Minimal probing: supporting expensive predicates for top-k queries
Proceedings of the 2002 ACM SIGMOD international conference on Management of data
Evaluating Top-k Queries over Web-Accessible Databases
ICDE '02 Proceedings of the 18th International Conference on Data Engineering
SIGMOD '04 Proceedings of the 2004 ACM SIGMOD international conference on Management of data
SemRank: ranking complex relationship search results on the semantic web
WWW '05 Proceedings of the 14th international conference on World Wide Web
RankSQL: query algebra and optimization for relational top-k queries
Proceedings of the 2005 ACM SIGMOD international conference on Management of data
Probe Minimization by Schedule Optimization: Supporting Top-K Queries with Expensive Predicates
IEEE Transactions on Knowledge and Data Engineering
Supporting top-K join queries in relational databases
VLDB '03 Proceedings of the 29th international conference on Very large data bases - Volume 29
Sum-max monotonic ranked joins for evaluating top-k twig queries on weighted data graphs
VLDB '07 Proceedings of the 33rd international conference on Very large data bases
SPARQL basic graph pattern optimization using selectivity estimation
Proceedings of the 17th international conference on World Wide Web
A survey of top-k query processing techniques in relational database systems
ACM Computing Surveys (CSUR)
Semantics and complexity of SPARQL
ACM Transactions on Database Systems (TODS)
Optimal algorithms for evaluating rank joins in database systems
ACM Transactions on Database Systems (TODS)
Foundations of SPARQL query optimization
Proceedings of the 13th International Conference on Database Theory
f-SPARQL: a flexible extension of SPARQL
DEXA'10 Proceedings of the 21st international conference on Database and expert systems applications: Part I
Semantics and optimization of the SPARQL 1.1 federation extension
ESWC'11 Proceedings of the 8th extended semantic web conference on The semanic web: research and applications - Volume Part II
Querying the semantic web with preferences
ISWC'06 Proceedings of the 5th international conference on The Semantic Web
A general framework for representing, reasoning and querying with annotated Semantic Web data
Web Semantics: Science, Services and Agents on the World Wide Web
Efficiently joining group patterns in SPARQL queries
ESWC'10 Proceedings of the 7th international conference on The Semantic Web: research and Applications - Volume Part I
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With the widespread adoption of Linked Data, the efficient processing of SPARQL queries gains importance. A crucial category of queries that is prone to optimization is "top-k" queries, i.e. queries returning the top k results ordered by a specified ranking function. 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. However, the ORDER BY and LIMIT clauses in SPARQL algebra are result modifiers, i.e. their evaluation is performed only after the evaluation of the other query clauses. The evaluation of ORDER BY and LIMIT clauses in SPARQL engines typically requires the process of all the matching solutions (possibly thousands), followed by a monolithically computation of the ranking function for each solution, even if only a limited number (e.g. K=10) of them were requested, thus leading to poor performance. In this paper, we present $\mathcal{S}$PARQL-$\mathcal{R}{\rm ANK}$, an extension of the SPARQL algebra and execution model that supports ranking as a first-class SPAR-QL construct. The new algebra and execution model allow for splitting the ranking function and interleaving it with other operations. We also provide a prototypal open source implementation of $\mathcal{S}$PARQL-$\mathcal{R}{\rm ANK}$ based on ARQ, and we carry out a series of preliminary experiments.