Modularity and Soft Constraints: A study of conflict resolution in grammar (2005)

This thesis advocates a modular and parallel grammar architecture with declarative constraints on the syntactic, semantic, prosodic, and pragmatic structures which are derived in parallel while mutually constraining one another as proposed by Jackendoff (1997, 2002). The main claim of this thesis is that because of the many conflicting requirements among modules, the interfaces cannot employ crisp constraints. Instead, a soft-constraint satisfaction approach is required. We also argue that simply violable constraints are insufficient to account for certain linguistic phenomena; there is need for graded constraints that allow for degrees of violation. The dissertation first provides a review of different conceptions of gradience in linguistics followed by a review of the concept of modularity in cognitive science and linguistics. The problem of conflicting requirements in the field of Constraint Logic Programming (CLP) has led to various soft constraint satisfaction approaches. The dissertation then presents a generalized theory of soft constraint satisfaction (Bistarelli, 2001) from the CLP literature. The dissertation then presents a case study of graded constraints showing that such constraints exist at interfaces and that they can exhibit degrees of violation. Another case study shows that the modular parallel architecture allows for simpler modules and is able to capture generalizations better. We then conclude by showing how the generalized theory of soft-constraint satisfaction can be incorporated within grammar without disrupting the existing explanatory power of constraintbased theories such as LOT (Keller, 2000) and HPSG (Pollard and Sag, 1994).