A semantic encoding system?

[Rafal]

So in the absence of a key to decode it, this hypothesis implies the VMS will remain obscure no matter how much time we spend analyzing it’s structure. Am I wrong? Are there ways to translate a totally unknown and unrelated language without any rosetta stone?

Well, you may check my thread about the Rohonc Codex (note: this solution isn't universally accepted):
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In that case you don't have classical Rosetta stone (a text in two languages) but the text tells known stories and has illustrations suggesting the context. It's up to you if you call it "Rosetta stone" or not.

But yes, understanding unknown language, not similar to anything known, is hard. Take Etruscan for example ( You are not allowed to view links. Register or Login to view. ). We can even read it but still can understand only small fragments of it. I would say it's some general pattern - you don't just crack it and suddenly understand 100% of it but rather learn it in small steps, word by word, often through a long period.