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Guest Talk: Sage: Web Preemption for Public SPARQL Query Services

Dr. Hala Skaf-Molli 

Date/Time: 12.12.2018, 15:30 

Location: TC.4.18 


After a short representation of the research topics of GDD team of the University of Nantes. I will present our ongoing research on Sage: Web Preemption for Public SPARQL Query Services. To preserve the availability of SPARQL query services, data providers enforce quotas on server usage. Queries which exceed these quotas are interrupted and delivers partial results. Such interruption is not an issue if it is possible to resume the query execution afterward. Unfortunately, there is no preemption model for the web that allows suspending and resume SPARQL queries. In this talk, I will present a model for Web preemption and Sage, a SPARQL query service that supports such preemption. SPARQL queries are suspended by the web server after a fixed time quantum and resumed upon client request. Web preemption is tractable only if its cost in time is negligible compared to the time quantum. Thus, the challenge is to support full SPARQL query language while keeping the cost of preemption negligible. Extensive experimentations demonstrate that sage outperforms existing approaches by several orders of magnitude in term of average total query execution time, time for first results and data transferred per query. 


Dr. Skaf-Molli associate professor, HDR [1] at the University of Nantes and member of the GDD Team [2] at LS2N [3]. Dr. Skaf-Molli works on decentralized semantic data management: semantic data synchronization, federated SPARQL query processing, and Servers/ Clients collaboration for executing SPARQL




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