dependencies. For each closed attribute set below, give a set of functional dependencies that is consistent with it.