5.7 Complete Definition of an Abstract Syntax

The complete definition of an abstract syntax is given by a name (for the defined formalism) and a list of declaration.

program     -->   "abstract" "syntax" "of" id "is"
                     declaration*
                  "end" [id] ";"
declaration -->   operator | inclusion | union | line

The last identifier is optional. If present it must be equal to the first one. However, the parser does not check this constraint.