In 2004 a colleague told me about code kata. These are the good exercises to do when learning a new language, or just empirically solve some common problems. One of the puzzlers sit in my mind permanently since then - The Business Rules Kata, which is about the hard to maintain complex business rules.
How can you tame these wild business rules? How can you build a system that will be flexible enough to handle both the complexity and the need for change? And how can you do it without condemming yourself to years and years of mindless support?
We face all these problems daily while coding the business logic for our banking system. One of the approaches some developers have taken is that
the if-the statements can be avoided while using appropriate OOP techniques
The problem is that sometimes while avoiding those if-statements the code becomes over-engineered due to a large number of classes. And it is still doesn't solve the problem of quick changes that are very hard to implement in a big organization with the "release process".
Recently I've found a discussion at joelonsoftware.com. It is dated 2005 but I think not much have changed since then. I think that most of the developers are still fighting the complexity of the business rules and in future it will still be a challenge.
My next step is to create a demo using JBoss Drools, QuickFIX/J. Apache Camel can be used to integrate both into one flow.
Also what is really cool about Drools is that it would allow our clients to maintain the order validation rules apart of the overall release process using Guvnor. So the changes in order validation logic could be introduced rapidly.