raw material ()
raw material (
 rel: or 2 0 vars: a b
 rel: or 2 0 vars: a   c
 rel: or 1 1 vars: a
 rel: or 1 1 vars: b
 rel: or 1 1 vars:   c
 )
raw material (
 rel: or 2 1 vars: a b      //or(a !b): positives come first
 rel: or 2 1 vars: c b    //or(!b c): notice the order 
 )