On april 25 2014 we had a knowledge session on Virtuoso Details virtuoso webinar on 25 april. This page contains the questions and answers.
- Martin Kaltenböck (Semantic Web Company, LOD2 PUBLINK)
- Hugh Williams (OpenLink Software)
- Patrick van Kleef (OpenLink Software)
- Gerard Persoon (PiLOD Platform,GerardPersoonBV)
- Richard Nagelmaeker (PiLOD Platform, Ordina)
- Pieter van Everdingen (PiLOD Wiki, OpenInc)
- Rein van 't Veer (Digital Heritage)
How to show RDF resources when accessed by their own URI
- VIa the HTML proxy description service (/about/html) or the Virtuoso Faceted Browser service (/describe). http://virtuoso.openlinksw.com/dataspace/doc/dav/wiki/Main/VirtFacetBrowserInstallConfig
- OpenLink public Sponger service: http://uriburner.com
- OpenLink public Faceted Browser: http://uriburner.com/fct
- OpenLink LOD Cloud CacheServer (60+ billion triples): http://lod.openlinksw.com
- RDF HTML description of sponged PiLOD Web Page: http://bit.ly/1jIanPE
- Faceted Browser results page of sponged PiLOD Web Page: http://bit.ly/1tI28Lw
- Virtuoso Linked Data Deployment Guide for Generic URI naming scheme creation http://virtuoso.openlinksw.com/dataspace/doc/dav/wiki/Main/VirtDeployingLinkedDataGuide
What are the differences between the open source and the closed source version of Virtuoso?
- The main differences are the following which are closed source only:
- Clustering & High Availability
- Virtual Database
- ACL control over large numbers of graphs
- Most implementation we come across in the Enterprise are using Virtuoso as the RDF Quad Store for indexing of Meta Data in conjunction with a combination of Hadoop, Elasticsearch, Lucense/Solr , Key Value (No-SQL) database and traditional relational databases.
- Example Elsevier http://www.slideshare.net/ayagoda/elsevier-smart-content-ldr-sem-tech-2012-v4 Smart Content Linked Data Repository
Is the new LOD2 ETL tool Unified Views an open source tool that can be used within the PiLOD platform to get Hadoop data into an Virtuoso environment?
- Unified Views is open source and will be part for the final LOD2 Stack release https://grips.semantic-web.at/display/UDDOC/Introduction
- There was a LOD2 Webinar on Unified Views earlier this month
- Don’t see anything specifically about Hadoop support but I would imagine hadoop jobs can be defined in its processing pipeline for invocation in processing data (large), which once processed and transformed to RDF can be store in Virtuoso as a support triple store in the LOD2 Stack
What are the typical use cases for Virtuoso Sponger? And what are the differences, pros and cons compared to other RDF middleware?
- The Virtuoso Sponger Middleware is used for the transformation of structured and unstructured web accessible resources to RDF Linked Data, using a combination of extractor (transformers)and(enrichment) cartridges. http://virtuoso.openlinksw.com/dataspace/doc/dav/wiki/Main/VirtSponger
- Cartridges can be written with its programmable API http://virtuoso.openlinksw.com/dataspace/doc/dav/wiki/Main/VirtSpongerCartridgeProgrammersGuide
- Automatically integrated with Virtuoso Quad Store
- 200+ Cartridges already exist and are provided with Virtuoso
- List of available Sponger Cartridges http://virtuoso.openlinksw.com/dataspace/doc/dav/wiki/Main/VirtSpongerCartridgeSupportedDataSources
- Aperture cartridge for PDF and Powerpoint http://virtuoso.openlinksw.com/dataspace/doc/dav/wiki/Main/RDFMapper
- Cannot be used with other triple stores
- Currently working in Fusepool P3 project on decoupling the Virtuoso sponger from the Quad Store and also to make it a more flexible RDF ETL processing pipeline
What are best practices to convert RDBMS data to RDF data?
- Virtuoso RDF Linked Data Views http://virtuoso.openlinksw.com/dataspace/doc/dav/wiki/Main/VOSSQL2RDF
- Virtuoso R2RML support http://virtuoso.openlinksw.com/dataspace/doc/dav/wiki/Main/VirtR2RML
- D2R Server which is part of the LOD2 Stack http://lod2.eu/Project/D2R-Server.html
- Hand crafted scripts/programs for mapping Relational Data to RDF Datasets
- DB2Triples already being used by one of the PiLOD platform users https://github.com/antidot/db2triples/
What are the possibilities with Geodata in Virtuoso 7.1?
- The following GeoSpatial data types are supported along with associated geometries
- Update to Virtuoso RDF Geometry documentation being prepared http://docs.openlinksw.com/virtuoso/rdfsparqlgeospat.html
- Virtuoso SPARQL Extensions for Geo Spatials Geography Tutorial http://virtuoso.openlinksw.com/tutorials/sparql/SPARQL_Tutorials_Part_10/SPARQL_Tutorials_Part_10.html#(1)
- Virtuoso SPARQL Geo Spatials and Geography PivotViewer Examples http://virtuoso.openlinksw.com/tutorials/sparql/SPARQL_Tutorials_Part_11/SPARQL_Tutorials_Part_11.html#(1)
What are the known issues with Geo data support in Virtuoso 7.1 and what is the schedule and priority to resolve those issues?
- Working on full OGC compliance http://www.opengeospatial.org/
- Working on full GeoSPARQL compliance http://www.geosparql.org/
- Both as part of our involvement in the GeoKnow project, see GeoKnow D2.3.1 deliverable http://svn.aksw.org/projects/GeoKnow/Public/D2.3.1_Prototype_of_Built-in_Geospatial_Capabilities.pdf
- GeoKnow ends in 1.5 years time so would expect to have full compliance by then, but hope to be well before that http://geoknow.eu
Which parties are also interested in Geo Data?
- We are also working with other Geo Data specialist who are interested in Linked Geo Data support to ensure the implementation is right. http://www.w3.org/2014/03/lgd/
- See list of attendees in Linked Geo Data workshop 2014 in London for interested parties http://www.w3.org/2014/03/lgd/
- Ordinance Survey http://data.ordnancesurvey.co.uk/UK
- Digital Heritage Netherlands http://www.ldbc.eu:8090/download/attachments/5538064/Presentation+LDBC+Heritage+%26+Location.pptx?version=1modificationDate=1396604660000
- Geodan NL http://www.ldbc.eu:8090/download/attachments/5538064/Presentatie+LDBC+CWI+2014-04-03.pptx?version=2modificationDate=1396604384000
- many more … http://www.w3.org/2014/03/lgd/attendees
- Interesting paper on PiLOD Web site entitled, From Geo-Data to Linked Data: Automated Transformation from GML to RDF Boek/BrinkEtAl-GML2RDF
- GeoKnow Generator is a tool for transforming Geo Data to RDF Linked Data http://generator.geoknow.eu
- Based on LOD2 Stack which GeoKnow project will take over the maintenance of when LOD2 project ends this year.
- No built in support for temporal data per say
- time series data can be encoded as triple in the graph
- Using a semantic approach for monitoring applications semantic approach for monitoring applications http://www.ldbc.eu:8090/download/attachments/5538064/Virtuoso+in+PMS+Coentunnel+-+Bastiaan+Bijl.pdf?version=1modificationDate=1396597958000i
- Need to dig out examples on performed comparison operations on queries with datetime elements ...
What would be your reading recommendation for the Virtuoso documentation?
- Presentations http://www.slideshare.net/rumito/virtuoso-universal-server-overview-presentation
- Tutorials http://demo.openlinksw.com/tutorial/
- Tips and Tricks http://virtuoso.openlinksw.com/dataspace/doc/dav/wiki/Main/VirtTipsAndTricksGuide
- Mailing list http://virtuoso.openlinksw.com/dataspace/doc/dav/wiki/Main/VOSMailingLists
- Support Forums http://boards.openlinksw.com/support
What are best practices to run the server?
- how to monitor availability
- sys_stat function http://docs.openlinksw.com/virtuoso/fn_sys_stat.html
- can be hooked into Network resource monitoring tools like Zabbix or protocols like SNMP
- how to make backups
- Full support for online and incremental backup and restore
- how to optimize the server / queries
- Database Performance Tuning Guide http://docs.openlinksw.com/virtuoso/ptune.html
- RDF Performance Tuning Guide http://virtuoso.openlinksw.com/dataspace/doc/dav/wiki/Main/VirtRDFPerformanceTuning
- Key requirement is to have database workset in memory, as accessing disk will always reduce performance
- how to secure a graph for a specific user or usergroup
- RDF Graph Groups http://virtuoso.openlinksw.com/dataspace/doc/dav/wiki/Main/VirtRDFGraphsSecurity
- Access Control Lists (ACLs) http://docs.openlinksw.com/virtuoso/wsacl.html
- how to upgrade to newer versions without losing data
- ensure Full backup in place
- generally any v7.x DB will work with 7.x binary
- ensure database checkpointed before shutting down
- v6 database can be automatically upgrade to v7
- Would be in row store mode though
- Probably should dump data and reload to get column store RDF tables which consumes a third of the space/memory which is key benefit ...