... simple com-binations of the frequencies f1. . . f4. Observa-tions of these frequencies therefore do not addany extra information, and the problem of fi nd-ing the weights of the target grammar ... Theoretical Evaluation of Estimation Methods for Data-Oriented ParsingWillem ZuidemaInstitute for Logic, Langu age and ComputationUniversity of AmsterdamPlantage Muidergracht ... and STSG formalism are de-scribed in detail elsewhere, for instance in (Bod,1998). The main difference with PCFGs is thatmultiple derivations, using elementary trees witha variety of sizes,...