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Efficient Handling of SPARQL OPTIONAL for OBDA
Published on Nov 22, 20182854 Views
OPTIONAL is a key feature in SPARQL for dealing with missing information. While this operator is being used extensively, it is also known for its complexity, which can make it challenge to evaluate qu
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Efficient Handling of SPARQL OPTIONAL for OBDA00:00
NULL values are ubiquitous in relational databases - 100:19
NULL values are ubiquitous in relational databases - 200:24
RDF graph: no NULL value - 100:48
RDF graph: no NULL value - 201:22
LEFT JOIN: NULL values produced by the query - 102:26
LEFT JOIN: NULL values produced by the query - 202:40
LEFT JOIN: NULL values produced by the query - 303:04
Ontology-Based Data Access (OBDA) - 103:21
Ontology-Based Data Access (OBDA) - 204:06
Excessive use of the padding effect - 105:19
Excessive use of the padding effect - 205:33
Excessive use of the padding effect - 306:05
Excessive use of the padding effect - 406:19
Excessive use of the padding effect - 506:38
Weakly well designed query (preferences) - 106:54
Weakly well designed query (preferences) - 207:43
Weakly well designed query (preferences) - 308:00
Why are novel optimisations needed? - 108:30
Why are novel optimisations needed? - 210:17
Why are novel optimisations needed? - 310:46
Contribution11:22
SPARQL to SQL translation11:42
Optimisations of translated queries12:17
Evaluation13:54
Evaluation results (in seconds)14:47
Conclusions15:45