name the common serving line of ottweiler station and saarbrücken hauptbahnhof ?
SELECT DISTINCT var_uri where brack_open dbr_Ottweiler_ attr_open Saar attr_close _station dbo_servingRailwayLine var_uri sep_dot dbr_Saarbrücken_Hauptbahnhof dbo_servingRailwayLine var_uri brack_close