I m really no expert and attempting to come up to speed. But...It strikes me that LLM s are a subtle combination of knowing the language and knowing some facts. If one were making a chatbot for helping (say) people understand their tax returns then you d want a base LLM that understood language and then add domain specific knowledge via RAG. So yes to knowing that Thursday comes after Wednesday; no to knowing how high Everest is; and questions regarding income tax have to reference the RAG. Is this correct?So are there stock thin models for doing this? Is it better to train your own?