Projects/Nepomuk/QuickStart

Nepmuk Quickstart

Tutorial Series	Nepomuk
Previous	None
What's Next	Handle Resource Metadata with Nepomuk
Further Reading	n/a

Nepomuk Quickstart

Reading or setting simple metadata in your own application can be very easy. But keep in mind that the process described here does not make much sense in terms of performance when changing a lot of metadata. We will now take a look at a simple way to access a resource's metadata.

Initializing the Resource Manager

The ResourceManager is the central KMetaData configuration point. After KDE 4.2 we must explicitly initialize it, so it connects to the Nepomuk service.

Nepomuk::ResourceManager::instance()->init();

This method returns a bool. If it's true, the connection to the Nepomuk service is stablished and we can work with it. If it's false, we couldn't contact the service and we can't continue working with any Nepomuk related code. This is so because the user can disable the Nepomuk service for his session.

Retrieve Metadata

Let's get the metadata for a file. Imagine the URL or the file is stored in uri.

Nepomuk::Resource res( uri ); QHash<QUrl, Variant> properties = res.properties();

That gives us all properties assigned to the file.

We can now use Nepomuk to get human readable labels for the properties and display the properties in a generic way:

for( QHash<QUrl, Variant>::const_iterator it = properties.constBegin();

    it != properties.constEnd(); ++it ) {
  QUrl propertyUri = it.key();
  Variant value = it.value();

  Nepomuk::Types::Class propertyType( propertyUri );

  someList->appendItem( propertyType.label() + ": " + value.toString() );

}

Set Metadata

Again uri is the URL of the file we want to set some metadata for. This time we want to set a tag and a comment and will do this in two slightly different ways:

Let's start with the tag and use the easy Nepomukish way:

Nepomuk::Tag tag( "This is my nice tag name" ); Nepomuk::Resource res( uri ); res.addTag( tag );

Simple! Actually if the tag already exists it will be reused.

Now let's set a comment for the file without the use of the convenience methods in Nepomuk:

Nepomuk::Resource res( uri ); QString comment = getFancyFileComment(); res.setProperty( Soprano::Vocabulary::NAO::description(), comment );

That's all. The comment is saved and will now be searchable via Nepomuk.