[rules-users] Drools for spreadsheet style calculation
Hi Drools users,
I'm looking to use Drools to implement spreadsheet style calculation.
Here is an example with cells A, B, C
A = 1;
B = A + 1;
C = A + B;
One way of implementing this is to create a named fact I called Cell.
class Cell{
String name;
double value;
//left out constructor and getters/setters
}
Then the rules can look like this
rule "A"
when
Cell(name == "a")
then
//no-op
end
rule "B"
salience -20
no-loop
when
Cell(a: value, name == "a")
b: Cell(name == "b")
then
b.setValue(a + 1);
modify(b);
end
rule "C"
salience -30
no-loop
when
Cell(a: value, name == "a")
Cell(b: value, name == "b")
c: Cell(name == "c")
then
c.setValue(a + b);
modify(c);
System.out.println("C");
end
Now for this to work I need to first insert the three Cells, a, b, c.
Then anything I update a or b, c will be recalculated.
I want to hear what the experts think of think approach.
Is this optimal?
Can Drools automatically figure out the dependency? (In this case C
depends on A, B and therefore has the lowest salience value).
Can we add a initialization section in the DRL file? (like a static
init block).
--ming