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Querying the Web of Data
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Tecnologia
Presentation at the Knowledge Systems course of the UvA (December 2010)
Rinke HoekstraSeguir
Postdoctoral Researcher em VU University Amsterdam/University of AmsterdamAnúncio
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Querying the Web of Data
- `Metadata’ for web pages
- Since ~2006
- `Web of Data’
- Semantic web as data source in its own right
- Linked Data
- A ‘Databaseesque’ Web
- RDF Triple stores
- Realtime vs. in advance
- Lightweight reasoning (RDFS, OWL 2 RL)
- Implementable using forward chaining rules
- Still problems with scalability
- Distributed reasoning (DAS-3)
- MaRVIN
- ‘SpeedDate’ distrubution of triples across nodes
- MapReduce
- Full closure of BTC in 57 minutes
- Output: 30B triples
- Load time
- … a couple of hours
- Simple table lookup (one-variable query)
- … about 5 minutes
- Single join (two-variable query)
- … a couple of hours
- Better indexes?
- Harddisk access times are the bottleneck (9ms)
- RDF, RDFS and OWL
- Triples <subject, predicate,object>
- Distributed
- Always about something else
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