4. time periods where sara was hit by hurricane
R0 = join landowner and Land
R0
name
t
 landID
x, y
tom
t>2,t<=3
 A y-x<=2,x<=5,y>=1,y<=5
sue t>7 A y-x<=2,x<=5,y>=1,y<=5
alex t>=0,t<=2 A y-x<=2,x<=5,y>=1,y<=5
pete t>3,t<=7 A y-x<=2,x<=5,y>=1,y<=5
sara t>=0,t<=4 E y>=1,y<=3,x>=5,x<=10
sue t>6,t<=9 E y>=1,y<=3,x>=5,x<=10
kim t>4,t<=6 E y>=1,y<=3,x>=5,x<=10
alex t>9 E y>=1,y<=3,x>=5,x<=10
kim t>6 D y>=3,y<=5,x>=5,x<=10
john t>=0,t<=2 D y>=3,y<=5,x>=5,x<=10
sara t>3,t<=6 D y>=3,y<=5,x>=5,x<=10
sam t>2,t<=3 D y>=3,y<=5,x>=5,x<=10
sue t>1,t<=4 C 2y-x<=7,y>=5,x<=10,x>=7
pete t>7 C 2y-x<=7,y>=5,x<=10,x>=7
pete t>=0,t<=1 C 2y-x<=7,y>=5,x<=10,x>=7
john t>4,t<=7 C 2y-x<=7,y>=5,x<=10,x>=7
kim t>3,t<=5 B y>=5,y<=7,x>=3,x<=7
same t>8 B y>=5,y<=7,x>=3,x<=7
tim t>=0,t<=3 B y>=5,y<=7,x>=3,x<=7
alex t>5,t<=8 B y>=5,y<=7,x>=3,x<=7
R1 = select name=sara from R0
R1
name
t
 landID
x, y
sara t>=0,t<=4 E y>=1,y<=3,x>=5,x<=10
sara t>3,t<=6 D y>=3,y<=5,x>=5,x<=10

R2 = join R1 with hurricane
R2
name
t
 landID
x, y
sara t>=0,t<=4,t>=1,t<=3 E y>=1,y<=3,x>=5,x<=10,2x-2y=15,2x>19,2x<=23
sara t>=0,t<=4,t>3,t<=4 E y>=1,y<=3,x>=5,x<=10,y=2,x>=3,2x<=19
R3 = project R2 on t
R3
t
t>=0,t<=4,t>=1,t<=3
t>=0,t<=4,t>3,t<=4