Synchronous tree-adjoining grammars have been given two types of semantics: one based on bimorphisms and one based on synchronous derivations, in both of which the input and output trees are constructed synchronously. We introduce a third type of semantics that is based on unidirectional derivations. It derives output trees based on a given input tree and thus marks a first step towards conditi...

This paper presents a preprocessor based parsing system for Tree Adjoining Grammars. The preprocessor is used for two purposes: (1) to organize the data structures, (2) to reduce the runtime processing load so that the parser executes fast. A parallel parsing algorithm is presented that takes advantage of the preprocessor. The future goals of the proposed research are to achieve scalability and...

This paper describes the incremental generation of parse tables for the LRtype parsing of Tree Adjoining Languages (TALs). The algorithm presented handles modi cations to the input grammar by updating the parser generated so far. In this paper, a lazy generation of LR-type parsers for TALs is de ned in which parse tables are created by need while parsing. We then describe an incremental parser ...

LTAG is an appealing formalism for representing various phenomena (especially syntactic phenomena) in natural languages because of its linguistic and computational properties such as the Extended Domain of Locality, stronger generative capacity and lexicalized elementary trees. Because templates (i.e., elementary trees with the lexical items removed) in an LTAG grammar often share some common s...

In this paper a bidirectional parser for Lexicalized Tree Adjoining Grammars will be presented. The algorithm takes advantage of a peculiar characteristic of Lexicalized TAGs, i.e. that each elementary tree is associated with a lexical item, called its anchor. The algorithm employs a mixed strategy: it works bottom-up from the lexical anchors and then expands (partial) analyses making top-down ...

We use evolutionary algorithms to speed up a rather complex process, the tree adjoining grammars parsing. This improvement is due due to a linear matching function which compares the fitness of different individuals. Internally, derived trees are processed as tree-to-string representations. Moreover, we present some practical results and a post running analysis that may encourage the use of evo...

Grammars are core elements of many NLP applications. Grammars can be developed in two ways: built by hand or extracted from corpora. In this paper, we compare a handcrajted grammar with a Treebank grammar. We contend that recognizing substructures of the grammars' basic units is necessary tures and semantic information which are rarely represented in the corpora. lt would be ideal if we could c...

We define a decidable class of TAGs that is strongly equivalent to CFGs and is cubic-time parsable. This class serves to lexicalize CFGs in the same manner as the LC, FGs of Schabes and Waters but with considerably less restriction on the form of the grammars . The class provides a nornlal form for TAGs that generate local sets m rnuch the same way that regular g rammars provide a normal form f...

One approach to verification and validation of language processing systems includes the verification of system resources. In general, the grammar is a key resource in such systems. In this paper we discuss verification of lexicalized tree adjoining grammars (LTAGs) (Joshi and Schabes, 1997) as one instance of a system resource, and as one phase of a larger verification effort.