Martin Fowler has a new book in the making on domain specific languages (DSL). For a while now domain specific languages have been a hot (but under documented) topic in the software development industry.
The idea behind DSLs is to create different programming languages specifically tailored to high level processes like e.g. invoicing, air traffic controlling or software testing. Cucumber is one of the software testing DSLs we use at crealytics to describe program behaviour in plain text.
A good DSL enables concise descriptions of complex behaviours. I believe DSLs will be getting more important in the future, glad Martin fowler is working on that topic.