I had a conversation with a former discretionary daytrader who has spent a year developing systems. We seem to have a friendly disagreement about optimizing. What constitutes curve fitting and what type of optimizing might be useful in indicating future profitability. Also when do adaptive tools become over fitting. If anyone wants to advise others on this subject, I for one will listen as I have not done too much system designing and would be afraid to trade any system that would be optimized because I know sometimes optimization leads to curve fitting. So when if ever is it a a good thing. (Side note) I would be able to trade say a breakout system that was tested over many parameters and I got to choose a setting from within an area that showed solid returns. However, to me that is not what my friend is doing when he talks about optimization. (I believe he has been mislead by Indigo and would like to see him stop wasting his time, however I am very aware I could be wrong because this is not my forte by any stretch.) As I write this I see the need for definitions and explanations and I am all ears. Thanks any help will be appreciated.