From what I observe we haven’t found a good model for configuration languages yet, in the space between pure data on the one end and Turing-complete languages o

From what I observe we haven’t found a good model for configuration languages yet, in the space between pure data on the one end and Turing-complete languages on the other. In particular if the languages are also aimed at non-developers, like traditional, mostly key-value configuration files are (INI files, many Unix configuration file formats). As is often noted, the goal of avoiding Turing-completeness is a red herring, because restricting a language to (say) primitive-recursive functions still easily allows programs that don’t halt in any remotely practical time, and effectively still allows to emulate Turing machines up to some large if finite upper bound of execution steps. We want some expressiveness and some ability for functional abstraction in our configuration languages (variable substitutions, simple macros, and the like), but we also don’t want them to become full-blown programming languages allowing arbitrarily complex programs. However, it’s not clear that there really is a sensible and principled middle ground.