Open Challenges in Treebanking: Some Thoughts Based on the Copenhagen Dependency Treebanks

Proceedings of the Workshop on Annotation and Exploitation of Parallel Corpora AEPC 2010. Editors: Lars Ahrenberg, Jörg Tiedemann and Martin Volk. NEALT Proceedings Series, Vol. 10 (2010), 1-13. © 2010 The editors and contributors. Published by Northern European Association for Language Technology (NEALT) http://omilia.uio.no/nealt . Electronically published at Tartu University Library (Estonia) http://hdl.handle.net/10062/15893

The DTAG treebank tool. Annotating and querying treebanks and

DTAG is a versatile annotation tool that supports manual and semi-automatic annotation of a wide range of linguistic phenomena, including the annotation of syntax, discourse, coreference, morphology, and word alignments. It includes commands for editing general labeled graphs and graph alignments, comparing annotations, managing annotation tasks, and interfacing with a revision control system. Its visualization component can display graphs and alignments for entire texts in a compact format, with a highly flexible and configurable formatting scheme. It also provides a powerful search-replace mechanism with queries based on full first-order logic, which can be used to search for linguistic constructions and automatically apply graph transformations to collections of annotated graphs

A white paper

In this white paper, we review the theoretical evidence about the computational efficiency of dependency parsing and machine translation without the widely used, but linguistically questionable assumptions about projectivity and edge-factoring. On the basis of the heuristic local optimality parser proposed by (Buch-Kromann, 2006), we propose a common architecture for monolingual parsing, parallel parsing, and translation that does not make these assumptions. Finally, we describe the elementary repair operations in the model, and argue that the model is potentially interesting as a model of human translation

Hierarchy-based Partition Models: Using Classification Hierarchies to

We propose a novel machine learning technique that can be used to estimate probability distributions for categorical random variables that are equipped with a natural set of classification hierarchies, such as words equipped with word class hierarchies, wordnet hierarchies, and suffix and affix hierarchies. We evaluate the estimator on bigram language modelling with a hierarchy based on word suffixes, using English, Danish, and Finnish data from the Europarl corpus with training sets of up to 1–1.5 million words. The results show that the proposed estimator outperforms modified Kneser-Ney smoothing in terms of perplexity on unseen data. This suggests that important information is hidden in the classification hierarchies that we routinely use in computational linguistics, but that we are unable to utilize this information fully because our current statistical techniques are either based on simple counting models or designed for sample spaces with a distance metric, rather than sample spaces with a non-metric topology given by a classification hierarchy. Keywords: machine learning; categorical variables; classification hierarchies; language modelling; statistical estimatio

Smoothing survival densities in practice

Many nonparametric smoothing procedures consider independent identically distributed stochastic variables. There are also many important nonparametric smoothing applications where the data is more complicated. Survival data or filtered data, defined as following Aalen’s multiplicative hazard model and aggregated versions of this model, are considered. Aalen’s model based on counting process theory allows multiple left truncations and multiple right censoring to be present in the data. This type of filtering is omnipresent in biostatistical and demographical applications, where people can join a study, leave the study and perhaps join the study again. The estimation methodology is based on a recent class of local linear density estimators. A new stable bandwidth-selector is developed for these estimators. A data application to aggregated national mortality data is provided, where immigrations to and from the country correspond to respectively left truncation and right censoring. The aggregated mortality data study illustrates that the new practical density estimators provide an important extra element in the visual toolbox for understanding survival data

Double one-sided cross-validation of local linear hazards

This paper brings together the theory and practice of local linear kernel hazard estimation. Bandwidth selection is fully analysed, including Do-validation that is shown to have good practical and theoretical properties. Insight is provided into the choice of the weighting function in the local linear minimization and it is pointed out that classical weighting sometimes lacks stability. A new semiparametric hazard estimator transforming the survival data before smoothing is introduced and shown to have good practical properties

Bandwidth selection in marker dependent kernel hazard estimation

Practical estimation procedures for the local linear estimation of an unrestricted failure rate when more information is available than just time are developed. This extra information could be a covariate and this covariate could be a time series. Time dependent covariates are sometimes called markers, and failure rates are sometimes called hazards, intensities or mortalities. It is shown through simulations and a practical example that the fully local linear estimation procedure exhibits an excellent practical performance. Two different bandwidth selection procedures are developed. One is an adaptation of classical cross-validation, and the other one is indirect cross-validation. The simulation study concludes that classical cross-validation works well on continuous data while indirect cross-validation performs only marginally better. However, cross-validation breaks down in the practical data application to old-age mortality. Indirect cross-validation is thus shown to be superior when selecting a fully feasible estimation method for marker dependent hazard estimation

Further theoretical and practical insight to the do-validated bandwidth selector

Recent contributions to kernel smoothing show that the performance of cross-validated bandwidth selectors improves significantly from indirectness and that the recent do-validated method seems to provide the most practical alternative among these methods. In this paper we show step by step how classical cross-validation improves in theory, as well as in practice, from indirectness and that do-validated estimators improve in theory, but not in practice, from further indirectness. This paper therefore provides a strong support for the practical and theoretical properties of do-validated bandwidth selection. Do-validation is currently being introduced to survival analysis in a number of contexts and this paper provides evidence that this might be the immediate step forward