Examinando por Materia "SPARQL"
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- Artículo de Publicación PeriódicaMapping spatiotemporal data to RDF: a SPARQL endpoint for Brussels(2019) Vaisman, Alejandro Ariel; Chentout, Kevin"This paper describes how a platform for publishing and querying linked open data for the Brussels Capital region in Belgium is built. Data are provided as relational tables or XML documents and are mapped into the RDF data model using R2RML, a standard language that allows defining customized mappings from relational databases to RDF datasets. In this work, data are spatiotemporal in nature; therefore, R2RML must be adapted to allow producing spatiotemporal Linked Open Data.Data generated in this way are used to populate a SPARQL endpoint, where queries are submitted and the result can be displayed on a map. This endpoint is implemented using Strabon, a spatiotemporal RDF triple store built by extending the RDF store Sesame. The first part of the paper describes how R2RML is adapted to allow producing spatial RDF data and to support XML data sources. These techniques are then used to map data about cultural events and public transport in Brussels into RDF. Spatial data are stored in the form of stRDF triples, the format required by Strabon. In addition, the endpoint is enriched with external data obtained from the Linked Open Data Cloud, from sites like DBpedia, Geonames, and LinkedGeoData, to provide context for analysis. The second part of the paper shows, through a comprehensive set of the spatial extension to SPARQL (stSPARQL) queries, how the endpoint can be exploited."
- Ponencia en CongresoQuerying semantic web data cubes(2016) Etcheverry, Lorena; Vaisman, Alejandro Ariel"We address the problem of querying data cubes for Online Analytical Processing (OLAP) analysis, directly on the Semantic Web (SW). We rst introduce CQL, a simple algebra for querying data cubes at a conceptual level. Taking advantage of QB4OLAP metadata, we automatically translate CQL queries into SPARQL ones, and propose query optimization strategies that adapt, to the particular OLAP set ting, general-purpose techniques. A web application allows exploring and querying OLAP cubes on the SW, using the machinery presented here."
- Ponencia en CongresoAn RDF vocabulary for meta-programming with SPARQL algebra(2016) Ceriani, Miguel; Vaisman, Alejandro Ariel"SPARQL queries can be represented in RDF in order to work with them as first-class citizen in Semantic Web applications. The representation used so far, SPIN SPARQL, closely follows the abstract syntax tree, but fails to di rectly capture the semantics and is hard to work with for query rewriting. Here a novel vocabulary based on SPARQL Algebra is presented. The adequacy of the language is empirically shown through a few examples. "