Model Checking Parse Trees

Parse trees are fundamental syntactic structures in both computational linguistics and compilers construction. We argue in this paper that, in both fields, there are good incentives for model-checking sets of parse trees for some word according to a context-free grammar. We put forward the adequacy of propositional dynamic logic (PDL) on trees in these applications, and study as a sanity check the complexity of the corresponding model-checking problem: although complete for exponential time in the general case, we find natural restrictions on grammars for our applications and establish complexities ranging from nondeterministic polynomial time to polynomial space in the relevant cases.Comment: 21 + x page

Subject and object pronominal agreement in the southern Bantu languages: From a dynamic syntax perspective.

One of the most distinguishing aspects of the Bantu languages is the use of pronominal agreement markers. This thesis examines the nature of these agreement markers, focussing primarily the object marker, with Setswana being the primary language used for illustration due to the unusual feature of it allowing multiple object marker constructions. This thesis is comprised of seven chapters. The first chapter is the introduction and lays out the rest of the thesis with an explanation of what will be achieved in each chapter. The second chapter is an introduction to the Bantu languages and is primarily concerned with their structure, though there is also a discussion on the languages and the speakers themselves. The third chapter is an introduction to Setswana, the language primarily used in the thesis for illustration and examples. Setswana is a tone language and so this chapter includes a discussion on tone in the language, and in particular there is a section illustrating the grammatical effects of tone using the conjunctive/disjunctive distinction as identified by Creissels, 1996.1 The fourth chapter looks specifically at agreement in the Bantu languages, focussing on object marker agreement. It includes a discussion on the noun class system and then a comparison of two seminal works on the subject and object agreement markers in Bantu: Bresnan & Mchombo, 1987 and Demuth & Johnson, 1989.2 The fifth chapter is an introduction to Dynamic Syntax, the theory within which pronominal agreement is analysed in this thesis. The sixth chapter is the analysis of multiple object marker constructions in Setswana using the tools as provided by DS. The analysis involves invoking a notion of pragmatic inference combined with Local Adjunction. The seventh and final chapter is the conclusion which summarises the thesis and suggests possible avenues for further study or investigation

A proof system for finite trees

In this paper we introduce a description language for finite trees. Although we briefly note some of its intended applications, the main goal of the paper is to provide it with a sound and complete proof system. We do so using standard axioms from modal provability logic and modal logics of programs, and prove completeness by extending techniques due to Van Benthem and Meyer-Viol (1994) and Blackburn and Meyer-Viol (1994). We conclude with a proof of the EXPTIME-completeness of the satisfiability problem, and a discussion of issues related to complexity and theorem proving