Use Virtuoso instead of GraphDB as triplestore

[vemonet]

Use Virtuoso webDAV to easily upload RDF files through HTTP.

We might need to play around with the configuration as Virtuoso current version (7) does not include LDP capabilities out-of-the-box

• LDP docs: http://vos.openlinksw.com/owiki/wiki/VOS/VirtLDP#What%20is%20the%20Linked%20Data%20Platform%20%28LDP%29%3F
• cf. discussion to solve it https://community.openlinksw.com/t/permissions-on-ldp-containers-and-resources/290/9
• GitHub issue: https://github.com/openlink/virtuoso-opensource/issues/466
• Download VAD packages: http://download3.openlinksw.com/index.html?prefix=uda/vad-vos-packages/7.2/

GitHub repo with some instructions to enable LDP in Virtuoso: https://github.com/markwilkinson/to_build_virtuoso_ldp With the corresponding image on DockerHub: https://hub.docker.com/r/markw/ldp_server

Note: delete a file from the webDAV with iSQL

select DB.DBA.DAV_DELETE ('/DAV/home/dba/rdf_sink/gitee.ttl', 0, 'dba', 'dba');

Trying with current Virtuoso deployment

Create a folder:

curl -iX PUT -u dav:password -H 'Content-Type: text/turtle' https://data.index.semanticscience.org/DAV/home/dav/rdf_sink/test-folder

Upload with HTTP:

curl --verbose -iX PUT -F "data=@shapes-rdf.ttl" -u dav:password -H 'Content-Type: text/turtle' https://data.index.semanticscience.org/DAV/home/dav/rdf_sink/shapes-of-you.ttl

Error (even if the prefix is properly define in the file):

<p>TURTLE RDF loader, line 6: SP029: TURTLE RDF loader, line 6: Undefined namespace prefix at ns1:EntryPoint</p>%

[vemonet]

Using Virtuoso greatly increase the response time (from 10s to ~30s), and updating the GraphDB triplestore is easier that the Virtuoso LDP. So we will keep using GraphDB