anchor.diff:  macroName :
       | 'MODULE-COMPLIANCE'
       | 'OBJECT-GROUP'
  -    | 'MODULE-IDENTITY'
       | 'OBJECT-IDENTITY'
       | 'NOTIFICATION-TYPE'
       | 'NOTIFICATION-GROUP'
  
positive.code:     'IMPLIED'? type
      ;
  
  textualConventionAssignement :
      '::=' 'TEXTUAL-CONVENTION' (complexAttribut ','*)+
      ;
  
negative.code:      | textualConventionAssignement
       | objectTypeAssignement
       | trapTypeAssignement
       | moduleIdentityAssignement
       | macroAssignement
       ;
  
  