From the very beginning (around 1978) the intention was to use a language for modelling:
"We stress here... that the meta-language is to be used, not for solving algorithmic problems (on a computer), but for specifying, in an implementation-independent way, the architecture (or models) of software. Instead of using informal English mixed with technical jargon, we offer you a very-high-level 'programming' language. We do not offer an interpreter or compiler for this meta-language. And we have absolutely no intention of ever wasting our time trying to mechanize this meta-language. We wish, as we have done in the past, and as we intend to continue doing in the future, to further develop the notation and to express notions in ways for which no mechanical interpreter system can ever be provided."