! kermit = frog("Kermit", 3, 4).
Not sensible
! kermit = green("Kermit").
Sensible
! kermit = yellow("Kermit").
Not sensible
! kermit = yellow(3,4).
Sensible
Match yellow(x,y) =~ yellow(4,7).
Sensible
Match green(s) =~ yellow(4,7).
Not sensible