For instance, the dependency between the head of a noun phrase and the head of a reduced relative clause (the shares bought by John) is captured by the SD model, since shares and bought are both heads of the local trees that are combined to form the complex noun phrase.
in the SD model the probability of this dependency can only be estimated from occurrences of the same construction, since dependency relations are defined in terms of local trees and not in terms of the underlying predicate-argument struc-  ture.