  This paper describes a method for estimating conditional probability
distributions over the parses of ``unification-based'' grammars which can
utilize auxiliary distributions that are estimated by other means. We show how
this can be used to incorporate information about lexical selectional
preferences gathered from other sources into Stochastic ``Unification-based''
Grammars (SUBGs). While we apply this estimator to a Stochastic
Lexical-Functional Grammar, the method is general, and should be applicable to
stochastic versions of HPSGs, categorial grammars and transformational
grammars.
