Matches in ScholarlyData for { ?s ?p ?o. }
- authorList hasItem item-1.
- authorList hasItem item-2.
- authorList hasLastItem item-2.
- item-1 type ListItem.
- item-1 hasContent sebastian-wandelt.
- item-1 next item-2.
- item-2 type ListItem.
- item-2 hasContent ralf-moeller.
- item-2 previous item-1.
- 4 creator andreas-harth.
- 4 creator guenter-ladwig.
- 4 type InProceedings.
- 4 label "CumulusRDF: Linked Data Management on Nested Key-Value Stores".
- 4 sameAs 4.
- 4 abstract "SAQ (Semantic Archive and Query) is a system for long-term preservation and querying of relational data in terms of RDF. In SAQ relational data in a back-end DBMS is exposed as an RDF view, called the RD-view. SAQ can process arbitrary SPARQL queries to the RD-view. Long-term preservation as RDF of selected parts of a relational database is specified by SPARQL queries to the RD-view. Such queries usually select sets of RDF properties and thus in the query definition a property p is unknown. We call such queries unbound-property queries. This class of queries is also present in the SPARQL benchmarks. We optimize unbound-property queries by introducing a query transformation algorithm called Group Common Terms, GCT. It pulls out from a DNF normalized query those common terms that can be translated to SQL predicates accessing the relational database. Our experiments using the Berlin SPARQL benchmark show that GCT improves substantially the query execution time to a back-end commercial relational DBMS for both selective and unselective unbound-property queries. We compared the performance of our approach with the performance of other systems processing SPARQL queries over views of relational databases and showed that GCT improves scalability compared to the approaches used by the other systems. ".
- 4 hasAuthorList authorList.
- 4 isPartOf proceedings.
- 4 keyword "distributed storage".
- 4 keyword "indexing".
- 4 keyword "linked data".
- 4 keyword "triple store".
- 4 title "CumulusRDF: Linked Data Management on Nested Key-Value Stores".
- authorList type List.
- authorList hasFirstItem item-1.
- authorList hasItem item-1.
- authorList hasItem item-2.
- authorList hasLastItem item-2.
- item-1 type ListItem.
- item-1 hasContent guenter-ladwig.
- item-1 next item-2.
- item-2 type ListItem.
- item-2 hasContent andreas-harth.
- item-2 previous item-1.
- 5 creator achille-fokoue.
- 5 creator jeff-z-pan.
- 5 creator mudhakar-srivatsa.
- 5 creator murat-sensoy.
- 5 type InProceedings.
- 5 label "Probabilistic Abox Abduction in Description Logics".
- 5 sameAs 5.
- 5 abstract "In recent years, there has been an explosion of publicly availableSemantic Web data. In order to effectively integrate millions ofsmall, distributed data sources and quickly answer queries, we previouslyproposed a tree structure query optimization algorithm that takes thesource selectivity of each query subgoal as the heuristic to plan the queryexecution and uses the most selective subgoals to provide constraintsthat make other subgoals selective. However, this constraint propagationis incomplete when the relevant ontologies contain cyclic axioms. Here,we propose an improvement to this algorithm that is complete for cyclicaxioms, yet still able to scale to millions of data sources.".
- 5 hasAuthorList authorList.
- 5 isPartOf proceedings.
- 5 keyword "Abductive Reasoning".
- 5 keyword "DL-lite".
- 5 keyword "SHIQ".
- 5 keyword "Semantic Web".
- 5 title "Probabilistic Abox Abduction in Description Logics".
- authorList type List.
- authorList hasFirstItem item-1.
- authorList hasItem item-1.
- authorList hasItem item-2.
- authorList hasItem item-3.
- authorList hasItem item-4.
- authorList hasLastItem item-4.
- item-1 type ListItem.
- item-1 hasContent murat-sensoy.
- item-1 next item-2.
- item-2 type ListItem.
- item-2 hasContent achille-fokoue.
- item-2 next item-3.
- item-2 previous item-1.
- item-3 type ListItem.
- item-3 hasContent mudhakar-srivatsa.
- item-3 next item-4.
- item-3 previous item-2.
- item-4 type ListItem.
- item-4 hasContent jeff-z-pan.
- item-4 previous item-3.
- 6 creator silvia-stefanova.
- 6 creator tore-risch.
- 6 type InProceedings.
- 6 label "Optimizing Unbound-property Queries to RDF Views of Relational Databases".
- 6 sameAs 6.
- 6 abstract "Quad stores have a number of features that make them very attractive for Semantic Web applications. Quad stores use Named Graphs to give contextual information to RDF graphs. Developers can use these contexts to incorporate meta-data such as provenance and versioning. The OWL language specification provides the owl:imports construct as one of the key ways to reuse the ontologies on the Semantic Web. When one ontology imports another through the owl:imports statement, all axioms from the imported ontology are brought to the source ontology. When implementing an online ontology repository, we have explored a number of different approaches to reflect these imports and contextual information in a quad store. These approaches have a direct impact on storage requirements, query articulation, and reusability.This paper describes different models to represent contextual information, ontology imports and versioning. We have performed the experiments in the context of storing ontologies from the BioPortal ontology repository. This repository has 304 ontologies, and multiple versions for many of them. We extract metrics on the levels of imports, and the storage and performance requirements and discuss the trade-offs between query articulation, reusability and scalability.".
- 6 hasAuthorList authorList.
- 6 isPartOf proceedings.
- 6 keyword " unbound property queries".
- 6 keyword "RDF views of relational databases".
- 6 keyword "SPARQL queries".
- 6 keyword "query optimization".
- 6 keyword "query rewrites".
- 6 title "Optimizing Unbound-property Queries to RDF Views of Relational Databases".
- authorList type List.
- authorList hasFirstItem item-1.
- authorList hasItem item-1.
- authorList hasItem item-2.
- authorList hasLastItem item-2.
- item-1 type ListItem.
- item-1 hasContent silvia-stefanova.
- item-1 next item-2.
- item-2 type ListItem.
- item-2 hasContent tore-risch.
- item-2 previous item-1.
- 7 creator giorgos-stamou.
- 7 creator giorgos-stoilos.
- 7 creator tassos-venetis.
- 7 type InProceedings.
- 7 label "Query Rewriting Under Query Extensions for OWL 2 QL Ontologies".
- 7 sameAs 7.