Sorry, my earlier use of the word subset was a mistake and I have edited the sentence in question to say "within the purview" which is more what I had in mind.

Sorry, my earlier use of the word subset was a mistake and I have edited the sentence in question to say "within the purview" which is more what I had in mind. I appreciate your reply and do agree with your final statement, though I'm not really sure on the idea of restricting the definition of language as you've described and personally have trouble finding such delineations.