Bridging the gap between the semantic web and big data: answering SPARQL queries over NoSQL databases

Nowadays, the database field has gotten much more diverse, and as a result, a variety of non-relational (NoSQL) databases have been created, including JSON-document databases and key-value stores, as well as extensible markup language (XML) and graph databases. Due to the emergence of a new generation of data services, some of the problems associated with big data have been resolved. In addition, in the haste to address the challenges of big data, NoSQL abandoned several core databases features that make them extremely efficient and functional, for instance the global view, which enables users to access data regardless of how it is logically structured or physically stored in its sources. In this article, we propose a method that allows us to query non-relational databases based on the ontology-based access data (OBDA) framework by delegating SPARQL protocol and resource description framework (RDF) query language (SPARQL) queries from ontology to the NoSQL database. We applied the method on a popular database called Couchbase and we discussed the result obtained

Recent Trends in Monitoring of European Water Framework Directive Priority Substances Using Micro-Sensors: A 2007–2009 Review

This review discusses from a critical perspective the development of new sensors for the measurement of priority pollutants targeted in the E.U. Water Framework Directive. Significant advances are reported in the paper and their advantages and limitations are also discussed. Future perspectives in this area are also pointed out in the conclusions. This review covers publications appeared since December 2006 (the publication date of the Swift report). Among priority substances, sensors for monitoring the four WFD metals represent 81% of published papers. None of analyzed publications present a micro-sensor totally validated in laboratory, ready for tests under real conditions in the field. The researches are mainly focused on the sensing part of the micro-sensors. Nevertheless, the main factor limiting micro-sensor applications in the environment is the ruggedness of the receptor towards environmental conditions. This point constitutes the first technological obstacle to be overcome for any long-term field tests

Structural study and electrochemical behavior of KPb4‐xCdx(PO4)3 (0≤x≤2) in capturing mercury (II) at graphite electrode

A novel mercury (II) sensor was developed by modifying carbon paste electrode by anion‐deficient apatite. The later was synthesized using solid reaction and characterized with XRD, FTIR, Raman and electrochemical techniques. The refinement results with Rietveld method shows good agreement between the experimental and calculated XRD patterns with satisfactory reliability factors. All experimental variables involved in the differential pulse anodic stripping voltammetric (DPASV) method were optimized to develop a reliable method to measure low concentration of mercury (II). The interference experiments show that Ag (I), Pb (II), Cd (II), Fe (II) and Cu (II) had little or no influence on the Hg (II) signal. Moreover, the prepared electrode revealed good repeatability. The practicability of proposed method for the determination of Hg (II) in fish and seawater samples has shown the satisfactory results