At Clippers Tuesday, I’ll motivate a new approach to scope taking in combinatory categorial grammar and discuss progress and plans for implementing the approach (in collaboration with Jordan Needle, Carl Pollard, Simon Charlow and Dylan Bumford):
A long-standing puzzle in natural language semantics has been how to explain the exceptional scope behavior of indefinites. Charlow (2014) has recently shown that their exceptional scope behavior can be derived from a dynamic semantics treatment of indefinites, i.e. one where the function of indefinites is to introduce discourse referents into the evolving discourse context. To do so, he showed that (1) a monadic approach to dynamic semantics can be seamlessly integrated with Barker and Shan’s (2015) approach to scope taking in continuized grammars, and (2) once one does so, the exceptional scope of indefinites follows from the way the side effect of introducing a discourse referent survives the process of delimiting the scope of true quantifiers such as those expressed with ‘each’ and ‘every’.
To date, computationally implemented approaches to scope taking have not distinguished indefinites from true quantifiers in a way that accounts for their exceptional scope taking. Although Steedman (2011) has developed an account of indefinites’ exceptional scope taking by treating them as underspecified Skolem terms in a non-standard static semantics for Combinatory Categorial Grammar (CCG), this treatment has not been implemented in its full complexity. Moreover, as Barker and Shan point out, Steedman’s theory appears to be undergenerate by not allowing true quantifiers to take scope from medial positions.
Barker and Shan offer a brief sketch of how their approach might be implemented, including how lifting can be invoked lazily to ensure parsing terminates. In this talk, I will show how their approach can be seamlessly combined with Steedman’s CCG and extended to include the first prototype implementation of Charlow’s semantics of indefinites, thereby yielding an approach that improves upon scope taking in CCG while retaining many of its attractive computational properties.