Variables and relations
The elementary relation in a decision diagram is equality between a variable and a value in its domain, for example i == 5.
Normally, there is more than one variable, and relations use combined equalities through conjunction (the and operator) and disjunction (the or operator).
Example:
X ::= (i == 5 and j == 1)
or (i == 2 and j == 1)The example shows a relation named X that holds when j is equal to 1, and i must be either 2 or 5.
The library itself provides constant relations ONE to express true (the relation that always holds), and ZERO to express false (the relation that never holds).