We propose a formal characterization of variation in the syntactic realization of semantic arguments, using hierarchies of syntactic relations and thematic roles, and a mechanism of lexical inheritance to obtain emph{valency frames} from individual emph{linking types}. We embed the formalization in the new lexicalized, dependency-based grammar formalism of Topological Dependency Grammar (TDG) cite{rade-acl2001}. We account for arguments that can be alternatively realized as a NP or a PP, and model thematic role alternations. We also treat auxiliary constructions, where the correspondance between syntactic and semantic argumenthood is indirect
