Combining privileged information to improve context-aware recommender systems

A recommender system is an information filtering technology which can be used to predict preference ratings of items (products, services, movies, etc) and/or to output a ranking of items that are likely to be of interest to the user. Context-aware recommender systems (CARS) learn and predict the tastes and preferences of users by incorporating available contextual information in the recommendation process. One of the major challenges in context-aware recommender systems research is the lack of automatic methods to obtain contextual information for these systems. Considering this scenario, in this paper, we propose to use contextual information from topic hierarchies of the items (web pages) to improve the performance of context-aware recommender systems. The topic hierarchies are constructed by an extension of the LUPI-based Incremental Hierarchical Clustering method that considers three types of information: traditional bag-of-words (technical information), and the combination of named entities (privileged information I) with domain terms (privileged information II). We evaluated the contextual information in four context-aware recommender systems. Different weights were assigned to each type of information. The empirical results demonstrated that topic hierarchies with the combination of the two kinds of privileged information can provide better recommendations.FAPESP (grant #2010/20564-8, #2012/13830-9, and #2013/16039-3, São Paulo Research Foundation (FAPESP))CAPE

Named entities as privileged information for hierarchical text clustering

Text clustering is a text mining task which is often used to aid the organization, knowledge extraction, and exploratory search of text collections. Nowadays, the automatic text clustering becomes essential as the volume and variety of digital text documents increase, either in social networks and the Web or inside organizations. This paper explores the use of named entities as privileged information in a hierarchical clustering process, so as to improve clusters quality and interpretation. We carried out an experimental evaluation on three text collections (one written in Portuguese and two written in English) and the results show that named entities can be applied as privileged information to power clustering solution in dynamic text collection scenarios.FAPESP (grant #2010/20564-8, #2012/13830-9, #2013/14757-6 and #2013/16039-3

Applying multi-view based metadata in personalized ranking for recommender systems

In this paper, we propose a multi-view based metadata extraction technique from unstructured textual content in order to be applied in recommendation algorithms based on latent factors. The solution aims at reducing the problem of intense and time-consuming human effort to identify, collect and label descriptions about the items. Our proposal uses a unsupervised learning method to construct topic hierarchies with named entity recognition as privileged information. We evaluate the technique using different recommendation algorithms, and show that better accuracy is obtained when additional information about items is considered.São Paulo Research Foundation (FAPESP) (Grants 2012/13830-9, 2013/16039-3, 2013/22547-1)CAPE

Contextual information extraction using text mining for recommendation systems context sensitive

Com a grande variedade de produtos e serviços disponíveis na Web, os usuários possuem, em geral, muita liberdade de escolha, o que poderia ser considerado uma vantagem se não fosse pela dificuldade encontrada em escolher o produto ou serviço que mais atenda a suas necessidades dentro do vasto conjunto de opções disponíveis. Sistemas de recomendação são sistemas que têm como objetivo auxiliar esses usuários a identificarem itens de interesse em um conjunto de opções. A maioria das abordagens de sistemas de recomendação foca em recomendar itens mais relevantes para usuários individuais, não levando em consideração o contexto dos usuários. Porém, em muitas aplicações é importante também considerar informações contextuais para fazer as recomendações. Por exemplo, um usuário pode desejar assistir um filme com a sua namorada no sábado à noite ou com os seus amigos durante um dia de semana, e uma locadora de filmes na Web pode recomendar diferentes tipos de filmes para este usuário dependendo do contexto no qual este se encontra. Um grande desafio para o uso de sistemas de recomendação sensíveis ao contexto é a falta de métodos para aquisição automática de informação contextual para estes sistemas. Diante desse cenário, neste trabalho é proposto um método para extrair informações contextuais do conteúdo de páginas Web que consiste em construir hierarquias de tópicos do conteúdo textual das páginas considerando, além da bag-of-words tradicional (informação técnica), também informações mais valiosas dos textos como entidades nomeadas e termos do domínio (informação privilegiada). Os tópicos extraídos das hierarquias das páginas Web são utilizados como informações de contexto em sistemas de recomendação sensíveis ao contexto. Neste trabalho foram realizados experimentos para avaliação do contexto extraído pelo método proposto em que foram considerados dois baselines: um sistema de recomendação que não considera informação de contexto e um método da literatura de extração de contexto implementado e adaptado para este mestrado. Além disso, foram utilizadas duas bases de dados. Os resultados obtidos foram, de forma geral, muito bons apresentando ganhos significativos sobre o baseline sem contexto. Com relação ao baseline que extrai informação contextual, o método proposto se mostrou equivalente ou melhor que o mesmo.With the wide variety of products and services available on the web, it is difficult for users to choose the option that most meets their needs. In order to reduce or even eliminate this difficulty, recommender systems have emerged. A recommender system is used in various fields to recommend items of interest to users. Most recommender approaches focus only on users and items to make the recommendations. However, in many applications it is also important to incorporate contextual information into the recommendation process. For example, a user may want to watch a movie with his girlfriend on Saturday night or with his friends during a weekday, and a video store on the Web can recommend different types of movies for this user depending on his context. Although the use of contextual information by recommendation systems has received great focus in recent years, there is a lack of automatic methods to obtain such information for context-aware recommender systems. For this reason, the acquisition of contextual information is a research area that needs to be better explored. In this scenario, this work proposes a method to extract contextual information of Web page content. This method builds topic hierarchies of the pages textual content considering, besides the traditional bag-of-words, valuable information of texts as named entities and domain terms (privileged information). The topics extracted from the hierarchies are used as contextual information in context-aware recommender systems. By using two databases, experiments were conducted to evaluate the contextual information extracted by the proposed method. Two baselines were considered: a recommendation system that does not use contextual information (IBCF) and a method proposed in literature to extract contextual information (\\methodological\" baseline), adapted for this research. The results are, in general, very good and show significant gains over the baseline without context. Regarding the \"methodological\" baseline, the proposed method is equivalent to or better than this baseline

Extraction of context from reviews for recommender systems using text and opinion mining

Atualmente, com a grande sobrecarga de informações, serviços e produtos disponíveis na Web, os usuários tem encontrado dificuldades em identificar o que de fato é relevante para seus interesses e preferências. Sendo assim, sistemas de recomendação estão sendo desenvolvidos e implantados em um número cada vez maior de sites e aplicações com o objetivo de auxiliar os usuários sugerindo itens que atendam às suas preferências e necessidades. A tendência nessa área é a utilização de informações relevantes com o objetivo de gerar recomendações mais personalizadas e precisas aos usuários. Estudos comprovam que o uso de informação contextual tem viabilizado a obtenção de bons resultados na recomendação. Um dos grandes desafios encontrados na área de sistemas de recomendação sensíveis ao contexto refere-se à carência de métodos automáticos para a extração desse tipo de informação. Por outro lado, com o avanço da Web 2.0 e a crescente popularidade de redes sociais e comércio eletrônico, usuários têm sido cada vez mais encorajados a escrever reviews descrevendo suas opiniões sobre os itens. Dessas reviews podem ser extraídas informações importantes a serem utilizadas em sistemas de recomendação como contexto e opiniões. Com isso, o propósito geral deste trabalho de doutorado é avançar as pesquisas da área de sistemas de recomendação sensíveis ao contexto, em especial na extração automática de informações contextuais. Para atender aos objetivos do trabalho, foi realizada uma revisão sistemática da literatura de sistemas de recomendação sensíveis ao contexto que utilizam mineração de opiniões. Levando em consideração a carência de métodos automáticos de extração de contexto assim como a relevância das informações extraídas de reviews de usuários para os sistemas de recomendação, neste trabalho de doutorado foram propostos: (i) um método de recomendação sensível ao contexto, CARM-TOM, que executa desde o pré-processamento das reviews até a geração das recomendações utilizando informações contextuais; (ii) CIET.5embed, uma técnica de extração de contexto baseada em word embeddings; (iii) uma técnica de extração de contexto baseada em regras de associação, a RulesContext; e (iv) uma técnica de extração de contexto baseada em mineração de opiniões no nível dos aspectos, a CEOM. Essas propostas foram avaliadas considerando a base de reviews Yelp, sistemas de recomendação baseados nos vizinhos mais próximos, sistemas de recomendação baseados em fatoração de matrizes e diferentes baselines. Os resultados demonstraram que o uso das informações extraídas pelas técnicas propostas levaram a geração de recomendações mais precisas.Today, with the information, service and product overload on the Web, users have found it difficult to identify what is really relevant to their interests and preferences. Thus, recommender systems are being developed and deployed on an increasing number of websites and applications to assist users in suggesting items that meet their preferences and needs. The trend in this area is the use of relevant information in order to generate more personalized and accurate recommendations to users. Studies show that the use of contextual information has made it possible to obtain good results in the recommendation. One of the major challenges encountered in the context of context-aware recommender systems is the lack of automatic methods for extracting this type of information. On the other hand, with the advancement of Web 2.0 and the growing popularity of social networking and e-commerce, users have been increasingly encouraged to write reviews describing their opinions about the items. From these reviews important information can be extracted for use in recommender systems such as context and opinions. Thus, the general purpose of this doctoral work is to advance research in the area of context-aware recommender systems, especially in the automatic extraction of contextual information. To meet the objectives of the work, a systematic review of context-aware recommender systems using opinion mining has been performed. Taking into account the lack of automatic context extraction methods as well as the relevance of information extracted from user reviews to recommender systems, this doctoral work proposes: (i) a context-aware recommender method, CARM-TOM, which runs from preprocessing reviews to generating recommendations using contextual information; (ii) CIET.5embed, a context extraction technique based on word embeddings; (iii) a context-extraction technique based on association rules, the RulesContext; and (iv) a context extraction technique based on aspect-level opinion mining, the CEOM. These proposals were evaluated using the Yelp review datset, nearest neighbor-based recommender systems, matrix factorization-based recommender systems, and different baselines. The results showed that the use of the information extracted by the proposed techniques led to the generation of more accurate recommendations

Using Opinion Mining in Context-Aware Recommender Systems: A Systematic Review

Recommender systems help users by recommending items, such as products and services, that can be of interest to these users. Context-aware recommender systems have been widely investigated in both academia and industry because they can make recommendations based on a user’s current context (e.g., location and time). Moreover, the advent of Web 2.0 and the growing popularity of social and e-commerce media sites have encouraged users to naturally write texts describing their assessment of items. There are increasing efforts to incorporate the rich information embedded in user’s reviews/texts into the recommender systems. Given the importance of this type of texts and their usage along with opinion mining and contextual information extraction techniques for recommender systems, we present a systematic review on the recommender systems that explore both contextual information and opinion mining. This systematic review followed a well-defined protocol. Its results were based on 17 papers, selected among 195 papers identified in four digital libraries. The results of this review give a general summary of the current research on this subject and point out some areas that may be improved in future primary works

Exploiting Text Mining Techniques for Contextual Recommendations

Unlike traditional recommender systems, which make recommendations only by using the relation between users and items, a context-aware recommender system makes recommendations by incorporating available contextual information into the recommendation process. One problem of context-aware approaches is that it is required techniques to extract such additional information in an automatic manner. In this paper, we propose to use two text mining techniques which are applied to textual data to infer contextual information automatically: named entities recognition and topic hierarchies. We evaluate the proposed technique in four context-aware recommender systems. The empirical results demonstrate that by using named entities and topic hierarchies we can provide better recommendations.São Paulo Research Foundation (FAPESP) (grants 2010/20564-8, 2011/19850-9, 2012/13830-9, 2013/16039-3, 2013/22547-1)CAPESCNP