Modeling syntactic constraints on anaphoric binding

Syntactic constraints on antecedent-anaphor relations can be stated within the theory of Lexical Functional Grammar (henceforth LFG) through the use of functional uncertainty (Kaplan and Maxwell 1988; Halvorsen and Kaplan 1988; Ksplan and Zaenen 1989). In the following, we summarize the general characteristics of syntactic constraints on anaphoric binding. Next, we describe a variation of functional uncertainty called ins ide-out functional uncer ta inty and show how it can be used to model anaphoric binding. Finally, we discuss some binding constraints claimed to hold in natural language to exemplify the mechanism. We limit our a t tent ion throughout to coreference possibilities between definite antecedents and anaphoric elements and ignore interactions with quantifiers. We also limit our discussion to intrasententiM relations. 1 G e n e r a l c h a r a c t e r i s t i c s o f s y n t a c t i c c o n s t r a i n t s o n a n a p h o r i c b i n d i n g The relation between an anaphor and its antecedent is semantic in nature. In the simple cases that we limit our at tention to here, the two are coreferent. 1 This semantic relation is subject to syntactic constraints, however, and it is the s ta tement of these constraints that we focus on. In the LFG approach to these constraints proposed in Bresnan et al. (1985), 2 binding conditions are stated as conditions on fs t ructure configurations rather than conditions on c-structures. Two kinds of syntactic fac1This is of course not always the case. Reciprocals and b ind ing by quant i f i ed N P ' s are two well-known cases in which the s e m a n t i c re la t ion is more compl ica ted . 2For a s u m m a r y of the views in B r e s n a n et al. (1985), see Sells (1985). tots are shown to influence anaphoric binding possibilities: the grammatical function of the potential antecedent (in particular whether or not it is a subject) and the characteristics of the syntactic domain in which the potential antecedent and the anaphor are found (for example, whether that domain is tensed or whether it has a subject). In Bresnan et al. (1985), anaphors are consequently annotated for both domain and antecedent constraints. Some constraints are stated in positive terms: the antecedent must be tbund within a particular domain or have a particular function. In other cases the constraints are negative: the antecedent and the anaphor cannot both be part of a particular domain, or the antecedent cannot bear a particular grammatical function. Under such negative conditions, the a naphor is dis joint in reference from its antecedent. 2 M o d e l i n g b i n d i n g c o n s t r a i n t s w i t h f u n c t i o n a l u n c e r t a i n t y F-structure relations are in some cases not characterizable as a finite disjunction over paths: for example, dependencies between ~fillers' and 'gaps' in, for example, relative clauses and whquestions. Functional uncer ta inty was developed for the analysis of such dependencies. Kaplan and Maxwell (1988) and Kaplan and Zaenen (1989) develop a formal specification of relations involving disjunction over paths by allowing the argument position of functionM equations to denote a set of strings. Suppose (t is a (possibly infinite) set of symbol strings; then (1) ( f a ) = v holds if and only if a. f = v a n d e 6 a , or b. ( ( f s) Surf(s ,a)) = v for some symbol s, where Surf(s, a ) is the set of suffix strings y such that sy 6 a.