Personality-based recommendation: human curiosity applied to recommendation systems using implicit information from social networks

Tesis por compendioEn el día a día, las personas suelen confiar en recomendaciones, tradicionalmente aportadas por otras personas (familia, amigos, etc.) para sus decisiones más variadas. En el mundo digital esto no es diferente, dado que los sistemas de recomendación están presentes en todas partes y de modo transparente. El principal objetivo de estos sistemas es el de ayudar en el proceso de toma de decisiones, generando recomendaciones de su interés y basadas en sus gustos. Dichas recomendaciones van desde productos en sitios web de comercio electrónico, como libros o lugares a visitar, además de qué comer o cuánto tiempo uno debe caminar al día para tener una vida sana, con quién salir o a quién seguir en las redes sociales. Esta es un área en ascensión. Por un lado, tenemos cada vez más usuarios en internet cuya vida está digitalizada, dado que lo que se hace en el "mundo real" está representado en cierto modo en el "mundo digital". Por otro lado, sufrimos una sobrecarga de información, que puede mitigarse mediante el uso de un sistema de recomendación. Sin embargo, estos sistemas también enfrentan algunos problemas, como el problema del arranque en frío y su necesidad de ser cada vez más "humanos", "personalizados" y "precisos" para satisfacer las exigencias de usuarios y empresas. En este desafiante escenario, los sistemas de recomendación basados en la personalidad se están estudiando cada vez más, ya que son capaces de enfrentar esos problemas. Algunos proyectos recientes proponen el uso de la personalidad humana en los recomendadores, ya sea en su conjunto o individualmente por rasgos. Esta tesis está dedicada a este nuevo área de recomendación basada en la personalidad, centrándose en uno de sus rasgos más importantes, la curiosidad. Además, para explotar la información ya existente en internet, obtendremos de forma implícita información de las redes sociales. Por lo tanto, este trabajo tiene como objetivo proporcionar una mejor experiencia al usuario final a través de un nuevo enfoque que ofrece una alternativa a algunos de los retos identificados en los sistemas de recomendación basados en la personalidad. Entre estas mejoras, el uso de las redes sociales para alimentar los sistemas de recomendación reduce el problema del arranque en frío y, al mismo tiempo, proporciona datos valiosos para la predicción de la personalidad humana. Por otro lado, la curiosidad no ha sido utilizada por ninguno de los sistemas de recomendación estudiados; casi todos han usado la personalidad general de un individuo a través de los Cinco Grandes rasgos de la personalidad. Sin embargo, los estudios psicológicos confirman que la curiosidad es un rasgo relevante en el proceso de elegir un item, cuestión directamente relacionada con los sistemas de recomendación. En resumen, creemos que un sistema de recomendación que mida implícitamente la curiosidad y la utilice en el proceso de recomendar nuevos ítems, especialmente en el sector turístico, podría claramente mejorar la capacidad de estos sistemas en términos de precisión, serendipidad y novedad, permitiendo a los usuarios obtener niveles positivos de satisfacción con las recomendaciones. Esta tesis realiza un estudio exhaustivo del estado del arte, donde destacamos trabajos sobre sistemas de recomendación, la personalidad humana desde el punto de vista de la psicología tradicional y positiva y finalmente cómo se combinan ambos aspectos. Luego, desarrollamos una aplicación en línea capaz de extraer implícitamente información del perfil de usuario en una red social, generando predicciones de uno o más rasgos de su personalidad. Finalmente, desarrollamos el sistema CURUMIM, capaz de generar recomendaciones en línea con diferentes propiedades, combinando la curiosidad y algunas características sociodemográficas (como el nivel de educación) extraídas de Facebook. El sistema ha sido probado y evaluado en el contexto turístico por usuarios rEn el dia a dia, les persones solen confiar en recomanacions, tradicionalment aportades per altres persones (família, amics, etc.) per a les seues decisions més variades. En el món digital això no és diferent, atès que els sistemes de recomanació estan presents a tot arreu i de manera transparent. El principal objectiu d'aquests sistemes és el d'ajudar en el procés de presa de decisions, generant recomanacions del seu interès i basades en els seus gustos. Aquestes recomanacions van des de productes en pàgines web de comerç electrònic, com a llibres o llocs a visitar, a més de què menjar o quant temps una persona ha de caminar al dia per a tindre una vida sana, amb qui eixir o a qui seguir en les xarxes socials. Aquesta és una àrea en ascensió. D'una banda, tenim cada vegada més usuaris en internet la vida de les quals està digitalitzada, atès que el que es fa en el "món real" està representat en certa manera en el "món digital". D'altra banda, patim una sobrecàrrega d'informació, que pot mitigar-se mitjançant l'ús d'un sistema de recomanació. No obstant això, aquests sistemes també enfronten alguns problemes, com el problema de l'arrencada en fred i la seua necessitat de ser cada vegada més "humans", "personalitzats" i "precisos" per a satisfer les exigències d'usuaris i empreses. En aquest desafiador escenari, els sistemes de recomanació basats en la personalitat s'estan estudiant cada vegada més, ja que són capaços d'enfrontar eixos problemes. Alguns projectes recents proposen l'ús de la personalitat humana en els recomendadors, ja siga en el seu conjunt o individualment per trets. Aquesta tesi està dedicada a aquest nou àrea de recomanació basada en la personalitat, centrant-se en un dels seus trets més importants, la curiositat. A més, per a explotar la informació ja existent en internet, obtindrem de forma implícita informació de les xarxes socials. Per tant, aquest treball té com a objectiu proporcionar una millor experiència a l'usuari final a través d'un nou enfocament que ofereix una alternativa a alguns dels reptes identificats en els sistemes de recomanació basats en la personalitat. Entre aquestes millores, l'ús de les xarxes socials per a alimentar els sistemes de recomanació redueix el problema de l'arrencada en fred i, al mateix temps, proporciona dades valuoses per a la predicció de la personalitat humana. D'altra banda, la curiositat no ha sigut utilitzada per cap dels sistemes de recomanació estudiats; quasi tots han usat la personalitat general d'un individu a través dels Cinc Grans trets de la personalitat. No obstant això, els estudis psicològics confirmen que la curiositat és un tret rellevant en el procés de triar un item, qüestió directament relacionada amb els sistemes de recomanació. En resum, creiem que un sistema de recomanació que mesure implícitament la curiositat i la utilitze en el procés de recomanar nous ítems, especialment en el sector turístic, podria clarament millorar la capacitat d'aquests sistemes en termes de precisió, sorpresa i novetat, permetent als usuaris obtindre nivells positius de satisfacció amb les recomanacions. Aquesta tesi realitza un estudi exhaustiu de l'estat de l'art, on destaquem treballs sobre sistemes de recomanació, la personalitat humana des del punt de vista de la psicologia tradicional i positiva i finalment com es combinen tots dos aspectes. Després, desenvolupem una aplicació en línia capaç d'extraure implícitament informació del perfil d'usuari en una xarxa social, generant prediccions d'un o més trets de la seua personalitat. Finalment, desenvolupem el sistema CURUMIM, capaç de generar recomanacions en línia amb diferents propietats, combinant la curiositat i algunes característiques sociodemogràfiques (com el nivell d'educació) extretes de Facebook. El sistema ha sigut provat i avaluat en el context turístic per usuaris reals. Els resultats demostren la seua capacitat perIn daily life, people usually rely on recommendations, traditionally given by other people (family, friends, etc.) for their most varied decisions. In the digital world, this is not different, given that recommender systems are present everywhere in such a way that we no longer realize. The main goal of these systems is to assist users in the decision-making process, generating recommendations that are of their interest and based on their tastes. These recommendations range from products in e-commerce websites, like books to read or places to visit to what to eat or how long one should walk a day to have a healthy life, who to date or who one should follow on social networks. And this is an increasing area. On the one hand, we have more and more users on the internet whose life is somewhat digitized, given than what one does in the "real world" is represented in a certain way in the "digital world". On the other hand, we suffer from information overload, which can be mitigated by the use of recommendation systems. However, these systems also face some problems, such as the cold start problem and their need to be more and more "human", "personalised" and "precise" in order to meet the yearning of users and companies. In this challenging scenario, personality-based recommender systems are being increasingly studied, since they are able to face these problems. Some recent projects have proposed the use of the human personality in recommenders, whether as a whole or individually by facet in order to meet those demands. Therefore, this thesis is devoted to this new area of personality-based recommendation, focusing on one of its most important traits, the curiosity. Additionally, in order to exploit the information already present on the internet, we will implicitly obtain information from social networks. Thus, this work aims to build a better experience for the end user through a new approach that offers an option for some of the gaps identified in personality-based recommendation systems. Among these gap improvements, the use of social networks to feed the recommender systems soften the cold start problem and, at the same time, it provides valuable data for the prediction of the human personality. Another found gap is that the curiosity was not used by any of the studied recommender systems; almost all of them have used the overall personality of an individual through the Big Five personality traits. However, psychological studies confirm that the curiosity is a relevant trait in the process of choosing an item, which is directly related to recommendation systems. In summary, we believe that a recommendation system that implicitly measures the curiosity and uses it in the process of recommending new items, especially in the tourism sector, could clearly improve the capacity of these systems in terms of accuracy, serendipity and novelty, allowing users to obtain positive levels of satisfaction with the recommendations. This thesis begins with an exhaustive study of the state of the art, where we highlight works about recommender systems, the human personality from the point of view of traditional and positive psychology and how these aspects are combined. Then, we develop an online application capable of implicitly extracting information from the user profile in a social network, thus generating predictions of one or more personality traits. Finally, we develop the CURUMIM system, able to generate online recommendations with different properties, combining the curiosity and some sociodemographic characteristics (such as level of education) extracted from Facebook. The system is tested and assessed within the tourism context by real users. The results demonstrate its ability to generate novel and serendipitous recommendations, while maintaining a good level of accuracy, independently of the degree of curiosity of the users.Menk Dos Santos, A. (2018). Personality-based recommendation: human curiosity applied to recommendation systems using implicit information from social networks [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/114798TESISCompendi

Mining Human Mobility Data and Social Media for Smart Ride Sharing

CAPES People living in highly-populated cities increasingly suffer an impoverishment of their quality of life due to pollution and traffic congestion problems caused by the huge number of circulating vehicles. Indeed, the reduction the number of circulating vehicles is one of the most difficult challenges in large metropolitan areas. This PhD thesis proposes a research contribution with the final objective of reducing travelling vehicles. This is done towards two different directions: on the one hand, we aim to improve the efficacy of ride sharing systems, creating a larger number of ride possibilities based on the passengers destination activities; on the other hand, we propose a social media analysis method, based on machine learning, to identify transportation demand to an event. Concerning the first research direction, we investigate a novel approach to boost ride sharing opportunities based, not only on fixed destinations, but also on alternative destinations while preserving the intended activity of the user. We observe that in many cases the activity motivating the use of a private car (e.g., going to a shopping mall) can be performed at many different locations (e.g. all the shopping malls in a given area). Our assumption is that, when there is the possibility of sharing a ride, people may accept visiting an alternative destination to fulfill their needs. Based on this idea, We thus propose Activity-Based Ride Matching (ABRM), an algorithm aimed at matching ride requests with ride offers to alternative destinations where the intended activity can still be performed. By analyzing two large mobility datasets, we found that with our approach there is an increase up to 54.69% in ride-sharing opportunities compared to a traditional fixed-destination-oriented approach. For the second research contribution, we focus on the analysis of social media for inferring the transportation demands for large events such as music festivals and sports games. In this context, we investigate the novel problem of exploiting the content of nongeotagged posts to infer users’ attendance of large events. We identified three temporal periods: before, during and after an event. We detail the features used to train the event attendance classifiers on the three temporal periods and report on experiments conducted on two large music festivals in the UK. Our classifiers attained a very high accuracy, with the highest result observed for Creamfields festival (∼91% accuracy to classify users that will participate in the event). Furthermore, we proposed an example of application of our methodology in event-related transportation. This proposed application aims to evaluate the geographic areas with a higher potential demand for transportation services to an event. Pessoas que vivem em cidades altamente populosas sofrem cada vez mais com o declínio da qualidade de vida devido à poluição e aos problemas de congestionamento causados pelo enorme número de veículos em circulação. A redução da quantidade de veículos em circulação é de fato um dos mais difíceis desafios em grandes áreas metropolitanas. A presente tese de doutorado propõe uma pesquisa com o objetivo final de reduzir o número de veículos em circulação. Tal objetivo é feito em duas diferentes direções: por um lado, pretendemos melhorar a eficácia dos sistemas de ride-sharing aumentando o número de possibilidades de caronas com base na atividade destino dos passageiros; por outro lado, propomos também um método baseado em aprendizagem de máquina e análise de mídia social para identificar demanda de transporte de um evento. Em relação à primeira contribuição da pesquisa, nós investigamos uma nova abordagem para aumentar o compartilhamento de caronas baseando-se não apenas em destinos fixos, mas também em destinos alternativos enquanto que preservando a atividade pretendida do usuário. Observamos que em muitos casos a atividade que motiva o uso de um carro particular (por exemplo ir a um shopping center) pode ser realizada em muitos locais diferentes (por exemplo todos os shoppings em uma determinada área). Nossa suposição é que, quando há a possibilidade de compartilhar uma carona, as pessoas podem aceitar visitas a destinos alternativos para satisfazer suas necessidades. Nós propomos o Activity-Based Ride Matching (ABRM), um algoritmo que visa atender às solicitações de caronas usando destinos alternativos onde a atividade pretendida pelo passageiro ainda pode ser executada. Através da análise de dois grande conjuntos de dados de mobilidade, mostramos que nossa abordagem alcança um aumento de até 54,69% nas oportunidades de caronas em comparação com abordagens tradicionais orientadas a destinos fixos. Para a segunda contribuição nos concentramos na análise de mídias sociais para inferir as demandas de transporte para grandes eventos tais como concertos musicais e eventos esportivos. Investigamos um problema que consiste em explorar o conteúdo de postagens não geolocalizadas para inferir a participação dos usuários em grandes eventos. Nós identificamos três períodos temporais: antes, durante e depois de um evento. Detalhamos as features usadas para treinar classificadores capazes de inferir a participação de usuários em um dado evento nos três períodos temporais. Os experimentos foram conduzidos usando postagens em mídias sociais referentes a dois grandes festivais de música no Reino Unido. Nossos classificadores obtiveram alta accuracy, com o maior resultado observado para o festival Creamfields (∼91% de accuracy para classificar os usuários que participarão do evento). Propusemos também uma aplicação de nosso método que visa avaliar as áreas geográficas com maior potencial de demanda por serviços de transporte para um evento. Le persone che vivono in città densamente popolate subiscono sempre più un impoverimento delle loro qualità della vita a causa dell’inquinamento e dei problemi di congestione del traffico causati dall’enorme numero di veicoli circolanti. La riduzione dei veicoli circolanti è una delle sfide più difficili nelle grandi aree metropolitane. Questa tesi di dottorato propone un contributo di ricerca con l’obiettivo finale di ridurre i numeri di veicoli in viaggio. Questo eśtato sviluppato verso due direzioni: da un lato, vogliamo migliorare l’efficacia dei sistemi di ride sharing, aumentando la possibilità di ricevere e dare passaggi in base alla attività di destinazione dei passeggeri. D’altra parte, vogliamo proporre un metodo basato sul machine learning e analisi dei social media, per identificare demanda de transporte a un evento. Per quanto riguarda il primo contributo di ricerca, abbiamo studiato un nuovo approccio per aumentare la condivisione dei passagi non solo su destinazioni fisse, ma anche su destinazioni alternative preservando l’attività prevista dall’utente. Osserviamo infatti che in molti casi l’attività che motiva l’uso di un’auto privata (ad es. andare in un centro commerciale) può essere eseguito in molti luoghi diversi (ad esempio tutti i centri commerciali in una determinata area). La nostra ipotesi è che, quando c’è la possibilità di condividere un passaggio, le persone possono accettare di visitare una destinazione alternativa per soddisfare i loro bisogni. Basato su questa idea, proponiamo Activity-Based Ride Matching (ABRM), un algoritmo che mira a soddisfare le richieste di carpool utilizzando destinazioni alternative, dove l’attività desiderata dal passeggero può ancora essere eseguita. Attraverso l’analisi di due grandi insiemi di dati di mobilità, mostriamo che il nostro approccio raggiunge un aumento fino al 54,69% nelle opportunità di condivisione di car pooling rispetto agli approcci tradizionali rivolti a destinazioni fisse. Per il secondo contributo della ricerca ci concentriamo sull’analisi dei social media per inferire le richieste di trasporto verso grandi eventi come concerti musicali e giochi sportivi. In questo contesto, indaghiamo sul nuovo problema dello sfruttamento del contenuto di non geotagged post per inferire la presenza di utenti a grandi eventi. Abbiamo identificato tre periodi temporali: prima, durante e dopo un evento. Descriviamo in dettaglio le caratteristiche utilizzate per addestrare i classificatori per inferire la partecipazione all’evento sui tre periodi temporali. Riportiamo gli esperimenti condotti su due grandi festival musicali nel Regno Unito. I nostri classificatori raggiungono uma alta accuracy, con il risultato più alto osservato per il festival Creamfields (∼91% di accuracy per classificare gli utenti che parteciperanno all’evento). Inoltre, abbiamo proposto un’applicazione della nostra metodologia che ha come scopo valutare le aree geografiche con il maggior potenziale di domanda di servizi di trasporto per un evento. Document type: Conference objec

Suchbasierte automatische Bildannotation anhand geokodierter Community-Fotos

In the Web 2.0 era, platforms for sharing and collaboratively annotating images with keywords, called tags, became very popular. Tags are a powerful means for organizing and retrieving photos. However, manual tagging is time consuming. Recently, the sheer amount of user-tagged photos available on the Web encouraged researchers to explore new techniques for automatic image annotation. The idea is to annotate an unlabeled image by propagating the labels of community photos that are visually similar to it. Most recently, an ever increasing amount of community photos is also associated with location information, i.e., geotagged. In this thesis, we aim at exploiting the location context and propose an approach for automatically annotating geotagged photos. Our objective is to address the main limitations of state-of-the-art approaches in terms of the quality of the produced tags and the speed of the complete annotation process. To achieve these goals, we, first, deal with the problem of collecting images with the associated metadata from online repositories. Accordingly, we introduce a strategy for data crawling that takes advantage of location information and the social relationships among the contributors of the photos. To improve the quality of the collected user-tags, we present a method for resolving their ambiguity based on tag relatedness information. In this respect, we propose an approach for representing tags as probability distributions based on the algorithm of Laplacian score feature selection. Furthermore, we propose a new metric for calculating the distance between tag probability distributions by extending Jensen-Shannon Divergence to account for statistical fluctuations. To efficiently identify the visual neighbors, the thesis introduces two extensions to the state-of-the-art image matching algorithm, known as Speeded Up Robust Features (SURF). To speed up the matching, we present a solution for reducing the number of compared SURF descriptors based on classification techniques, while the accuracy of SURF is improved through an efficient method for iterative image matching. Furthermore, we propose a statistical model for ranking the mined annotations according to their relevance to the target image. This is achieved by combining multi-modal information in a statistical framework based on Bayes' rule. Finally, the effectiveness of each of mentioned contributions as well as the complete automatic annotation process are evaluated experimentally.Seit der Einführung von Web 2.0 steigt die Popularität von Plattformen, auf denen Bilder geteilt und durch die Gemeinschaft mit Schlagwörtern, sogenannten Tags, annotiert werden. Mit Tags lassen sich Fotos leichter organisieren und auffinden. Manuelles Taggen ist allerdings sehr zeitintensiv. Animiert von der schieren Menge an im Web zugänglichen, von Usern getaggten Fotos, erforschen Wissenschaftler derzeit neue Techniken der automatischen Bildannotation. Dahinter steht die Idee, ein noch nicht beschriftetes Bild auf der Grundlage visuell ähnlicher, bereits beschrifteter Community-Fotos zu annotieren. Unlängst wurde eine immer größere Menge an Community-Fotos mit geographischen Koordinaten versehen (geottagged). Die Arbeit macht sich diesen geographischen Kontext zunutze und präsentiert einen Ansatz zur automatischen Annotation geogetaggter Fotos. Ziel ist es, die wesentlichen Grenzen der bisher bekannten Ansätze in Hinsicht auf die Qualität der produzierten Tags und die Geschwindigkeit des gesamten Annotationsprozesses aufzuzeigen. Um dieses Ziel zu erreichen, wurden zunächst Bilder mit entsprechenden Metadaten aus den Online-Quellen gesammelt. Darauf basierend, wird eine Strategie zur Datensammlung eingeführt, die sich sowohl der geographischen Informationen als auch der sozialen Verbindungen zwischen denjenigen, die die Fotos zur Verfügung stellen, bedient. Um die Qualität der gesammelten User-Tags zu verbessern, wird eine Methode zur Auflösung ihrer Ambiguität vorgestellt, die auf der Information der Tag-Ähnlichkeiten basiert. In diesem Zusammenhang wird ein Ansatz zur Darstellung von Tags als Wahrscheinlichkeitsverteilungen vorgeschlagen, der auf den Algorithmus der sogenannten Laplacian Score (LS) aufbaut. Des Weiteren wird eine Erweiterung der Jensen-Shannon-Divergence (JSD) vorgestellt, die statistische Fluktuationen berücksichtigt. Zur effizienten Identifikation der visuellen Nachbarn werden in der Arbeit zwei Erweiterungen des Speeded Up Robust Features (SURF)-Algorithmus vorgestellt. Zur Beschleunigung des Abgleichs wird eine Lösung auf der Basis von Klassifikationstechniken präsentiert, die die Anzahl der miteinander verglichenen SURF-Deskriptoren minimiert, während die SURF-Genauigkeit durch eine effiziente Methode des schrittweisen Bildabgleichs verbessert wird. Des Weiteren wird ein statistisches Modell basierend auf der Baye'schen Regel vorgeschlagen, um die erlangten Annotationen entsprechend ihrer Relevanz in Bezug auf das Zielbild zu ranken. Schließlich wird die Effizienz jedes einzelnen, erwähnten Beitrags experimentell evaluiert. Darüber hinaus wird die Performanz des vorgeschlagenen automatischen Annotationsansatzes durch umfassende experimentelle Studien als Ganzes demonstriert

A Collaborative Location Based Travel Recommendation System through Enhanced Rating Prediction for the Group of Users

Rapid growth of web and its applications has created a colossal importance for recommender systems. Being applied in various domains, recommender systems were designed to generate suggestions such as items or services based on user interests. Basically, recommender systems experience many issues which reflects dwindled effectiveness. Integrating powerful data management techniques to recommender systems can address such issues and the recommendations quality can be increased significantly. Recent research on recommender systems reveals an idea of utilizing social network data to enhance traditional recommender system with better prediction and improved accuracy. This paper expresses views on social network data based recommender systems by considering usage of various recommendation algorithms, functionalities of systems, different types of interfaces, filtering techniques, and artificial intelligence techniques. After examining the depths of objectives, methodologies, and data sources of the existing models, the paper helps anyone interested in the development of travel recommendation systems and facilitates future research direction. We have also proposed a location recommendation system based on social pertinent trust walker (SPTW) and compared the results with the existing baseline random walk models. Later, we have enhanced the SPTW model for group of users recommendations. The results obtained from the experiments have been presented

Geospatial Semantics

Geospatial semantics is a broad field that involves a variety of research areas. The term semantics refers to the meaning of things, and is in contrast with the term syntactics. Accordingly, studies on geospatial semantics usually focus on understanding the meaning of geographic entities as well as their counterparts in the cognitive and digital world, such as cognitive geographic concepts and digital gazetteers. Geospatial semantics can also facilitate the design of geographic information systems (GIS) by enhancing the interoperability of distributed systems and developing more intelligent interfaces for user interactions. During the past years, a lot of research has been conducted, approaching geospatial semantics from different perspectives, using a variety of methods, and targeting different problems. Meanwhile, the arrival of big geo data, especially the large amount of unstructured text data on the Web, and the fast development of natural language processing methods enable new research directions in geospatial semantics. This chapter, therefore, provides a systematic review on the existing geospatial semantic research. Six major research areas are identified and discussed, including semantic interoperability, digital gazetteers, geographic information retrieval, geospatial Semantic Web, place semantics, and cognitive geographic concepts.Comment: Yingjie Hu (2017). Geospatial Semantics. In Bo Huang, Thomas J. Cova, and Ming-Hsiang Tsou et al. (Eds): Comprehensive Geographic Information Systems, Elsevier. Oxford, U

Contextual Models for Sequential Recommendation

Recommender systems aim to capture the interests of users in order to provide them with tailored recommendations for items or services they might like. User interests are often unique and depend on many unobservable factors including internal moods or external events. This phenomenon creates a broad range of tasks for recommendation systems that are difficult to address altogether. Nevertheless, analyzing the historical activities of users sheds light on the characteristic traits of individual behaviors in order to enable qualified recommendations. In this thesis, we deal with the problem of comprehending the interests of users, searching for pertinent items, and ranking them to recommend the most relevant items to the users given different contexts and situations. We focus on recommendation problems in sequential scenarios, where a series of past events influences the future decisions of users. These events are either the developed preferences of users over a long span of time or highly influenced by the zeitgeist and common trends. We are among the first to model recommendation systems in a sequential fashion via exploiting the short-term interests of users in session-based scenarios. We leverage reinforcement learning techniques to capture underlying short- and long-term user interests in the absence of explicit feedback and develop novel contextual approaches for sequential recommendation systems. These approaches are designed to efficiently learn models for different types of recommendation tasks and are extended to continuous and multi-agent settings. All the proposed methods are empirically studied on large-scale real-world scenarios ranging from e-commerce to sport and demonstrate excellent performance in comparison to baseline approaches