Beginning with the pioneering work of Hobbs (1978), many practical approaches rely on the availability of syntactic surface structure by employing coindexing restrictions, salience criteria, and parallelism heuristics (e.g., Lappin and Leass 1994).
even the assumption of the availability of a unique syntactic description is unrealistic since, in general, parsing involves the solution of difficult problems like at-tachment ambiguities, role uncertainty, and the instantiation of empty categories.