Some additional grammar questions

This is a follow on to my earlier message regarding the grammar.

The current grammar allows aliases and declarations to occur throughout 
the source. 
Do the  aliases and declarations  apply to the entire source, or just the 
parts of the source that fall after them?

If they apply to the entire source, this suggests a need for two passes.
If they apply only to the rest of the file, this raises the question of a 
need for an unalias, for example.

I personally lean towards requiring the declarations and aliases at the 
start of the file, but at the moment
I am simply trying to understand the intent.

Stan Devitt