MuG: A Multilevel Graph Representation for Big Data Interpretation

Our society is oriented towards data production. The increasingly massive spread of mobile devices and the Internet of Things is transforming our society into a data factory. Data, however, does not immediately lead to knowledge and, in fact we can become overwhelmed with a mass of information that is difficult to understand: often the desire to predict the future from data analysis turns into the nightmare of data overload. There are numerous approaches, automatic and manual, present in the literature that try to interpret data by extracting information. Among the various methodologies proposed, none seems to have resolved the problem in a definitive and universal way, perhaps because every data analysis problem needs to be faced from a different point of view. This paper introduces an approach for the interpretation of data from sensors located within a city. Three graphs (Ontologies, Context Dimension Tree and Bayesian Networks) were chosen for the representation of the scenarios both from the point of view of the sensors involved and of the services and events connected to the data. Through the Ontologies and the Context Dimension Tree it is possible to analyze the scenario from a syntactic and semantic point of view constructing Bayes networks that enable the estimation of the probability that some events happen. A first empirical analysis conducted on some districts of London seems to confirm the effectiveness of the proposed method

Tighter Bounds on Directed Ramsey Number R(7)

Tournaments are orientations of the complete graph, and the directed Ramsey number $R(k)$ is the minimum number of vertices a tournament must have to be guaranteed to contain a transitive subtournament of size $k$, which we denote by $TT_k$. We include a computer-assisted proof of a conjecture by Sanchez-Flores that all $TT_6$-free tournaments on 24 and 25 vertices are subtournaments of $ST_{27}$, the unique largest TT_6-free tournament. We also classify all $TT_6$-free tournaments on 23 vertices. We use these results, combined with assistance from SAT technology, to obtain the following improved bounds: $34 \leq R(7) \leq 47$

A Survey of the First 20 Years of Research on Semantic Web and Linked Data

International audienceThis paper is a survey of the research topics in the field of Semantic Web, Linked Data and Web of Data. This study looks at the contributions of this research community over its first twenty years of existence. Compiling several bibliographical sources and bibliometric indicators , we identify the main research trends and we reference some of their major publications to provide an overview of that initial period. We conclude with some perspectives for the future research challenges.Cet article est une étude des sujets de recherche dans le domaine du Web sémantique, des données liées et du Web des données. Cette étude se penche sur les contributions de cette communauté de recherche au cours de ses vingt premières années d'existence. En compilant plusieurs sources bibliographiques et indicateurs bibliométriques, nous identifions les principales tendances de la recherche et nous référençons certaines de leurs publications majeures pour donner un aperçu de cette période initiale. Nous concluons avec une discussion sur les tendances et perspectives de recherche

On Formal Methods for Large-Scale Product Configuration

<p>In product development companies mass customization is widely used to achieve better customer satisfaction while keeping costs down. To efficiently implement mass customization, product platforms are often used. A product platform allows building a wide range of products from a set of predefined components. The process of matching these components to customers' needs is called product configuration. Not all components can be combined with each other due to restrictions of various kinds, for example, geometrical, marketing and legal reasons. Product design engineers develop configuration constraints to describe such restrictions. The number of constraints and the complexity of the relations between them are immense for complex product like a vehicle. Thus, it is both error-prone and time consuming to analyze, author and verify the constraints manually. Software tools based on formal methods can help engineers to avoid making errors when working with configuration constraints, thus design a correct product faster.</p> <p>This thesis introduces a number of formal methods to help engineers maintain, verify and analyze product configuration constraints. These methods provide automatic verification of constraints and computational support for analyzing and refactoring constraints. The methods also allow verifying the correctness of one specific type of constraints, item usage rules, for sets of mutually-exclusive required items, and automatic verification of equivalence of different formulations of the constraints. The thesis also introduces three methods for efficient enumeration of valid partial configurations, with benchmarking of the methods on an industrial dataset.</p> <p>Handling large-scale industrial product configuration problems demands high efficiency from the software methods. This thesis investigates a number of search-based and knowledge-compilation-based methods for working with large product configuration instances, including Boolean satisfiability solvers, binary decision diagrams and decomposable negation normal form. This thesis also proposes a novel method based on supervisory control theory for efficient reasoning about product configuration data. The methods were implemented in a tool, to investigate the applicability of the methods for handling large product configuration problems. It was found that search-based Boolean satisfiability solvers with incremental capabilities are well suited for industrial configuration problems.</p> <p>The methods proposed in this thesis exhibit good performance on practical configuration problems, and have a potential to be implemented in industry to support product design engineers in creating and maintaining configuration constraints, and speed up the development of product platforms and new products.</p

Complex Event Recognition: a comparison between FlinkCEP and the Run-Time Event Calculus

Ο κλάδος της Αναγνώρισης Σύνθετων Γεγονότων πάνω σε ροές από δεδομένα έχει επιδείξει αξιοσημείωτη ανάπτυξη τα τελευταία χρόνια. Τα συστήματα αναγνώρισης σύνθετων γεγονότων περιεργάζονται ροές από δεδομένα με σκοπό τον εντοπισμό σύνθετων φαινομένων, που εκφράζουν σχέσεις ανάμεσα στα δεδομένα εισόδου. Ο αριθμός των συστημάτων που έχουν αναπτυχθεί τα τελευταία χρόνια έχει δημιουργήσει την ανάγκη για μελέτη και σύγκριση των δυνατοτήτων τους. Σε αυτήν την μελέτη επιλέγουμε δύο συστήματα από τις πιο επικρατούσες κατηγορίες. Διαλέγουμε το FlinkCEP από τα συστήματα βασισμένα σε αυτόματα και το RTEC από τα συστήματα που χρησιμοποιούν λογική. Παρουσιάζουμε μια θεωρητική σύγκριση της εκφραστικότητας των δύο συστημάτων, μαζί με μια πειραματική αξιολόγηση της αποδοτικότητας τους, χρησιμοποιώντας πραγματικά δεδομένα.The field of Complex Event Recognition (CER) on streams of data has shown remarkable growth the last few years. CER systems use streaming data in order to detect composite phenomena expressing relations between the input data. The amount of developed CER systems has created the need to examine and compare their capabilities. In this study we have chosen two systems, originating form the most dominant categories. From automata-based approaches we have selected FlinkCEP and from Logic-based systems we have selected RTEC. We present a theoretical comparison of the two systems’ expressiveness, along with an empirical evaluation of the efficiency, using real data