Varje varelse, varje skapelse, varje dröm som människan n˚agonsin drömt finns här. Ni formade dem i era drömmar och fabler och i era böcker, ni gav dem form och substans och ni trodde p˚a dem och gav dem makt att göra det och det ända tills de fick eget liv. Och sedan övergav ni dem. i Lundwall (1974, p. 114) ii This thesis investigates the expressive power and parsing complexity of the grammatical framework (gf), a formalism originally designed for displaying formal propositions and proofs in natural language. This is done by relating gf with two more well-known grammar formalisms; generalized contextfree grammar (gcfg), best seen as a framework for describing various grammar formalisms; and parallel multiple context-free grammar (pmcfg), an instance of gcfg. Since gf is a fairly new theory, some questions about expressivity and parsing complexity have until now not been answered; and these questions are the main focus of this thesis. The main result is that the important subclass context-free gf is equivalent to pmcfg, which has polynomial parsing complexity, and whose expressive power is fairly well known. Furthermore, we give a number of tabular parsing algorithms for pmcfg with polynomial complexity, by extending existing algorithms for context-free grammars. We suggest three possible extensions of gf/pmcfg, and discuss how the expressive power and parsing complexity are influenced. Finally, we discuss the parsing problem for unrestricted gf grammars, which is undecidable in general. We nevertheless describe a procedure for parsing grammars containing higher-order functions and dependent types.

EVALUATING GRAMMAR FORMALISMS FOR APPLICATIONS TO NATURAL LANGUAGE PROCESSING AND BIOLOGICAL SEQUENCE ANALYSIS David Chiang Supervisor: Aravind K. Joshi Grammars are gaining importance in statistical natural language processing and computational biology as a means of encoding theories and structuring algorithms. But one serious obstacle to applications of grammars is that formal language theory traditionally classifies grammars according to their weak generative capacity (WGC)---what sets of strings they generate---and tends to ignore strong generative capacity (SGC)---what sets of structural descriptions they generate---even though the latter is more relevant to applications.

We explore some properties of the synchronous formalism introduced in Dras (1999), showing that it handles an interaction, noted in Schuler (1999), between bridge and raising verbs which is problematic for synchronous TAG. We also show that it has greater formal power than synchronous TAG and discuss its computational complexity. 1.

The aim of this paper is to describe an approach to semantic representation in the Lexicalized Tree Adjoining Grammars (LTAG)[1] paradigm. We show how to use all the informations contained in the two representation structures provided by the LTAG formalism in order to provide a dependency graph.

We develop a set of new tabular parsing algorithms for Linear Indexed Grammars, including bottomup algorithms and Earley-like algorithms with and without the valid prefix property, creating a continuum in which one algorithm can in turn be derived from another. The output of these algorithms is a shared forest in the form of a context-free grammar that encodes all possible derivations for a given input string. 1 Introduction Tree Adjoining Grammars (TAG) [8] and Linear Indexed Grammars (LIG) [7] are extensions of Context Free Grammars (CFG). Tree adjoining grammars use trees instead of productions as primary representing structure and seems to be adequate to describe syntactic phenomena occurring in natural language, due to their extended domain of locality and to their ability for factoring recursion from the domain of dependencies. Linear indexed grammars associate a stack of indices with each non-terminal symbol, with the restriction that the indices stack of the head non-terminal ...

This paper describes the extension of the system DyALog to compile tabular parsers from Feature Tree Adjoining Grammars. The compilation process uses intermediary 2-stack automata to encode various parsing strategies and a dynamic programming interpretation to break automata derivations into tabulable fragments. 1.

: Vijay-Shanker and Weir have shown in [19] that Tree Adjoining Grammars and Combinatory Categorial Grammars can be transformed into equivalent Linear Indexed Grammars (LIGs) which can be recognized in O(n 6 ) time using a Cocke-Kasami-Younger style algorithm. This paper exhibits another recognition algorithm for LIGs, with the same upper-bound complexity, but whose average case behaves much better. This algorithm works in two steps: first a general context-free parsing algorithm (using the underlying context-free grammar) builds a shared parse forest, and second, the LIG properties are checked on this forest. This check is based upon the composition of simple relations and does not require any computation of symbol stacks. Key-words: context-sensitive parsing, ambiguity, parse tree, shared parse forest. (R'esum'e : tsvp) This research report is an extended version of [3].It benefits from discussions, especially with David Weir, and amends the original algorithm. E-mail: Pierre.Bo...

Contents 1Preface 5 2 Finite recognizers of languages 6 3 Some early proposals 19 4 Using non-deterministic machines 34 5 One level phonology 41 6 Optimality theory: first ideas 62 7 OTP: Primitive optimality theory 76 Lenient compositions: the proper treatment of OT? 86 9 Acquisition models 91 10 Exercises and speculations 113 1 Stabler - Lx 236 1999 A web page of readin gs: 236: some readings the beauty of finite state machines and related topics Yu 1997 Regular languages. In Rozenberg & Salomaa, eds. Handbook of Formal Languages, Volume 1. Perrin 1990 Finite automata. In J. Van Leuwen, Handbook of Theoretical Computer Science, Volume B. Salomaa 1973 Formal Languages. Sec 5 Hopcroft and Ullman 1979 Introduction to Automata Theory, Languages, and Comp

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We show how parsing of trees can be formalized in terms of the intersection of two tree languages. The focus is on weighted regular tree grammars and weighted tree adjoining grammars. Potential applications are discussed, such as parameter estimation across formalisms. 1