Uh, all ISO Prolog programs run on all ISO Prolog implementations, regardless of what extensions a particular implementation has. Same for RxRS Scheme. And VH

Uh, all ISO Prolog programs run on all ISO Prolog implementations, regardless of what extensions a particular implementation has. Same for RxRS Scheme. And VHDL and C99 definitely aren't "families" of languages. GCC, Clang, ICC, and maybe even MSVC all interpret the same code semantically equivalently. Unless you can either show C99 to be unsuccessful, find a reference implementation of C99, or define "interpreted" in a meaningful way, I think your assertion doesn't hold.