Evgeny Rahman and Jarrod Bellmore from the Worcester Polytechnic Institute have investigated a method for defining DSLs based on the Rational Unified Process. Hats off for their thesis work. While I will not argue the suitability of RUP for defining DSL's (I can imagine a whole future battle between DSL-RUP aficionado's contra Agile DSL guerilla's), I do have much respect for the topic choice they decided on for their thesis work. Defining DSL's certainly will be a key issue. Now that the technology is there and more vendors announcing support for DSM, the next obstacle that those wanting to adopt DSM will be faced with, will be "Ehrrrrrr.....so how do we actually define our own modeling language"?
Next-generation DSM tools may even offer support for various DSL definition processes, including the creation of all documentation for decision making processes during the DSL definition and maintenance. Remember that like developers today, language designers will change jobs in the future and for those that replace them good documentation about the choices made by their predecessors about the DSLs in use and their evolution over time, will help in making future decisions on where to go with the languages in use.