1. owner names and times where A was owned
R0
=
select
LandID=A from
Landownership
R0
name
t
landID
alex
0 <= t <= 2
A
tom
2 < t <= 3
A
pete
3 < t <= 7
A
sue
t > 7
A
R1
=
project
R0
on name, t
R1
name
t
alex
0 <= t <= 2
tom
2 < t <= 3
pete
3 < t <= 7
sue
t > 7