Efficient Learning of Sparse Conditional Random Fields for Supervised Sequence Labelling

Conditional Random Fields (CRFs) constitute a popular and efficient approach for supervised sequence labelling. CRFs can cope with large description spaces and can integrate some form of structural dependency between labels. In this contribution, we address the issue of efficient feature selection for CRFs based on imposing sparsity through an L1 penalty. We first show how sparsity of the parameter set can be exploited to significantly speed up training and labelling. We then introduce coordinate descent parameter update schemes for CRFs with L1 regularization. We finally provide some empirical comparisons of the proposed approach with state-of-the-art CRF training strategies. In particular, it is shown that the proposed approach is able to take profit of the sparsity to speed up processing and hence potentially handle larger dimensional models

Learning the Structure of Variable-Order CRFs: a finite-state perspective

The computational complexity of linear-chain Conditional Random Fields (CRFs) makes it difficult to deal with very large label sets and long range dependencies. Such situations are not rare and arise when dealing with morphologically rich languages or joint labelling tasks. We extend here recent proposals to consider variable order CRFs. Using an effective finite-state representation of variable-length dependencies, we propose new ways to perform feature selection at large scale and report experimental results where we outperform strong baselines on a tagging task

Semiparametric estimation and testing in models of adverse selection, with an aplication to environmental regulation

We propose a flexible framework for estimating and testing structural models with adverse selection. This framework uses semiparametric methods for estimating consistently structural parameters of interest and for assesssing the results by testing procedures. We consider a problem of environmental regulation where firms are regulated through contracts. We show how to check parametric assumptions for the abatement cost function and test for neglected adverse selection. We then apply a semiparametric procedure for estimating models with adverse selection, that does not require to specify the distribution of the private information and avoids costly numerical procedures. The proposed framework can prove useful in a wide variety of problems where adverse selection can be present

‘The work is the same, but it’s different…’. Strategies facing the stigma of whore and victim among escort boys in France through the prism of gender and sexualities

Si les recherches en sciences sociales sur la prostitution se sont davantage intéressées aux femmes, et les théories qui en découlent aux rapports sociaux de sexe, cet article vise à montrer les particularités du maniement du stigmate et de ces deux facettes (victime et putain) touchant les escort-boys en France. À l'inverse des chercheur·e·s postulant une absence de stigmate parmi les hommes, nous tenterons de montrer la manière dont ces derniers mobilisent les représentations genrées inhérentes à la prostitution et les expériences de stigmatisation vécues liées aux sexualités comme ressources pour tracer des frontières symboliques afin d'y échapper. Ce faisant, nous montrerons que si les mécanismes de mise à distance du stigmate peuvent s'appuyer sur des articulations conceptuelles relatives au genre et aux sexualités, ce dernier est loin d'être absent de leurs vies, ce qui invite à une analyse plus approfondie des spécificités de ses manifestations.If social science research on prostitution has predominantly focused on women, and the resulting theories have centered on gender relations, this article aims to highlight the peculiarities of stigma management and the two facets (victim and whore) that affect escort boys in France. In contrast to researchers postulating an absence of stigma among men, we will attempt to demonstrate how they mobilize gendered representations inherent in prostitution and their experiences of stigmatization related to sexuality as resources to draw symbolic boundaries to escape it. In doing so, we will show that while the mechanisms for distancing themselves from stigma may draw on conceptual articulations related to gender and sexuality, the latter is far from absent from their lives, which calls for a more in-depth analysis of its specific manifestations.Grupo de investigación Antropología y Filosofía (SEJ-126). Universidad de Granada. Departamento de Antropología, Geografía e Historia. Universidad de Jaén. Departamento de Filosofía II. Universidad de Granada

Publier aujourd'hui une revue de sciences sociales

Le lecteur pourra prendre connaissance dans ces pages des interventions de la table ronde qui s’est tenue lors des journées d’étude organisées par Politix en vue de ce centième numéro. Ses participants ont, à partir de leur expérience propre, réfléchi aux opportunités et aux contraintes qui définissent actuellement l’édition de revues dans les sciences sociales

Breast cancer and quality of life: medical information extraction from health forums

International audienceInternet health forums are a rich textual resource with content generated through free exchanges among patients and, in certain cases, health professionals. We tackle the problem of retrieving clinically relevant information from such forums, with relevant topics being defined from clinical auto-questionnaires. Texts in forums are largely unstructured and noisy, calling for adapted preprocessing and query methods. We minimize the number of false negatives in queries by using a synonym tool to achieve query expansion of initial topic keywords. To avoid false positives, we propose a new measure based on a statistical comparison of frequent co-occurrences in a large reference corpus (Web) to keep only relevant expansions. Our work is motivated by a study of breast cancer patients' health-related quality of life (QoL). We consider topics defined from a breast-cancer specific QoL-questionnaire. We quantify and structure occurrences in posts of a specialized French forum and outline important future developments