Description

The SPARQL Entity Storage module offers a SPARQL backend for Drupal entities. The module provides an entity storage and query. Simply enabling the module, doesn't bring any user visible new feature, the module is a prerequisite for other modules that are defining Drupal entities that requires a SPARQL triple-store backend. A very simple example of such an entity is the sparql_test entity provided in the SPARQL Test testing module, included in this package (see the SparqlTest class). A more sophisticated module that uses the SPARQL backend, and runs already in the wild, is the RDF Entity module. The entity provided there (rdf_entity) can be used as it is, can be extended or, simply, used as an example when designing a new entity type.

Getting started

A working SPARQL endpoint is needed. You could either use a remote SPARQL endpoint, or you could set one up locally. Virtuoso is one of the more robust triple store solutions available, but any solution would do.

@todo Create an example module that uses http://dbpedia.org/sparql

Setting up Virtuoso

On a Debian based system

apt-cache search "^virtuoso" will show you available packages.

$ apt-get install virtuoso-opensource
$ service virtuoso-opensource-6.1 start

(Set the password during installation)

On a MacOS system

• Install Homebrew (see http://brew.sh)
• $ brew install virtuoso
• Start Virtuoso

  # The version might be differnet than 7.2.4.2.
  $ cd /usr/local/Cellar/virtuoso/7.2.4.2/var/lib/virtuoso/db
  $ virtuoso-t -f &
  

• Administer at http://localhost:8890/conductor/. Login with dba/dba.

On an Arch Linux based system

• Install the Virtuoso AUR package.
• # systemctl start virtuoso

Go to http://localhost:8890/conductor/ and login in with: dba - yourpass.

• Grant 'update' rights to the SPARQL user:
• System admin -> Users -> SPARQL (edit)
• Account roles -> Put SPARQL_UPDATE in 'Selected'

Connecting Drupal to the SPARQL endpoint

The following example demonstrates the use with a local Virtuoso installation. To connect Drupal to the endpoint, the db connection should be added to the settings.php file.

$databases['sparql_default']['sparql'] = [
  'prefix' => '',
  'host' => '127.0.0.1',
  'port' => '8890',
  'namespace' => 'Drupal\\Driver\\Database\\sparql',
  'driver' => 'sparql',
  // Optional. This is actually the endpoint path. If omitted, 'sparql' will
  // be used.
  'database' => 'data/endpoint',
  // If the connection to the endpoint should be HTTPS secured. If omitted,
  // FALSE is assumed.
  'https' => FALSE,
];

Content translation

Entities using SPARQL storage support basic content translations. This is still WIP.

Note: If content translations are enabled, the 'langcode' property must be mapped, otherwise entity reference fields will not store information.