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