I thought it was mandatory to keep the annotations in the rules here? It isn't the case? For instance, in some old Tiger.sdf modules, I read: module Tiger-Statements imports Tiger-Expressions exports context-free syntax LValue ":=" Exp -> Exp {cons("Assign")} "Label" IntConst Exp -> Exp {cons("ExpLabel")} "(" {Exp ";"}* ")" -> Exp {cons("Seq")} "if" Exp "then" Exp "else" Exp -> Exp {cons("If")} "if" Exp "then" Exp -> Exp {cons("IfThen")} "while" Exp "do" Exp -> Exp {cons("While")} "repeat" Exp "whilst" Exp -> Exp {cons("DoWhile")} "for" Var ":=" Exp "to" Exp "do" Exp -> Exp {cons("For")} "break" -> Exp {cons("Break")} "for" Var ":=" Exp "to" Exp "in" Exp "do" Exp -> Exp {cons("ForStride")} "[" {LValue ","}* "]" ":=" "[" {Exp ","}* "]" -> Exp {cons("ParAssign")} "label" Id -> Exp {cons("Label")} "goto" Id -> Exp {cons("Goto")} "if" Exp "goto" Id -> Exp {cons("IfGoto")} %% "(" {Exp "||"}2+ ")" -> Exp {cons("Par")} context-free priorities Exp "|" Exp -> Exp {left,cons("Or")} "if" Exp "then" Exp "else" Exp -> Exp {cons("If")} "if" Exp "then" Exp -> Exp {cons("If")} "while" Exp "do" Exp -> Exp {cons("While")} "repeat" Exp "whilst" Exp -> Exp {cons("DoWhile")} "for" Var ":=" Exp "to" Exp "do" Exp -> Exp {cons("For")} } Note that they preciously kept the annotations.