Lexicalization and Grammar Development

In this paper we present a fully lexicalized grammar formalism as a particularly attractive framework for the specification of natural language grammars. We discuss in detail Feature-based, Lexicalized Tree Adjoining Grammars (FB-LTAGs), a representative of the class of lexicalized grammars. We illustrate the advantages of lexicalized grammars in various contexts of natural language processing, ranging from wide-coverage grammar development to parsing and machine translation. We also present a method for compact and efficient representation of lexicalized trees.Comment: ps file. English w/ German abstract. 10 page

Adjunct hexagonal array token Petri nets and hexagonal picture languages

Adjunct Hexagonal Array Token Petri Net Structures (AHPN) are re- cently introduced hexagonal picture generating devices which extended the Hexag- onal Array Token Petri Net Structures . In this paper we consider AHPN model along with a control feature called inhibitor arcs and compare it with some ex- pressive hexagonal picture generating and recognizing models with respect to the generating power

LFG without C-structures

We explore the use of two dependency parsers, Malt and MST, in a Lexical Functional Grammar parsing pipeline. We compare this to the traditional LFG parsing pipeline which uses constituency parsers. We train the dependency parsers not on classical LFG f-structures but rather on modified dependency-tree versions of these in which all words in the input sentence are represented and multiple heads are removed. For the purposes of comparison, we also modify the existing CFG-based LFG parsing pipeline so that these "LFG-inspired" dependency trees are produced. We find that the differences in parsing accuracy over the various parsing architectures is small

Factoring Predicate Argument and Scope Semantics : underspecified Semantics with LTAG

In this paper we propose a compositional semantics for lexicalized tree-adjoining grammar (LTAG). Tree-local multicomponent derivations allow separation of the semantic contribution of a lexical item into one component contributing to the predicate argument structure and a second component contributing to scope semantics. Based on this idea a syntax-semantics interface is presented where the compositional semantics depends only on the derivation structure. It is shown that the derivation structure (and indirectly the locality of derivations) allows an appropriate amount of underspecification. This is illustrated by investigating underspecified representations for quantifier scope ambiguities and related phenomena such as adjunct scope and island constraints

"Natural relations" : a note on X'-structure

With the rise of minimalism, many concepts related to the geometrical relations of phrase structure held fast to in earlier approaches have been reconsidered. This article deals with distinguishing (relational and technical) properties of specifiers and adjuncts in a Bare Phrase Structure framework (X'-Theory). I extend specific aspects of X-structure relevant to the discussion of specifiers vs. adjuncts. I argue that unique specifiers can be derived from the system and that adjunction, possibly multiple, results from Direct Merge only. The final product is a series of relationships in line with recent thoughts and minimalist premises, but formally more similar to earlier conceptions of the X'-schema. I address conceptual, empirical and theoretical arguments against multiple specifiers and related issues next, that is beyond the predictions immediately following from the tripartitional view of clause structure proposed in Grohmann (2000). After laying out my motivations to critically consider the issue, I present a set of data that casts serious doubt over the justifications offered to replace Agr with v as the accusative casemarker. Having conceptual and empirical back-up, I then tackle the theoretical validity of specifiers, and ways to distinguish unique specifiers from (multiple) adjuncts. I introduce a version of Bare Phrase Structure that does so, yet keeps the spirit of defining structural identification over relational rather than categorial properties

The syntax of discourse functions in Greek: a non-configurational approach

This thesis offers an account of the syntactic properties of Focus-movement, Topicalisation and Clitic Left Dislocation (CLLD) in Greek. As these phenomena are central to discussions of the syntax-discourse interface, a significant part of this study pursues the question of the representation of the discourse functions of topic and focus and their relation to syntax.For the most part, the literature on the syntax of Focus-movement, Topicalisation and CLLD advocates that focus and topic are encoded in the Phrase Structure by distinct Func¬ tional Projections: Focus Phrase (FP) and Topic Phrase (TP). Foci and topics move to the Specifier of the relevant Projection to check their discourse features. The term Discourse Configurational Languages has been recently coined for languages that encode focus and topic through Phrase Structure configurations.With respect to the syntactic properties of the relevant structures, the Discourse Configurational approach assumes that Focus-movement, Topicalisation and CLLD instantiate three distinct syntactic operations; A-bar-movement, A-movement and base-generation respectively. This complex syntax enables a simple view of the syntax-discourse interface; there is an isomorphic relation between syntax and discourse, as each discourse function is associated with a distinct syntactic operation. Further, focus and topic are treated as syntactic features, specifying heads of Functional Projections.This thesis, in contrast, argues for a non-configurational approach. It shows that the claim that Focus-movement and Topicalisation instantiate A-bar-movement and A-movement respectively is based on insufficient evidence. This claim is motivated by the absence of weak crossover effects in Topicalisation and their presence in Focus-movement. However, this study argues that the weak crossover effect is not a valid diagnostic of the A/A-bar distinction, since some cases of Wh-questions, the prototypical instance of A-bar movement, do not give rise to weak crossover effect. Further, in the Discourse Configurational approach, CLLD is treated as an instance of base-generation rather than movement, because it does not license parasitic gaps. In this thesis, CLLD is analysed as adjunct extraction and it is shown that the unavailability of parasitic gaps is a general property of adjunct extraction. Further, this study demonstrates that Focus-movement, Topicalisation and CLLD exhibit the same syntactic properties and instantiate the same extraction mechanism. Thus, they are given a unified syntactic treatment.The argument that Focus-movement, Topicalisation and CLLD share the same syntax has implications for the architecture of the discourse-syntax interface. Unlike the Discourse Configurational approach, this syntactic analysis implies a non-isomorphic relation between syntax and discourse, as a single syntactic structure corresponds to more than one discourse function. Thus, the syntax of discourse constructions is independent of the discourse func¬ tions encoded. It is argued that the discourse evidence does not justify the incorporation of discourse functions in Phrase Structure or their treatment as syntactic features. Rather, focus and topic should be represented at a distinct level, independent of syntax, Information Structure.The analysis is couched in the framework of Head-driven Phrase Structure Grammar. The syntactic properties of extractions in Greek are readily captured by the HPSG mechanism of Unbounded Dependencies. The multidimensional nature of HPSG signs allows for the representation of discourse functions and a flexible mapping between syntax and discourse

Treebank-based acquisition of a Chinese lexical-functional grammar

Scaling wide-coverage, constraint-based grammars such as Lexical-Functional Grammars (LFG) (Kaplan and Bresnan, 1982; Bresnan, 2001) or Head-Driven Phrase Structure Grammars (HPSG) (Pollard and Sag, 1994) from fragments to naturally occurring unrestricted text is knowledge-intensive, time-consuming and (often prohibitively) expensive. A number of researchers have recently presented methods to automatically acquire wide-coverage, probabilistic constraint-based grammatical resources from treebanks (Cahill et al., 2002, Cahill et al., 2003; Cahill et al., 2004; Miyao et al., 2003; Miyao et al., 2004; Hockenmaier and Steedman, 2002; Hockenmaier, 2003), addressing the knowledge acquisition bottleneck in constraint-based grammar development. Research to date has concentrated on English and German. In this paper we report on an experiment to induce wide-coverage, probabilistic LFG grammatical and lexical resources for Chinese from the Penn Chinese Treebank (CTB) (Xue et al., 2002) based on an automatic f-structure annotation algorithm. Currently 96.751% of the CTB trees receive a single, covering and connected f-structure, 0.112% do not receive an f-structure due to feature clashes, while 3.137% are associated with multiple f-structure fragments. From the f-structure-annotated CTB we extract a total of 12975 lexical entries with 20 distinct subcategorisation frame types. Of these 3436 are verbal entries with a total of 11 different frame types. We extract a number of PCFG-based LFG approximations. Currently our best automatically induced grammars achieve an f-score of 81.57% against the trees in unseen articles 301-325; 86.06% f-score (all grammatical functions) and 73.98% (preds-only) against the dependencies derived from the f-structures automatically generated for the original trees in 301-325 and 82.79% (all grammatical functions) and 67.74% (preds-only) against the dependencies derived from the manually annotated gold-standard f-structures for 50 trees randomly selected from articles 301-325

Linguistics and some aspects of its underlying dynamics

In recent years, central components of a new approach to linguistics, the Minimalist Program (MP) have come closer to physics. Features of the Minimalist Program, such as the unconstrained nature of recursive Merge, the operation of the Labeling Algorithm that only operates at the interface of Narrow Syntax with the Conceptual-Intentional and the Sensory-Motor interfaces, the difference between pronounced and un-pronounced copies of elements in a sentence and the build-up of the Fibonacci sequence in the syntactic derivation of sentence structures, are directly accessible to representation in terms of algebraic formalism. Although in our scheme linguistic structures are classical ones, we find that an interesting and productive isomorphism can be established between the MP structure, algebraic structures and many-body field theory opening new avenues of inquiry on the dynamics underlying some central aspects of linguistics.Comment: 17 page