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Correlation and Substitution in SPARQL [article]

Daniel Hernández and Claudio Gutierrez and Renzo Angles
2016 arXiv   pre-print
In this technical report, we provide a semantics of correlation and substitution following the classic philosophy of substitution and correlation in logic, programming languages and SQL.  ...  In the current SPARQL specification the notion of correlation and substitution are not well defined. This problem triggers several ambiguities in the semantics.  ...  Introduction The first version of this technical report served as a starting point to restart the discussion about the substitution and correlation in SPARQL.  ... 
arXiv:1606.01441v2 fatcat:3cywi52zpffm7l6f4subh52gni

The Problem of Correlation and Substitution in SPARQL -- Extended Version [article]

Daniel Hernández and Claudio Gutierrez and Renzo Angles
2018 arXiv   pre-print
In this paper we study why different implementations of SPARQL (Fuseki, Virtuoso, Blazegraph and rdf4j) behave differently when evaluating queries with correlated variables.  ...  We show that at the core of this problem lies the historically troubling notion of logical substitution.  ...  Of course the example is highly unnatural but, as we will show, it codes the essence of the problems of substitution of correlated variables in SPARQL.  ... 
arXiv:1801.04387v2 fatcat:yxjpcs7ksve4fn724myw2grxx4

Revealing Secrets in SPARQL Session Level [article]

Xinyue Zhang, Meng Wang, Muhammad Saleem, Axel-Cyrille Ngonga Ngomo, Guilin Qi, Haofen Wang
2020 arXiv   pre-print
Answer-seekers often examine intermediate results iteratively and modify SPARQL queries repeatedly in a search session.  ...  In particular, we thoroughly assess query changes made by users w.r.t. structural and data-driven features of SPARQL queries.  ...  -We are the first, to the best of our knowledge, to investigate potential correlations between SPARQL queries and provide a comprehensive analysis of query reformulations in a given search session.  ... 
arXiv:2009.06625v2 fatcat:kjuwevbkpvckbblcqcwnllra6y

Evaluating SPARQL Subqueries over P2P Overlay Networks

Liaquat Ali, Georg Lausan
2012 2012 23rd International Workshop on Database and Expert Systems Applications  
The evaluation of subqueries in distributed environment may be very inefficient and expensive in term of query response time and bandwidth usage, particularly for the correlated subqueries, where the inner  ...  In this paper, we study the problem of evaluating SPARQL subqueries over RDF data stored in 3nuts p2p network.  ...  The existing distributed RDF systems evaluate the triple patterns topdown, and for the evaluation of a correlated query, the semantics of SPARQL query prescribe that the triples of the outer query be substituted  ... 
doi:10.1109/dexa.2012.27 dblp:conf/dexaw/AliL12 fatcat:eo2uhs2xwna2zd2sho6rliwkeu

CLASSIFICATION OF SPARQL QUERIES INTO EQUIVALENCE CLASSES OF RELEVANT QUERIES

Theodore Andronikos
2017 International Journal of Advanced Research in Computer Science  
The novel concepts of relevant queries and covering query are introduced in a manner appropriate for the study of SPARQL queries.  ...  They enable the formal identification of similar queries and this leads to the partition of SPARQL queries into equivalence classes of relevant queries.  ...  Another theoretical work that investigated the correlation of queries on RDF datasets to certain types of finite automata appeared in [10] .  ... 
doi:10.26483/ijarcs.v8i9.4940 fatcat:cozl7svn3fgejasl7gehqk67gu

Negation in SPARQL [article]

Renzo Angles, Claudio Gutierrez
2016 arXiv   pre-print
This paper presents a thorough study of negation in SPARQL. The types of negation supported in SPARQL are identified and their main features discussed.  ...  At this point, we identify a core SPARQL algebra which could be used instead of the W3C SPARQL algebra.  ...  We will use a generic operator NEG to denote any of the operators used in our analysis, i.e. DIFF and MINUS.  ... 
arXiv:1603.06053v4 fatcat:exwwk76havflldeft5ew6dbpvy

Certain Answers for SPARQL with Blank Nodes [chapter]

Daniel Hernández, Claudio Gutierrez, Aidan Hogan
2018 Lecture Notes in Computer Science  
In order to estimate the performance costs that would be associated with such a change in semantics for current implementations, we adapt and evaluate approximation techniques proposed in a relational  ...  However, while SPARQL considers blank nodes in a query as existentials, it treats blank nodes in RDF data more like constants.  ...  Acknowledgements The work was also supported by the Millennium Institute for Foundational Research on Data (IMFD) and by Fondecyt Grant No. 1181896.  ... 
doi:10.1007/978-3-030-00671-6_20 fatcat:imtlfngijzaqtj2fml6cmno6ay

Cardinality estimation for the optimization of queries on ontologies

E. Patrick Shironoshita, Michael T. Ryan, Mansur R. Kabuka
2007 SIGMOD record  
Experimental analysis has shown that the algorithm produces estimates with high accuracy and with high correlation to actual values.  ...  In order to estimate the total number of result set parameters for each path, a set of statistics is compiled on the properties of the ontology.  ...  Thomas Taylor and Dr. Akmal Younis of INFOTECHSoft, Inc.  ... 
doi:10.1145/1328854.1328856 fatcat:sjx46e6tjbh2ffhzq5tvehgyhm

SPBERT: An Efficient Pre-training BERT on SPARQL Queries for Question Answering over Knowledge Graphs [article]

Hieu Tran, Long Phan, James Anibal, Binh T. Nguyen, Truong-Son Nguyen
2021 arXiv   pre-print
By incorporating masked language modeling objectives and the word structural objective, SPBERT can learn general-purpose representations in both natural language and SPARQL query language.  ...  In this paper, we propose SPBERT, a transformer-based language model pre-trained on massive SPARQL query logs.  ...  This method is highly correlated with our approach, so we treat this work as our baseline later in this paper.  ... 
arXiv:2106.09997v2 fatcat:6k2ids2m4faglbj5nmrmwiqliu

Extending SPARQL Algebra to Support Efficient Evaluation of Top-K SPARQL Queries [chapter]

Alessandro Bozzon, Emanuele Della Valle, Sara Magliacane
2012 Lecture Notes in Computer Science  
In this paper, we present SPARQL-RANK, an extension of the SPARQL algebra and execution model that supports ranking as a first-class SPAR-QL construct.  ...  Top-k queries can be expressed in SPARQL by appending to a SELECT query the ORDER BY and LIMIT clauses, which impose a sorting order on the result set, and limit the number of results.  ...  in SPARQL.  ... 
doi:10.1007/978-3-642-34213-4_10 fatcat:l4v2yejsvnavfmljimpb2ovsja

A Machine Learning Approach to SPARQL Query Performance Prediction

Rakebul Hasan, Fabien Gandon
2014 2014 IEEE/WIC/ACM International Joint Conferences on Web Intelligence (WI) and Intelligent Agent Technologies (IAT)  
We show how to model SPARQL queries as feature vectors, and use k-nearest neighbors regression and Support Vector Machine with the nu-SVR kernel to accurately predict SPARQL query execution time.  ...  In this paper we address the problem of predicting SPARQL query performance. We use machine learning techniques to learn SPARQL query performance from previously executed queries.  ...  The edit operations are deletions, insertions, and substitutions of nodes and edges.  ... 
doi:10.1109/wi-iat.2014.43 dblp:conf/webi/HasanG14 fatcat:ra4xpxe4yba5fe3cr2cd3fmi64

FedX: Optimization Techniques for Federated Query Processing on Linked Data [chapter]

Andreas Schwarte, Peter Haase, Katja Hose, Ralf Schenkel, Michael Schmidt
2011 Lecture Notes in Computer Science  
In experiments, we demonstrate the practicability and efficiency of our framework on a set of real-world queries and data sources from the Linked Open Data cloud.  ...  We propose novel join processing and grouping techniques to minimize the number of remote requests, and develop an effective solution for source selection in the absence of preprocessed metadata.  ...  Research reported in this paper was partially supported by the German BMBF in the project CollabCloud. http://collabcloud.de/  ... 
doi:10.1007/978-3-642-25073-6_38 fatcat:3mgfop65s5dmbpmkterq4j2hve

Distributed Semantic Web Data Management in HBase and MySQL Cluster

Craig Franke, Samuel Morin, Artem Chebotko, John Abraham, Pearl Brazier
2011 2011 IEEE 4th International Conference on Cloud Computing  
In particular, we design distributed RDF data storage and querying schemes for HBase and MySQL Cluster and conduct an empirical comparison of these approaches on a cluster of commodity machines using datasets  ...  In this work, we study and compare two approaches to distributed RDF data management based on emerging cloud computing technologies and traditional relational database clustering technologies.  ...  More details on SPARQL features and semantics can be found in the W3C's SPARQL specification.  ... 
doi:10.1109/cloud.2011.19 dblp:conf/IEEEcloud/FrankeMCAB11 fatcat:c73umymenvfhri5dqadjx2y25e

Heuristics-based query optimisation for SPARQL

Petros Tsialiamanis, Lefteris Sidirourgos, Irini Fundulaki, Vassilis Christophides, Peter Boncz
2012 Proceedings of the 15th International Conference on Extending Database Technology - EDBT '12  
We present these in the context of a new Heuristic SPARQL Planner (HSP) that is capable of exploiting the syntactic and the structural variations of the triple patterns in a SPARQL query in order to choose  ...  The more profound reason is that due to the absence of schematic structure in RDF, join-hit ratio estimation requires complicated forms of correlated join statistics; and currently there are no methods  ...  , and avoids the false sense of precision of relying on purely relational cost-based methods (which fail to capture joinselection correlations prevalent in SPARQL queries); b) rather than relying on partial  ... 
doi:10.1145/2247596.2247635 dblp:conf/edbt/TsialiamanisSFCB12 fatcat:onpf27gmvndabivryphmeczcse

S2RDF

Alexander Schätzle, Martin Przyjaciel-Zablocki, Simon Skilevic, Georg Lausen
2016 Proceedings of the VLDB Endowment  
We demonstrate its superior performance in comparison to state of the art SPARQL-on-Hadoop approaches.  ...  Our prototype system S2RDF is built on top of Spark and uses SQL to execute SPARQL queries over ExtVP.  ...  Two triple patterns in a SPARQL query that are connected by an OO correlation often use the same predicates (cf. OO in Figure 2 ) and thus result in a selfjoin of the corresponding VP table.  ... 
doi:10.14778/2977797.2977806 fatcat:kehcu2c43rhczorh4nl7vkxlwu
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