SDF is a syntax definition formalism used to describe context-free grammars of programming languages. The key principle underlying the design of SDF is declarative syntax definition, so that the user does not need to understand the underlying parsing algorithm, unlike other formalisms such as Yacc. This disambiguation method is able to handle common cases of operator precedence, but the current semantics of priorities fails to disambiguate some other less usual operator precedence that can be found in OCaml or Haskell languages. We propose a new semantics for SDF priorities that generalize the current approach. We describe a possible implementation of a GLR parse-table generator compliant to our semantics, and tested in the Spoofax Language Workbench.