MAKE |
MODEL |
M1 |
A |
M2 |
C |
M1 |
B |
M2 |
D |
Now consider make--> model
make alone cannot distinguish different models
like in above example for M1 you get A as well as B not a unique make hence this is invalid.
Now consider model --> make
given any model we can clearly tell to which make it belongs. as any model can only associate with only one make.
eg. given A we can clearly conclude that make is M1
hence model --> make is valid .