You've heard all the hype for the past couple of years: Domain Specific Languages (DSLs) are going to take over the world. This session demystifies this topic in 2 ways: by providing concrete definitions for styles and applicability of DSLs and showing how to implement these different styles.

I build up definitions for the different types of DSLs in static (Java) and dynamic (Groovy and Ruby) languages. Then, I discuss building DSLs as internal (i.e., built on top of an underlying language) and external (built using a preprocessor or grammar), with examples of each.

Throughout this session, I discuss the applicability of this style of development and show targeted examples. I discuss fluent interfaces and techniques for building them, including problems. Incidentally, I show some cool language features of both Groovy and Ruby that make building DSLs easier in those languages.