Suppose a scenario where there are Cats and they can be Male or Female, Black or White. They form two disjoint complete partitions of Cat. To represent this scenario I've come up with three diferent solutions, and would like some advice on which is the best, regarding computer effort
I'm concerned if the use of the universal quantifier is so bad it's worse than declaring 4 other functions. Consider also if there were more classes involved.. There would be more intersecting subclasses...

Solution 1:
sig Cat{}
sig Male in Cat{}
sig Female in Cat{}
sig Black in Cat{}
sig White in Cat{}
fact generalization_sets
{
   all c:Cat | (c in Male || c in Female) and (c in Black || c in White)
}

Solution 2:
sig Cat{}
sig Male in Cat{}
sig Female in Cat{}
sig Black in Cat{}
sig White in Cat{}
fact generalization_sets
{
   disj[Male,Female]
   disj[Black,White]
   all c:Cat | (c in Male + Female) and (c in Black + White)
}

Solution 3:
sig Cat{}
sig Black_Male extends Cat{}
sig Black_Female extends Cat{}
sig White_Male extends Cat{}
sig White_Female extends Cat{}
//use functions to refer to each separate subclass
fun Black:Cat{Black_Male+Black_Female}
fun White:Cat{White_Male+White_Female}
fun Male:Cat{Black_Male+White_Male}
fun Female:Cat{Black_Female+White_Female}