Projects/Nepomuk/BulkChanges

Making Bulk Changes

Quite often one needs to apply some changes to a large number of resources. Instead of using the Resource class which is synchronous. They are easier ways, which are asynchronous.

With KDE 4.9 the Nepomuk Datamanagement libraries finally became public and allow clients to make large bulk changes to Nepomuk. In fact they are now the de facto method of modifying data. All other client libraries are now built on top of the Data Management library.

Includes and Libraries

Since the datamanagement libraries are so prevalent, they come bundled together with the NepomukCore library.

The appropriate functions are included in the Nepomuk/DataManagement include file.

Jobs

Each Datamanagement function returns a KJob which performs the jobs and returns a signal on completion. These jobs are automatically started, and like all other KJobs they are automatically deleted on completion.

Errors

While these jobs are quite easy to use, they have inbuilt error checking that verifies the domain, range and cardinality of the properties that are being changed. Therefore it is important to check the error code of the job when it returns. A better error message can be received via KJob::errorString

Examples

Setting the tags for a large number of resources -

    QList<QUrl> resourceList;
    QVariantList tagResources;

    KJob* job = setProperty( resourceList, NAO::hasTag(), tagResources );
    connect( job, SIGNAL(result(KJob*)), this, SLOT(slotTagUpdateDone()) );

This can also be done synchronously by running an event loop in the background -

    KJob* job = setProperty( resourceList, NAO::hasTag(), tagResources );
    job->exec();
    if( job->error() )
        kError() << job->errorString();