I am making a 2X2 sudoku game, modeled after Nqueens example. A `Digit` class is assigned a `column` and `row` object. The `row` is the planning entity. But a sudoku game also has a `block`, which is to be calculated from `row` and `column`. Two digits cannot share a block. A block is null when the row is null, and a numerical value that will be equal for all digits in the row. Question: where do I tell the `Digit` object to recalculate it's `block`? I did it in doMove, but it is misses most places the object is updated (as per my attempts at logging). Must I set it to update itself when the `row` property of the object changes, say at `setRow()`? A 2X2 sudoku: http://mypuzzle.org/sudoku/kid.html private integer block; ... public Integer getBlock(){ return block; } public void setBlock(int not_used){ if(this.row==null) this.block=null; else this.block=10*(this.row.getIndex()/2)+this.column.getIndex()/2; } -- View this message in context: http://drools.46999.n3.nabble.com/Where-do-I-code-the-calculation-for-a-d... Sent from the Drools: User forum mailing list archive at Nabble.com.