-rule
to 
to is SEQUENCE [ [ :: ] association-name-list ]
-to or NO SEQUENCE [ [ :: ] association-name-list ]
association-name -to -rule
to 
to is object-name
-to or function-name
-to or / [ common-block-name ] /
XBNF
- A variable or COMMON block name may appear at most once
in a sequence-directive within any scoping unit.
BNFchapter
