For AndroMDA 4, I designed a plugin registry configuration language and a workflow language, both of them based on XML. After some time, I found out that this was not the best choice. XML can become complex and wordy and it lacks real good tool support (did you ever try to run a unit test on an XML document?). 🙂
So, after all that hype about Groovy in the current software development magazines, I decided to give it a try. And guess what? Within 4 hours, I learnt the language and became fond of it. It took me another 4 hours to throw away the XML-based configuration in AndroMDA 4 and replace it by Groovy. Now, I am satisfied – it is much easier to configure the generator than before.