SPARQL is the standard language for querying on RDF data, however it lacks support for many useful functions that a semantic city service may require. In this paper, a system is discussed where functions written in commonly known programming language like Java can be instantly added to the SPARQL function library, thereby decreasing development time as well as keeping the underlying implementat...

With this poster, we will present the Linked SPARQL Query (LSQ) dataset, which describes SPARQL queries taken from the logs of public endpoints. We introduce the initial four query logs that we have taken and the extraction process applied: the types of meta-data captured, how the data are modelled, what vocabularies we use, etc. The LSQ dataset currently contains 73 million triples describing ...

According to the predictive results of query performance, queries can be rewritten to reduce time cost or rescheduled to the time when the resource is not in contention. As more large RDF datasets appear on the Web recently, predicting performance of SPARQL query processing is one major challenge in managing a large RDF dataset efficiently. In this paper, we focus on representing SPARQL queries...

SPARQL query language is targeted to search datasets encoded in RDF. SPARQL Update adds support of insert and delete operations between graph stores, enabling queries to process data in steps, have persistent memory and communicate with each other. When used in a system supporting incremental evaluation of multiple simultaneously active and collaborating queries SPARQL can define entire event p...

We extend the Semantic Web query language SPARQL by defining the semantics of SPARQL queries under the entailment regimes of RDF, RDFS, and OWL. The proposed extensions are part of the SPARQL 1.1 Entailment Regimes working draft which is currently being developed as part of the W3C standardization process of SPARQL 1.1. We review the conditions that SPARQL imposes on such extensions, discuss th...

The SPARQL Query Language for RDF and the SPARQL Protocol for RDF are implemented by a growing number of storage systems and are used within enterprise and open Web settings. As SPARQL is taken up by the community, there is a growing need for benchmarks to compare the performance of storage systems that expose SPARQL endpoints via the SPARQL protocol. Such systems include native RDF stores as w...

SPARQL is the standard query language for RDF graphs. In its strict instantiation, it only offers querying according to the RDF semantics and would thus ignore the semantics of data expressed with respect to (RDF) schemas or (OWL) ontologies. Several extensions to SPARQL have been proposed to query RDF data modulo RDFS, i.e., interpreting the query with RDFS semantics and/or considering externa...

This paper studies the expressive power of SPARQL. The main result is that SPARQL and non-recursive safe Datalog with negation have equivalent expressive power, and hence, by classical results, SPARQL is equivalent from an expressive point of view to Relational Algebra. We present explicit generic rules of the transformations in both directions. Among other findings of the paper are the proof t...

The issue of subqueries in SPARQL has appeared in different papers as an extension point to the original SPARQL query language. Particularly, nested CONSTRUCT in FROM clauses are a feature that has been discussed as a potential input for SPARQL 1.1 which was resolved to be left out in favour of select subqueries under the—unproven—conjecture that such subqueries can express nested construct que...