The hierarchical phrase-based (HPB) model on the basis of a synchronous context-free grammar (SCFG) is prominent in solving global reorderings. However, the HPB model is inadequate to supervise the reordering process so that sometimes positions of different lexicons are switched due to the incorrect SCFG rules. In this paper, we consider the order of two lexicons as a classification problem and...

This thesis focus on the prediction of RNA secondary structure using stochastic context-free grammars (SCFG). The RNA secondary structure prediction problem consists of predicting a 2-dimensional structure from a 1-dimensional nucleotide sequence. The theory behind SCFG is explained and an overview of the research literature on various methods in the field of secondary structure prediction is g...

We present a sentence compression system based on synchronous context-free grammars (SCFG), following the successful noisy-channel approach of (Knight and Marcu, 2000). We define a headdriven Markovization formulation of SCFG deletion rules, which allows us to lexicalize probabilities of constituent deletions. We also use a robust approach for tree-to-tree alignment between arbitrary document-a...

Conventional wisdom dictates that synchronous context-free grammars (SCFGs) must be converted to Chomsky Normal Form (CNF) to ensure cubic time decoding. For arbitrary SCFGs, this is typically accomplished via the synchronous binarization technique of (Zhang et al., 2006). A drawback to this approach is that it inflates the constant factors associated with decoding, and thus the practical runni...

Pairwise stochastic context-free grammars ("Pair SCFGs") are powerful tools for finding conserved RNA structures, but unconstrained alignment to Pair SCFGs is prohibitively expensive. We develop versions of the Pair SCFG dynamic programming algorithms that can be conditioned on precomputed structures, significantly reducing the time complexity of alignment. We have implemented these algorithms ...

Context-sensitive grammars in which each rule is of the forln aZfl-~ (-*Tfl are acyclic if the associated context-free grammar with the rules Z ~ 3' is acyclic. The problem whether an intmt string is in the language generated by an acyclic context-sensitive grammar is NP-conlplete.

By introducing the Regular Membership Constraint, Gilles Pesant pioneered the idea of basing constraints on formal languages. The paper presented here is highly motivated by this work, taking the obvious next step, namely to investigate constraints based on grammars higher up in the Chomsky hierarchy. We devise an arc-consistency algorithm for context-free grammars, investigate when logic combi...

This article describes a probabilistic context free grammar approximation method for uniication grammars. In order to produce good results, the method is combined with an N best parsing extension to chart parsing. The rst part of the paper introduces the grammar approximation method, while the second part describes details of an eecient N-best packing and unpacking scheme for chart parsing.

In this paper, we review different context classification systems that have been used to define elements of context. Although existing classification systems cover various types of context, in the development of context aware applications, only a few types of context have been used. In this work, we aim to build a context classification model based on Activity Theory that provides a basis both ...

Learners that have better metacognition acquire knowledge faster than others who do not. If we had better models of such learning, we would be able to build a better metacognitive educational system. In this paper, we propose a computational model that uses a probabilistic context free grammar induction algorithm yielding metacognitive learning by acquiring deep features to assist future learni...