Development/Tutorials/Metadata/Nepomuk/StorageService

Nepomuk Storage Service

Tutorial Series	Nepomuk
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What's Next	OntologyLoader
Further Reading	Nepomuk Services, Nepomuk Server

Nepomuk Storage Service

The main repository is an RDF database using Soprano including a Soprano full text index. The interface of the repository is exported via DBus (The DBus interface is defined by Soprano). When using the Soprano DBus interface from within a KDE application there is no need to bother with QDBus. Soprano provides the Soprano::Client::DBusModel class which wraps all DBus communication into a nice Soprano::Model interface.

There are two ways to access this wrapper model:

1. Use Soprano::Client::DBusClient to create a connection to the Nepomuk Server:

<syntaxhighlight lang="cpp-qt"> Soprano::Client::DBusClient* client = new Soprano::Client::DBusClient( "org.kde.NepomukStorage" ); Soprano::Model* model = client->createModel( "main" );

The Nepomuk Server registers as DBus service org.kde.NepomukStorage and the name of the main data repository is main.

2. Use the Nepomuk library, i.e. ResourceManager to access the main model:

<syntaxhighlight lang="cpp-qt"> Soprano::Model* model = Nepomuk::ResourceManager::instance()->mainModel();

The advantage of the first version is that there is no need to link to libnepomuk. On the other hand the main model as provided by libnepomuk connects via a local socket if available which is faster. Also, it provides an automatic re-connect feature. When implementing a Nepomuk service use Service to access the main repository:

<syntaxhighlight lang="cpp-qt"> class MyService : public Nepomuk::Service { public:

   MyService( QObject* parent ) : Service( parent ) {
      Soprano::Model* model = mainModel();
   }

};

So all in all the easy way is also the recommended one: use libnepomuk and the ResourceManager or Service to access the data.