The Odyssey Approach for Optimizing Federated SPARQL Queries

Answering queries over a federation of SPARQL endpoints requires combining data from more than one data source. Optimizing queries in such scenarios is particularly challenging not only because of (i) the large variety of possible query execution plans that correctly answer the query but also because (ii) there is only limited access to statistics about schema and instance data of remote sources. To overcome these challenges, most federated query engines rely on heuristics to reduce the space of possible query execution plans or on dynamic programming strategies to produce optimal plans. Nevertheless, these plans may still exhibit a high number of intermediate results or high execution times because of heuristics and inaccurate cost estimations. In this paper, we present Odyssey, an approach that uses statistics that allow for a more accurate cost estimation for federated queries and therefore enables Odyssey to produce better query execution plans. Our experimental results show that Odyssey produces query execution plans that are better in terms of data transfer and execution time than state-of-the-art optimizers. Our experiments using the FedBench benchmark show execution time gains of at least 25 times on average.Comment: 16 pages, 10 figure

Situated Support for Choice of Representations

As more and more companies are augmenting their data to include semantics it is imperative that the choices made when choosing the modelling language are well founded in knowledge about the language and the domain in question. This work demonstrates how the Semiotic Quality Framework can facilitate the choice of the most suited language for a real world application. Computational and situated features are introduced as an extension to the framework

Strategies for executing federated queries in SPARQL1.1

A common way for exposing RDF data on the Web is by means of SPARQL endpoints which allow end users and applications to query just the RDF data they want. However, servers hosting SPARQL endpoints often restrict access to the data by limiting the amount of results returned per query or the amount of queries per time that a client may issue. As this may affect query completeness when using SPARQL1.1's federated query extension, we analysed different strategies to implement federated queries with the goal to circumvent endpoint limits. We show that some seemingly intuitive methods for decomposing federated queries provide unsound results in the general case, and provide fixes or discuss under which restrictions these recipes are still applicable. Finally, we evaluate the proposed strategies for checking their feasibility in practice

Co-evolution of RDF Datasets

Linking Data initiatives have fostered the publication of large number of RDF datasets in the Linked Open Data (LOD) cloud, as well as the development of query processing infrastructures to access these data in a federated fashion. However, different experimental studies have shown that availability of LOD datasets cannot be always ensured, being RDF data replication required for envisioning reliable federated query frameworks. Albeit enhancing data availability, RDF data replication requires synchronization and conflict resolution when replicas and source datasets are allowed to change data over time, i.e., co-evolution management needs to be provided to ensure consistency. In this paper, we tackle the problem of RDF data co-evolution and devise an approach for conflict resolution during co-evolution of RDF datasets. Our proposed approach is property-oriented and allows for exploiting semantics about RDF properties during co-evolution management. The quality of our approach is empirically evaluated in different scenarios on the DBpedia-live dataset. Experimental results suggest that proposed proposed techniques have a positive impact on the quality of data in source datasets and replicas.Comment: 18 pages, 4 figures, Accepted in ICWE, 201

Square-planar alkylidyne–osmium and five-coordinate alkylidene–osmium complexes: controlling the transformation from hydride-alkylidyne to alkylidene

This is an open access article published under an ACS AuthorChoice License.Square-planar alkylidyne and five-coordinate alkylidene mixed iPr3P–Os–IPr (IPr = 1,3-bis(diisopropylphenyl)imidazolylidene) complexes have been discovered and characterized, and their formation has been rationalized. The cationic five-coordinate hydride-alkylidyne compounds [OsHX(≡CPh)(IPr)(PiPr3)]OTf (X = Cl (1), F (4); OTf = CF3SO3) undergo deprotonation with KOtBu to afford the trans-halide-alkylidyne square-planar derivatives OsX(≡CPh)(IPr)(PiPr3) (X = Cl (2), F (5)). Oxidative addition of the C(sp)–H bond of phenylacetylene and methyl propiolate along the Cl–Os–CPh axis of 2 with the hydrogen atom directed to the alkylidyne leads to alkynyl-cis-hydride-alkylidyne intermediates, which rapidly evolve into the five-coordinate alkylidene complexes Os(C≡CR)Cl(═CHPh)(IPr)(PiPr3) (R = Ph (6), CO2Me (7)) as a consequence of the migration of the hydride from the metal center to the Cα atom of the alkylidyne. Oxidative addition of the C(sp)–H bond of methyl propiolate along the X–Os–CPh axis of 2 and 5 with the hydrogen atom directed to the halide gives the alkynyl-trans-hydride-alkylidyne derivatives OsH(C≡CCO2Me)X(≡CPh)(IPr)(PiPr3) (X = Cl (8), F (9)). Complex 8 evolves into 7. However, complex 9 containing the stronger π-donor fluoride is stable. The oxidative addition of HCl to 2 selectively yields the cis-hydride-alkylidyne compound OsHCl2(≡CPh)(IPr)(PiPr3) (10), which is also stable.Financial support from the Spanish MINECO (Projects CTQ2014-52799-P, Red de Excelencia Consolider CTQ2014-51912-REDC), the DGA (E35), and the European Social Fund (FSE) is acknowledged. J.J.F.C. acknowledges support via a predoctoral fellowship from the DGA.Peer reviewe

Análisis del grado de difusión de los ODS en las memorias de sostenibilidad orientado a la estrategia de comunicación corporativa

[EN] The Sustainable Development Goals (SDGs) are at the heart of the management of public and private enterprises. Organizations have incorporated the SDGs into their business strategy by developing actions that they disseminate in their reports. In the last decade, academic research has paid special attention to this development, publishing a growing number of studies on the subject with the emergence of a specific line of research in the area of sustainability: sustainability reporting. In this context, this paper aims to show a methodology that serves as a tool to analyze the disclosure of SDGs in the sustainability reports. This methodology has three stages. First, a lexicographic analysis of sustainability reports has been carried out, second, a correspondence analysis, and third, outlining through “guided questions” how the information obtained can be useful to analyze SDG communication strategy. For further illustration the methodology has been applied to a company in the Spanish agri-food sector: Ebro Foods. This work has both academic and professional implications by providing a guideline for SDG dissemination analysis in sustainability reports and, on the other hand, by providing the business world with an analysis tool that serves to improve communication strategies in the field of sustainability.[ES] Los Objetivos de Desarrollo Sostenible (ODS) ocupan un lugar central en la gestión de las empresas públicas y privadas. Las organizaciones han incorporado los ODS en su estrategia de negocio desarrollando acciones que difunden en sus memorias. En la última década, la investigación académica ha prestado especial atención a esta realidad publicándose un creciente número de estudios al respecto y apareciendo una línea de investigación específica en el área de la sostenibilidad: sustainability reporting. En este contexto, este trabajo tiene como objetivo presentar una metodología que sirva como herramienta para analizar el grado de difusión de los ODS en las memorias de sostenibilidad. Dicha metodología consta de tres etapas: en primer lugar, un análisis lexicográfico de las memorias de sostenibilidad; en segundo lugar, un análisis de correspondencias y; finalmente, se muestra, en forma de preguntas-guía cómo la información obtenida puede ser de ayuda para la estrategia de comunicación de los ODS. Para ilustrar esta metodología, se ha aplicado en los informes de sostenibilidad del período 2016-2021 en una empresa del sector agroalimentario: Ebro Foods. Este trabajo tiene implicaciones tanto de tipo teórico como práctico, al aportar una pauta de análisis de la difusión de los ODS en las memorias de sostenibilidad y, por otra parte, al facilitar al mundo empresarial una herramienta de análisis que sirva para mejorar las estrategias de comunicación en el ámbito de la sostenibilidad

Preliminary Results from the Experimental Study of CO2-Brine-Rock Interactions at Elevated T & P: Implications for the Pilot Plant for CO2 Storage in Spain

AbstractA new experimental program has been carried out in order to study CO2-brine-rock interactions susceptible to take place in conditions close to those expected in the pilot plant that is being developed in Spain (a carbonate reservoir located at more than 800 m depth, with 15% porosity, and a salinity of the native brine between 20 – 90g/L). The combination of preliminary experimental and numerical modeling (PHREEQC) results suggests that the main geochemical processes are calcite dissolution and anhydrite precipitation