5 research outputs found
Filtrage et agrégation d'informations vitales relatives à des entités
Nowadays, knowledge bases such as Wikipedia and DBpedia are the main sources to access information on a wide variety of entities (an entity is a thing that can be distinctly identified such a person, an organization, a product, an event, etc.). However, the update of these sources with new information related to a given entity is done manually by contributors with a significant latency time particularly if that entity is not popular. A system that analyzes documents when published on the Web to filter important information about entities will probably accelerate the update of these knowledge bases. In this thesis, we are interested in filtering timely and relevant information, called vital information, concerning the entities. We aim at answering the following two issues: (1) How to detect if a document is vital (i.e., it provides timely relevant information) to an entity? and (2) How to extract vital information from these documents to build a temporal summary about the entity that can be seen as a reference for updating the corresponding knowledge base entry?Regarding the first issue, we proposed two methods. The first proposal is fully supervised. It is based on a vitality language model. The second proposal measures the freshness of temporal expressions in a document to decide its vitality. Concerning the second issue, we proposed a method that selects the sentences based on the presence of triggers words automatically retrieved from the knowledge already represented in the knowledge base (such as the description of similar entities).We carried out our experiments on the TREC Stream corpus 2013 and 2014 with 1.2 billion documents and different types of entities (persons, organizations, facilities and events). For vital documents filtering approaches, we conducted our experiments in the context of the task "knowledge Base Acceleration (KBA)" for the years 2013 and 2014. Our method based on leveraging the temporal expressions in the document obtained good results outperforming the best participant system in the task KBA 2013. In addition, we showed the importance of our generated temporal summaries to accelerate the update of knowledge bases.Aujourd'hui, les bases de connaissances telles que Wikipedia et DBpedia représentent les sources principales pour accéder aux informations disponibles sur une grande variété d'entités (une entité est une chose qui peut être distinctement identifiée par exemple une personne, une organisation, un produit, un événement, etc.). Cependant, la mise à jour de ces sources avec des informations nouvelles en rapport avec une entité donnée se fait manuellement par des contributeurs et avec un temps de latence important en particulier si cette entité n'est pas populaire. Concevoir un système qui analyse les documents dès leur publication sur le Web pour filtrer les informations importantes relatives à des entités pourra sans doute accélérer la mise à jour de ces bases de connaissances. Dans cette thèse, nous nous intéressons au filtrage d'informations pertinentes et nouvelles, appelées vitales, relatives à des entités. Ces travaux rentrent dans le cadre de la recherche d'information mais visent aussi à enrichir les techniques d'ingénierie de connaissances en aidant à la sélection des informations à traiter. Nous souhaitons répondre principalement aux deux problématiques suivantes: (1) Comment détecter si un document est vital (c.à .d qu'il apporte une information pertinente et nouvelle) par rapport à une entité donnée? et (2) Comment extraire les informations vitales à partir de ces documents qui serviront comme référence pour mettre à jour des bases de connaissances? Concernant la première problématique, nous avons proposé deux méthodes. La première proposition est totalement supervisée. Elle se base sur un modèle de langue de vitalité. La deuxième proposition mesure la fraîcheur des expressions temporelles contenues dans un document afin de décider de sa vitalité. En ce qui concerne la deuxième problématique relative à l'extraction d'informations vitales à partir des documents vitaux, nous avons proposé une méthode qui sélectionne les phrases comportant potentiellement ces informations vitales, en nous basant sur la présence de mots déclencheurs récupérés automatiquement à partir de la connaissance déjà représentée dans la base de connaissances (comme la description d'entités similaires).L'évaluation des approches proposées a été effectuée dans le cadre de la campagne d'évaluation internationale TREC sur une collection de 1.2 milliard de documents avec différents types d'entités (personnes, organisations, établissements et événements). Pour les approches de filtrage de documents vitaux, nous avons mené nos expérimentations dans le cadre de la tâche "Knwoledge Base Acceleration (KBA)" pour les années 2013 et 2014. L'exploitation des expressions temporelles dans le document a permis d'obtenir de bons résultats dépassant le meilleur système proposé dans la tâche KBA 2013. Pour évaluer les contributions concernant l'extraction des informations vitales relatives à des entités, nous nous sommes basés sur le cadre expérimental de la tâche "Temporal Summarization (TS)". Nous avons montré que notre approche permet de minimiser le temps de latence des mises à jour de bases de connaissances
Filtering News from Document Streams: Evaluation Aspects and Modeled Stream Utility
Events like hurricanes, earthquakes,
or accidents can impact a large number of people. Not only are people in the
immediate vicinity of the event affected, but concerns about their well-being are
shared by the local government and well-wishers across the world.
The latest information about news events
could be of use to government and aid agencies in order to make informed decisions on
providing necessary support, security and relief. The general public
avails of news updates via dedicated news feeds or broadcasts, and lately,
via social media services
like Facebook or Twitter.
Retrieving the latest information about newsworthy events from the world-wide web
is thus of importance to a large section of society.
As new content on a multitude of topics is continuously being published on the web,
specific event related information needs to be filtered from the resulting
stream of documents.
We present in this thesis, a user-centric evaluation measure for
evaluating systems that filter news related information from document streams.
Our proposed evaluation measure, Modeled Stream Utility (MSU), models
users accessing information from a stream of sentences
produced by a news update filtering system.
The user model allows for simulating a large number of users with different
characteristic stream browsing behavior. Through simulation,
MSU estimates the utility of a system for an
average user browsing a stream of sentences.
Our results show that system performance is sensitive to a user population's
stream browsing behavior and that
existing evaluation metrics correspond to very specific types of user behavior.
To evaluate systems that filter sentences from a document stream,
we need a set of judged sentences. This judged set is
a subset of all the sentences returned by all systems, and is
typically constructed by pooling
together the highest quality sentences,
as determined by respective system assigned scores for each sentence.
Sentences in the pool are manually assessed and
the resulting set of judged sentences is then used to compute system performance metrics.
In this thesis, we investigate the effect of including duplicates of
judged sentences, into the judged set, on system performance evaluation. We also develop an
alternative pooling methodology, that given the MSU user model,
selects sentences for pooling based on the probability of a sentences being read by
modeled users.
Our research lays the foundation for interesting future work for utilizing
user-models in different aspects of evaluation of stream filtering systems.
The MSU measure enables incorporation of different
user models. Furthermore, the applicability of MSU could be extended through
calibration based on user
behavior
Recommended from our members
A user-centred approach to information retrieval
A user model is a fundamental component in user-centred information retrieval systems. It enables personalization of a user's search experience. The development of such a model involves three phases: collecting information about each user, representing such information, and integrating the model into a retrieval application. Progress in this area is typically met with privacy and scalability challenges that hinder the ability to synthesize collective knowledge from each user's search behaviour. In this thesis, I propose a framework that addresses each of these three phases. The proposed framework is based on social role theory from the social science literature and at the centre of this theory is the concept of a social position. A social position is a label for a group of users with similar behavioural patterns. Examples of such positions are traveller, patient, movie fan, and computer scientist. In this thesis, a social position acts as a label for users who are expected to have similar interests. The proposed framework does not require real users' data; rather it uses the web as a resource to model users.
The proposed framework offers a data-driven and modular design for each of the three phases of building a user model. First, I present an approach to identify social positions from natural language sentences. I formulate this task as a binary classification task and develop a method to enumerate candidate social positions. The proposed classifier achieves an accuracy score of 85.8%, which indicates that social positions can be identified with good accuracy. Through an inter-annotator agreement study, I further show a reasonable level of agreement between users when identifying social positions.
Second, I introduce a novel topic modelling-based approach to represent each social position as a multinomial distribution over words. This approach estimates a topic from a document collection for each position. To construct such a collection for a particular position, I propose a seeding algorithm that extracts a set of terms relevant to the social position. Coherence-based evaluation shows that the proposed approach learns significantly more coherent representations when compared with a relevance modelling baseline.
Third, I present a diversification approach based on the proposed framework. Diversification algorithms aim to return a result list for a search query that would potentially satisfy users with diverse information needs. I propose to identify social positions that are relevant to a search query. These positions act as an implicit representation of the many possible interpretations of the search query. Then, relevant positions are provided to a diversification technique that proportionally diversifies results based on each social position's importance. I evaluate my approach using four test collections provided by the diversity task of the Text REtrieval Conference (TREC) web tracks for 2009, 2010, 2011, and 2012. Results demonstrate that my proposed diversification approach is effective and provides statistically significant improvements over various implicit diversification approaches.
Fourth, I introduce a session-based search system under the framework of learning to rank. Such a system aims to improve the retrieval performance for a search query using previous user interactions during the search session. I present a method to match a search session to its most relevant social positions based on the session's interaction data. I then suggest identifying related sessions from query logs that are likely to be issued by users with similar information needs. Novel learning features are then estimated from the session's social positions, related sessions, and interaction data. I evaluate the proposed system using four test collections from the TREC session track. This approach achieves state-of-the-art results compared with effective session-based search systems. I demonstrate that such a strong performance is mainly attributed to features that are derived from social positions' data
Recommended from our members
History Modeling for Conversational Information Retrieval
Conversational search is an embodiment of an iterative and interactive approach to information retrieval (IR) that has been studied for decades. Due to the recent rise of intelligent personal assistants, such as Siri, Alexa, AliMe, Cortana, and Google Assistant, a growing part of the population is moving their information-seeking activities to voice- or text-based conversational interfaces. One of the major challenges of conversational search is to leverage the conversation history to understand and fulfill the users\u27 information needs. In this dissertation work, we investigate history modeling approaches for conversational information retrieval. We start from history modeling for user intent prediction. We analyze information-seeking conversations by user intent distribution, co-occurrence, and flow patterns, followed by a study of user intent prediction in an information-seeking setting with both feature-based methods and deep learning methods. We then move to history modeling for conversational question answering (ConvQA), which can be considered as a simplified setting of conversational search. We first propose a positional history answer embedding (PosHAE) method to seamlessly integrate conversation history into a ConvQA model based on BERT. We then build upon this method and design a history attention mechanism (HAM) to conduct a ``soft selection\u27\u27 for conversation history. After this, we extend the previous ConvQA task to an open-retrieval (ORConvQA) setting to emphasize the fundamental role of retrieval in conversational search. In this setting, we learn to retrieve evidence from a large collection before extracting answers. We build an end-to-end system for ORConvQA, featuring a learnable dense retriever. We conduct experiments with both fully-supervised and weakly-supervised approaches to tackle the training challenges of ORConvQA. Finally, we study history modeling for conversational re-ranking. Given a history of user feedback behaviors, such as issuing a query, clicking a document, and skipping a document, we propose to introduce behavior awareness to a neural ranker. Our experimental results show that the history modeling approaches proposed in this dissertation can effectively improve the performance of different conversation tasks and provide new insights into conversational information retrieval
Supervised extractive summarisation of news events
This thesis investigates whether the summarisation of news-worthy events can be improved by using evidence about entities (i.e.\ people, places, and organisations) involved in the events. More effective event summaries, that better assist people with their news-based information access requirements, can help to reduce information overload in today's 24-hour news culture.
Summaries are based on sentences extracted verbatim from news articles about the events. Within a supervised machine learning framework, we propose a series of entity-focused event summarisation features. Computed over multiple news articles discussing a given event, such entity-focused evidence estimates: the importance of entities within events; the significance of interactions between entities within events; and the topical relevance of entities to events.
The statement of this research work is that augmenting supervised summarisation models, which are trained on discriminative multi-document newswire summarisation features, with evidence about the named entities involved in the events, by integrating entity-focused event summarisation features, we will obtain more effective summaries of news-worthy events.
The proposed entity-focused event summarisation features are thoroughly evaluated over two multi-document newswire summarisation scenarios. The first scenario is used to evaluate the retrospective event summarisation task, where the goal is to summarise an event to-date, based on a static set of news articles discussing the event. The second scenario is used to evaluate the temporal event summarisation task, where the goal is to summarise the changes in an ongoing event, based on a time-stamped stream of news articles discussing the event.
The contributions of this thesis are two-fold. First, this thesis investigates the utility of entity-focused event evidence for identifying important and salient event summary sentences, and as a means to perform anti-redundancy filtering to control the volume of content emitted as a summary of an evolving event. Second, this thesis also investigates the validity of automatic summarisation evaluation metrics, the effectiveness of standard summarisation baselines, and the effective training of supervised machine learned summarisation models