Virtuoso questions

Categorie:Platform LOD
On april 25 2014 we had a knowledge session on Virtuoso Details virtuoso webinar on 25 april. This page contains the questions and answers.
See also: LinkedIn item: Vragen over Virtuoso voor kennisoverdracht LOD2
==Attendants==
* 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)
==Questions==
===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
**Replication
**ACL control over large numbers of graphs
*http://virtuoso.openlinksw.com/features-comparison-matrix
===Can you share your experiences with other projects that are working with the combination of Hadoop, Virtuoso and Elasticsearch, in environments with a lot of data?===
* 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 
*Pros:
**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 
*Cons: 
**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
**Point
**MultiPoint
**LineString
**MultiLineString
**Box
**Polygon
**MultiPolygon
**GeometryCollection
*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.
===How to store time related data (temporal) ?===
*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
**http://docs.openlinksw.com/virtuoso/backup.html
*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 ...