More than 2 millions of new books are published every year and choosing a good book among the huge amount of available options can be a challenging endeavor. Recommender systems help in choosing books by providing personalized suggestions based on the user reading history. However, most book recommender systems are based on collaborative filtering, involving a long onboarding process that requires to rate many books before providing good recommendations. Tinderbook provides book recommendations, given a single book that the user likes, through a card-based playful user interface that does not require an account creation. Tinderbook is strongly rooted in semantic technologies, using the DBpedia knowledge graph to enrich book descriptions and extending a hybrid state-of-the-art knowledge graph embeddings algorithm to derive an item relatedness measure for cold start recommendations. Tinderbook is publicly available ( http://www.tinderbook.it ) and has already generated interest in the public, involving passionate readers, students, librarians, and researchers. The online evaluation shows that Tinderbook achieves almost 50% of precision of the recommendations.

Knowledge Graphs have proven to be extremely valuable to recommender systems, as they enable hybrid graph-based recommendation models encompassing both collaborative and content information. Leveraging this wealth of heterogeneous information for top-N item recommendation is a challenging task, as it requires the ability of effectively encoding a diversity of semantic relations and connectivity patterns. In this work, we propose entity2rec, a novel approach to learning user-item relatedness from knowledge graphs for top-N item recommendation. We start from a knowledge graph modeling user-item and item-item relations and we learn property-specific vector representations of users and items applying neural language models on the network. These representations are used to create property-specific user-item relatedness features, which are in turn fed into learning to rank algorithms to learn a global relatedness model that optimizes top-N item recommendations. We evaluate the proposed approach in terms of ranking quality on the MovieLens 1M dataset, outperforming a number of state-of-the-art recommender systems, and we assess the importance of property-specific relatedness scores on the overall ranking quality.

In this paper, we present the 3cixty Knowledge Base, which collects and harmonizes descriptions of events, places, transportation facilities and user-generated data such as reviews of the city and Expo site of Milan. This knowledge base is used by a set of web and mobile applications to guide Expo Milano 2015 visitors in the city and in the exhibit, allowing them to find places, satellite events and transportation facilities around Milan. As of July 24th, 2015 the knowledge base contains 18665 unique events, 225821 unique places, 94789 reviews, and 9343 transportation facilities, collected from several static, near- and real time local and global data providers, including Expo Milano 2015 official services and numerous social media platforms. The ontologies used as a backbone for structuring the knowledge base follow a rigorous development method where the design principle has generally been to re-use existing ontologies when they exist. We think that the lessons learned from this development will be useful for similar endeavors in other cities or large events around the world with a similar ecosystem of data provisioning services.

The Web enables to have access to silo-ed information describing news articles, often offering a multitude of viewpoints that, once combined, can provide a broader picture of the story being reported on the news. In this paper, we propose an approach that automatically extracts representative features of a news item, namely named entities, from textual content attached to a video item (subtitles) and from a set of documents from the Web collected using entity expansion techniques. Approaches relying on entity expansion generally try to collect and process the important facts behinds a particular news item, but they are often too dependent on frequency-based functions and information retrieval techniques thus neglecting the multi-dimensional relationships that are established among the entities. We propose a concentric-based approach that enables to represent the context of a news item, by harmonizing into a single model the representative entities, which can be extracted using information retrieval and natural language processing techniques (Core), and other entities that get prominent according to different dimensions such as informativeness, semantic connectivity, or popularity (Crust). We compare our approach with a baseline by analyzing the compactness of the generated summary on an existing gold standard available on the Web. Results of the experiments show that our approach converges faster to the ideal compact news snapshot with an improvement of 36.9% over the baseline.

We live in a constantly evolving world where news stories and relevant facts are happening every moment. For each of those stories, numerous news articles, posts, and social media reactions are created, offering a multitude of viewpoints about what is happening around us. Many applications have tried to deal with this complexity from very different angles, targeting particular needs, reconstructing certain parts of the story, and exploiting certain visualization paradigms. In this paper, we identify those challenges and study how an adequate news story representation can effectively support the different phases of the news consumption process. We propose an innovative model called News Semantic Snapshot (NSS) that is designed to capture the entire context of a news item. This model can feed very different applications assisting the users before, during, and after the news story consumption. It formalizes a duality in the news annotations that distinguishes between representative entities and relevant entities, and considers different relevancy dimensions that are incorporated into the model in the form of concentric layers. Finally, we analyze the impact of this NSS on existing prototypes and how it can support future ones.

We present GERBIL, an evaluation framework for semantic entity annotation. The rationale behind our framework is to provide developers, end users and researchers with easy-to-use interfaces that allow for the agile, fine-grained and uniform evaluation of annotation tools on multiple datasets. By these means, we aim to ensure that both tool developers and end users can derive meaningful insights pertaining to the extension, integration and use of annotation applications. In particular, GERBIL provides comparable results to tool developers so as to allow them to easily discover the strengths and weaknesses of their implementations with respect to the state of the art. With the permanent experiment URIs provided by our framework, we ensure the reproducibility and archiving of evaluation results. Moreover, the framework generates data in machine-processable format, allowing for the efficient querying and post-processing of evaluation results. Finally, the tool diagnostics provided by GERBIL allows deriving insights pertaining to the areas in which tools should be further refined, thus allowing developers to create an informed agenda for extensions and end users to detect the right tools for their purposes. GERBIL aims to become a focal point for the state of the art, driving the research agenda of the community by presenting comparable objective evaluation results.