Discuss Using SPARQL and RDF stores

Talk pages on this wiki should primarily be used to address possible mistakes as well as missing and superseded information in the documentation.
In case you are seeking support concerning individual questions, please have a look at this page. The Semantic MediaWiki user mailing list is always a good idea for seeking help.

Known Limitations

• Category and property hierarchies: Hierarchies are only taken into account if the RDF database has built-in support for the rdfs:subClassOf and rdfs:subPropertyOf features of RDF Schema. Otherwise hierarchy information will not lead to additional query results.
  • Do 4Store and Virtuoso support those features? --Dan Bolser 10:16, 3 August 2011 (CEST)

Pros and Cons of Using an RDF Database

• Reasoning features and Ontology Based Data Access: Semantic Web languages such as RDF Schema and OWL provide additional expressive features for modeling, for example by allowing the declaration of derived classes or the declaration of further property characteristics (e.g. transitivity of properties). Some SPARQL-capable databases can evaluate these features for query answering, e.g. for Ontology Based Data Access (the method of creating "virtual views" on data by means of semantic modeling constructs).

Is this a pro or a con? It isn't clear what is meant here, or, more specifically, how this relates to SMW. --Dan Bolser 10:34, 3 August 2011 (CEST)

Which RDF Database to Use

"As of 2011, two particularly notable free and open source RDF databases are 4Store and Virtuoso. Both have been used with SMW successfully, though Virtuoso currently still needs minor changes in SMW due to the aforementioned restriction that no named graphs are used in SMW queries."

Could you please specify which particular configurations in SMW are required to make virtuoso work with SMW?

Hi, I suggest to use the mailing list, since the chance to get advice on this is significantly higher there. Cheers --[[kgh]] 23:42, 26 October 2011 (CEST)

Configuring SMW

It seems that the advice to edit the LocalSettings.php file is incorrect. Are these settings not in [SemanticMediaWiki]/SMW_Settings.php ?

[SemanticMediaWiki]/SMW_Settings.php contains the defaults - you should NOT edit this file (it will be overwritten at the next SMW upgrade anyway!), but "override" them in LocalSettings.php. The texts are therefor correct. --Jan "Saruman!" S. 22:16, 30 May 2012 (CEST)

You need the curl extension to PHP for 4Store integration (and probably Virtuoso too) to work. If you are on Debian/Ubuntu, use

sudo apt-get install php5-curl

Alex (talk)