[mmooss]

> But the phrase after the semicolon is at the same level as the initial phrase

If you mean my sentence in the GP, here's how I think it parses:

  A1 ; A2 . B

The two clauses in the first sentence, connected by the semicolon, are ~equal - but they are subparts of concept A. Concept B is separate and in a separate sentence. If I used no semicolon, I'd have three sentences and there would be no subparts, only

  A . B . C

[kranner]

That's how I had parsed it also. But to me adding another level in the outline sounded as if you had meant:

  A (B) . C

[mmooss]

Maybe I should have written,

  A(1;2) . B