1 ENTRY
2? (
2.1+ ,
2.1 %parameter-descr
2.1 %structure-union-descr
2.2 )

parameter-descr:

1+ 
1 attribute
1 *
1.1.0? 
1.1.0 ALIGNED
1.1.0 UNALIGNED
1.1? 
1.1 ASSIGNABLE
1.1 NONASSIGNABLE
1.1? 
1.1 CONNECTED
1.1 NONCONNECTED
1.1! BYADDR
1.1?
1.1? BYVALUE
1.2? OPTIONAL

structure-union-descr:

1 1
2+ 
2? attribute
3? OPTIONAL
4 ,
5+ 
5 level
5.1? attribute