The real power of this approach is when we start combining signals. So far, we've only looked at moving averages (lagging indicators) and Bollinger Band signals (leading and confirming indicators). But, there are many more strategies that you can employ to make financial decisions.
What should be emphasized is the focus on taking normal business rules and applying them directly with a set of filters, list transformations, and so on, to yield a system that provides us with valuable business information. We've taken our lagging indicator functions (SMA, EMA, and Bollinger Band) and composed them together to get new information—buy or sell signals.