I’m working on an institutional project and we use Omeka-s as CMS. We devised some domain-specific ontologies that we imported into Omeka-s as vocabularies. We already populated the DB using Omeka-s templates and REST API, following the schema provided by the ontologies we developed.
Due to the project’s goal and complexity, we cannot use Omeka-s site for data retrieval and visualization. Instead, we use a custom web app that directly queries the RDB beneath Omeka-s and displays items following the structures provided by templates.
As a final goal, we want to query Omeka through SPARQL. However, I cannot find any solution by looking at various available modules and other topics in this forum.
Does anyone have some tips or suggestions on how it can be possible to use SPARQL to query (only retrieve and display, not insert) data stored in Omeka-s?
It is not possible to use SPARQL to query the Omeka S database. To do so would require migrating data from Omeka’s relational database to an RDF graph database or triplestore. I am unaware of any efforts to do this, but perhaps someone who has tried can follow up here.
I personally just harvest all JSON-LD (which is RDF!!) via the standard Omeka S REST API with a simple harvester which you can then import into a SPARQL enabled triplestore like Apache Jena Fuseke or GraphDB. You can read about this in the Google-translated article Under the hood: providing linked open data via SPARQL endpoint on the Gouda Timemachine website.