Academic Publications

While (mainly) designed to answer users’ needs, search engines and recommendation systems do not necessarily guarantee the exposure of the data they store and index while it can be essential for information providers. A recent research direction so called “fair” exposure of documents tackles this problem in information retrieval. It has mainly been cast into a re-ranking problem with constraints and optimization functions. This paper presents the first steps toward a new framework for fair document exposure. This framework is based on document linking and document com- munity detection; communities are used to rank the documents to be retrieved according to an information need. In addition to the first step of this new framework, we present its potential through both a toy example and a few illustrative examples from the 2019 TREC Fair Ranking Track data set.

Search engines are based on models to index documents, match queries and documents and rank documents. Research in Information Retrieval (IR) aims at defining these models and their parameters in order to optimize the results. Using benchmark collections, it has been shown that there is not a best system configura- tion that works for any query, but rather that performance varies from one query to another. It would be interesting if a meta-system could decide which system config- uration should process a new query by learning from the context of previousqueries. This paper reports a deep analysis considering more than 80,000 search engine config- urations applied to 100 queries and the corresponding performance. The goal of the analysis is to identify which configuration responds best to a certain type of query. We considered two approaches to define query types: one is post-evaluation, based on query clustering according to the performance measured with Average Precision, while the second approach is pre-evaluation, using query features (including query difficulty predictors) to cluster queries. Globally, we identified two parameters that should be optimized: retrieving model and TrecQueryTags process. One could ex- pect such results as these two parameters are major components of IR process. However our work results in two main conclusions: 1/ based on post-evaluation approach, we found that retrieving model is the most influential parameter for easy queries while TrecQueryTags process is for hard queries; 2/ for pre-evaluation, current query fea- tures do not allow to cluster queries to identify differences in the influential parameters.

Word sense ambiguity has been identified as a cause of poor precision in information retrieval (IR) systems. Word sense disambiguation and discrimination methods have been defined to help systems choose which documents should be retrieved in relation to an ambiguous query. However, the only approaches that show a genuine benefit for word sense discrimination or disambiguation in IR are generally supervised ones. In this paper we propose a new unsupervised method that uses word sense discrimination in IR. The method we develop is based on spectral clustering and reorders an initially retrieved doc- ument list by boosting documents that are semantically similar to the target query. For several TREC ad hoc collections we show that our method is useful in the case of queries which contain ambiguous terms. We are interested in improving the level of precision after 5, 10 and 30 retrieved documents (P@5, P@10, P@30) respectively. We show that precision can be improved by 8% above current state-of-the-art baselines. We also focus on poor performing queries.

Reviews on web resources (e.g. courses, movies) become increasingly exploited in text analysis tasks (e.g. opinion detection, controversy detection). This paper investigates contradiction intensity in reviews exploiting different features such as variation of ratings and variation of polarities around specific entities (e.g. aspects, topics). Firstly, aspects are identified according to the distributions of the emotional terms in the vicinity of the most frequent nouns in the reviews collection. Secondly, the polarity of each review segment containing an aspect is estimated. Only resources containing these aspects with opposite polarities are considered. Finally, some features are evaluated, using feature selection algorithms, to determine their impact on the effectiveness of contradiction intensity detection. The selected features are used to learn some state-of- the-art learning approaches. The experiments are conducted on the Massive Open Online Courses data set containing 2244 courses and their 73,873 reviews, collected from coursera.org. Results showed that variation of ratings, variation of polarities, and reviews quantity are the best predictors of contradiction intensity. Also, J48 was the most effective learning approach for this type of classification.

Natural Language Processing (NLP) of textual data is usually broken down into a sequence of several subtasks, where the output of one the subtasks becomes the input to the following one, which constitutes an NLP pipeline. Many third-party NLP tools are currently available, each performing distinct NLP subtasks. However, it is difficult to integrate several NLP toolkits into a pipeline due to many problems, including different input/output representations or formats, distinct programming languages, and tokenization issues. This paper presents DeepNLPF, a framework that enables easy integration of third-party NLP tools, allowing the user to preprocess natural language texts at lexical, syntactic, and semantic levels. The proposed framework also provides an API for complete pipeline customization including the definition of input/output formats, integration plugin management, transparent multiprocessing execution strategies, corpus-level statistics, and database persistence. Furthermore, the DeepNLPF user-friendly GUI allows its use even by a non-expert NLP user. We conducted runtime performance analysis showing that DeepNLPF not only easily integrates existent NLP toolkits but also reduces significant runtime processing compared to executing the same NLP pipeline in a sequential manner.

Deep Learning is more and more used in NLP tasks, such as in relation classification of texts. This paper assesses the impact of syntactic dependencies in this task at two levels. The first level concerns the generic Word Embedding (WE) as input of the classification model, the second level concerns the corpus whose relations have to be classified. In this paper, two classification models are studied, the first one is based on a CNN using a generic WE and does not take into account the dependencies of the corpus to be treated, and the second one is based on a compositional WE combining a generic WE with syntactical annotations of this corpus to classify. The impact of dependencies in relation classification is estimated using two different WE. The first one is essentially lexical and trained on the Wikipedia corpus in English, while the second one is also syntactical, trained on the same previously annotated corpus with syntactical dependencies. The two classification models are evaluated on the SemEval 2010 reference corpus using these two generic WE. The experiments show the importance of taking dependencies into account at different levels in the relation classification.

In this paper, we look at how social media, in particular Twitter, are used to trigger, propagate and regulate opinions, and social controversies. Social media platforms are displacing the mainstream media and traditional sources of knowledge by facilitating the propagation of ideologies and causes championed by different groups of people. This results in pressures being brought to bear on institutions in the real world which are forced to make hasty decisions based on social media campaigns. The new forms of activism and the public arena enabled by social media platforms have also facilitated the propagation of so-called “post-truth” and “alternative facts” that obfuscate the traditional processes of knowledge elaboration which took decades to arrive at. This poses serious challenges for Knowledge Organization systems (KOs) that the KO community needs to find ways to address.

Analysis of opinions (reviews) generated by users becomes increasingly exploited by a variety of applications. It allows to follow the evolution of the opinions or to carry out investigations on web resource (e.g. courses, movies, products). The detection of contradictory opinions is an important task to evaluate the latter. This paper focuses on the problem of detecting and estimating contradiction intensity based on the sentiment analysis around specific aspects of a resource. Firstly, certain aspects are identified, according to the distributions of the emotional terms in the vicinity of the most frequent names in the whole of the reviews. Secondly, the polarity of each review segment containing an aspect is estimated using the state-of-the-art approach SentiNeuron. Then, only the resources containing these aspects with opposite polarities (positive, negative) are considered. Thirdly, a measure of the intensity of the contradiction is introduced. It is based on the joint dispersion of the polarity and the rating of the reviews containing the aspects within each resource. The evaluation of the proposed approach is conducted on the Massive Open Online Courses collection containing 2244 courses and their 73,873 reviews, collected from Coursera. The results revealed the effectiveness of the proposed approach to detect and quantify contradictions.

The aim of this research is to investigate how social media mediate social controversies in the public arena. For that, we will use the CLEF MC2 corpus of microblogs that captured long term political and cultural controversies in order to follow the birth and development of controversies across time and pinpoint the increasing role that social media play in their propagation, regulation and resolution.

This paper investigates an approach for estimating the effectiveness of any IR system. The approach is based on the idea that a set of documents retrieved for a specific query is highly relevant if there are only a small number of predominant topics in the retrieved documents. The proposed approach is to determine the topic probability distribution of each document offline, using Latent Dirichlet Allocation. Then, for a retrieved set of documents, a set of probability distribution shape descriptors, namely the skewness and the kurtosis, are used to compute a score based on the shape of the cumulative topic distribution of the respective set of documents. The proposed model is termed DeShaTo, which is short for Describing the Shape of cumulative Topic distributions. In this work, DeShaTo is used to rank retrieval systems without relevance judgments. In most cases, the empirical results are better than the state of the art approach. Compared to other approaches, DeShaTo works independently for each system. Therefore, it remains reliable even when there are less systems to be ranked by relevance.

This paper presents MyBestQuery, a serious game designed to collect query reformulations from players. Query reformulation is a hot topic in information retrieval and covers many aspects. One of them is query reformulation analysis which is based on users’ session. It can be used to understand user’s intent or to measure his satisfaction with regards to the results he obtained when querying the search engine. Automatic query reformulation is another aspect of query reformulation. It automatically expands the initial user’s query in order to improve the quality of the retrieved document set. This mechanism relies on document analysis but could also benefit from manually reformulated query analysis. Web search engines collect millions of search sessions and possible query reformulations. As academics, this information is hardly accessible for us. MyBestQuery is designed as a serious game in order to collect various possible reformulation users suggest. The more long-term objective of this work is to analyse the humanly produced query reformulation in order to both analyse manual query reformulation and compare them with the automatically produced reformulations. Preliminary results are reported in this paper.

Résumé :

MyBestQuery est un jeu sérieux qui collecte des éléments sur les requêtes soumises à un moteur de recherche: (i) la prédiction de la difficulté de la requête par le joueur (ii) des raisons possibles expliquant cette difficulté (iii) des propositions de reformulation.

Abstract:

MyBestQuery is a serious game designed to collect items from queries submitted to a search engine: (i) the query difficulty prediction (ii) the possible reasons for this difficulty (iii) other query formulations.

Résumé :

Les moteurs de recherche d’information (RI) retrouvent des réponses quelle que soit la requête, mais certaines requêtes sont difficiles (le système n’obtient pas de bonne performance en termes de mesure de RI). Pour les requêtes difficiles, des traitements ad-hoc doivent être appliqués. Prédire qu’une requête est difficile est donc crucial et différents prédicteurs ont été proposés. Dans cet articlenous étudions la variété de l’information captée par les prédicteurs existants et donc leur non redondance. Par ailleurs, nous montrons que les corrélations entre les prédicteurs et les performance des systèmes donnent peu d’espoir sur la capacité de ces prédicteurs à être réellement efficaces. Enfin, nous étudions la capacité des prédicteurs à prédire les classes de difficulté des requêtes en nous appuyant sur une variété de méthodes exploratoires et d’apprentissage. Nous montrons que malgré les (faibles) corrélations observées avec les mesures de performance, les prédicteurs actuels conduisent à des performances de prédiction variables et sont donc difficilement utilisables dans une application concrète de RI.

Abstract:

Search engines found answers whatever the user query is, but some queries are more difficult than others for the system. For difficult queries, adhoc treatments must be applied. Predicting query difficulty is crucial and different predictors have been proposed. In this paper, we revisit these predictors. First we check the non statistical redundancy of predictors. Then, we show that the correlation between the values of predictors and system performance gives little hope on the ability of these predictors to be effective. Finally, we study the ability of predictors to predict the classes of difficulty by relying on a variety of exploratory and learning methods. We show that despite the (low) correlation with performance measures, current predictors are not robust enough to be used in practical IR applications.

It has been shown that there is not a best information retrieval system configuration which would work for any query, but rather that performance can vary from one query to another. It would be interesting if a meta-system could decide which system should process a new query by learning from the context of previously submitted queries. This paper reports a deep analysis considering more than 80,000 search engine configura- tions applied to 100 queries and the corresponding performance. The goal of the analysis is to identify which search engine configuration responds best to a certain type of query. We considered two approaches to define query types: one is based on query clustering according to the query performance (their difficulty), while the other approach uses various query features (including query difficulty predictors) to cluster queries. We identified two parameters that should be optimized first. An important outcome is that we could not obtain strong conclusive results; considering the large number of systems and methods we used, this result could lead to the conclusion that current query features does not fit the optimizing problem.

Résumé :

Si l’expansion de requête automatique améliore en moyenne la qualité de recherche, elle peut la dégrader pour certaines requêtes. Ainsi, certains travaux s’intéressent à développer des approches sélectives qui choisissent la fonction de recherche ou d’expansion en fonction des requêtes. La plupart des approches sélectives utilisent un processus d’apprentissage sur des caractéristiques de requêtes passées et sur les performances obtenues. Cet article présente une nouvelle méthode d’expansion sélective qui se base sur des prédicteurs de difficulté des requêtes, prédicteurs linguistiques et statistiques. Le modèle de décision est appris par un SVM. Nous montrons l’efficacité de la méthode sur des collections TREC standards. Les modèles appris ont classé les requêtes de test avec plus de 90% d’exactitude. Par ailleurs, la MAP est améliorée de plus de 11%, comparée à des méthodes non sélectives.

Abstract:

Query expansion (QE) improves the retrieval quality in average, even though it can dramatically decrease performance for certain queries. This observation drives the trend to suggest selective approaches that aim at choosing the best function to apply for each query. Most of selective approaches use a learning process on past query features and results. This paper presents a new selective QE method that relies on query difficulty predictors. The method combines statistically and linguistically based predictors. The QE method is learned by a SVM. We demonstrate the efficiency of the proposed method on a number of standard TREC benchmarks. The supervised learning models have performed the query classification with more than 90% accuracy on the test collection. Our approach improves MAP by more than 11%, compared to the non selective methods.

Résumé :

La performance d’un Système de Recherche d’Information (SRI) est étroite- ment liée à la requête. Les requêtes pour lesquelles les SRI échouent sont appelées dans la littérature des « requêtes difficiles ». L’étude présentée dans cet article vise à ana- lyser, adapater et combiner plusieurs prédicteurs de difficulté de requêtes. Nous avons considéré trois prédicteurs: un lié à l’ambiguïté des termes, un basé sur la fréquence des termes et une mesure de répartition des résultats. L’évaluation de la prédiction est basée sur la corrélation entre la difficulté prédite et la performance réelle des SRI. Nous montrons que la combinaison de ces prédicteurs donne de bons résultats. Le cadre d’évaluation est celui des collections TREC7 et TREC8 adhoc.

Abstract:

The performance of an Information Retrieval System (IRS) is closely related to the query. The queries that lead to retrieval failure are referenced in the literature as “difficult queries”. This study aims at analysing, adapting and combining several difficulty predictors. The evaluation of the prediction is based on the correla- tion between the predicted difficulty and the IRS performance. As predictors, we have considered an ambiguity predictor, the IDF measure and a score distribution measure. We show that combining the proposed predictors, produce good results. The evaluation framework consists in the TREC7 and TREC8 ahdoc collections.