What I was thinking of was this one: https://en.wikipedia.org/wiki/Planner_(programming_language)#Micro-planner_implementation https://en.wikipedia.org/wiki/Pla

What I was thinking of was this one: https://en.wikipedia.org/wiki/Planner_(programming_language)#Micro-planner_implementation https://en.wikipedia.org/wiki/Planner_(programming_language)... . I don't imagine there's any more formal a specification beyond what-they-implemented (but I haven't actually read the paper!)