When blogging about DSLs, I’m mostly blogging about internal domain-specific languages, because jOOQ is a good example for internal DSLs. But external domain-specific languages are an interesting topic as well. As an external DSL does not depend on any host language (e.g. Java), it can be much richer in syntax and expressivity. On the other hand, you need tools to parse, compile and maybe even interpret / run them.
Here’s a very interesting blog post showing how to create an external DSL with Xtext, Eclipse’s DSL tool chain. It creates a simple DSL to describe video game control flows and shows how Eclipse Xtext immediately provides an editor with all sorts of IDE features for that custom DSL:
http://www.altdevblogaday.com/2013/07/19/creating-powerful-languages-with-xtext