Often there are four distinct aspects, as you might have seen in some of my stories and/or 'bites', the main reason follows from the following Boolean Algebra, i.e. Boolean Table, which is fundamentally based on only two binary digits: 0 and 1; which is the basis of digital computing:
0 0
0 1
1 0
1 1.
Thus, you can put two attributes: one as 0 and the other as 1; and fill the table appropriately. But, in the final analysis it should have collectively some sensible meaning.
