Hi all, for people that have followed my posts on the DSL subject this question probably will seem strange, especially asking it now. I have read quite a lot lately on the subject, most of it written by the great old ones, (come on guys you know whom I mean :)). What I could gather from their papers was, that a DSL is basically something entirely abstract as such, ie. it allows you build and combine expressions in a language which is specific for your problem domain. Irregardless of further details on how to do that, and there are quite a few, the crux as such is that they are abstract of "meaning". The meaning depends how you *evaluate* the expression, which can be in more than merely one way, which is where, as far as I understand it, the true power lies. So, you might wonder, since I figured it out this far, why ask what a DSL is? Because out there I see quite a lot of stuff that is labeled as DSL, I mean for example packages on hackage, quite useuful ones too, where I don't see the split of assembling an expression tree from evaluating it, to me that seems more like combinator libraries. Thus: What is a DSL? Günther