Martin Fowler made a keynote speech at QCon Tokyo on April 9, 2009. He presented an introduction of Domain Specific Language (DSL).

As an example, he showed us a statemachine diagram, a class diagram and Java code. It is not a difficult code, but maybe we can not understand it at a glance. At least, we have to read the code to understand.

However, it's more readable if you use DSL.

He presented several examples such as XML, CSS, regular expressions, Ruby on Rails and DSL.

Since these languages have meaning in themselves, they are more readable than other programming languages like Java.

We can not develop an application by using regular expressions only, but it's easy to understand when we use it as a part in our coding.

DSL also helps business people to understand the application and communicate with programmers. It increases programmer's productivity, too.

He says code generation of DSL is "optional". It is sometimes useful and essential, but still optional. He seems that he emphasizes readability of DSL over code generation.

In conclusion, he said this speech was an introduction of DSL and we would be able to find more articles in his website. He added he would write about DSL in the future (when he has time!).
http://martinfowler.com/bliki/