Overview

Tracker SPARQL allows creating and connecting to one or more triplestore databases. It is used by the Tracker Miners filesystem indexer, and can also store and publish any kind of app data.

Querying data is done using the SPARQL graph query language. See the examples to find out how this works. Storing data can also be done using SPARQL, or using the TrackerResource API.

You can share a database over D-Bus using the TrackerEndpoint API, allowing other libtracker-sparql users to query from it, either by referencing it in a SELECT { SERVICE ... } query, or by connecting directly with tracker_sparql_connection_bus_new.

Tracker SPARQL partitions the database into multiple graphs. You can implementing access control restrictions based on graphs, and we provide a Flatpak portal that does so. The number of graphs is limited.

Connection methods

You can create and access a private store using tracker_sparql_connection_new. This is useful to store app-specific data.

To connect to another database on the same local machine, such as the one exposed by Tracker Miner FS, use tracker_sparql_connection_bus_new.

To connect to another a database on a remote machine, use tracker_sparql_connection_remote_new. This can be used to query online databases that provide a SPARQL endpoint, such as DBpedia. .

Connecting from Flatpak

Tracker SPARQL provides a portal for the Flatpak application sandboxing system. This lets you control which parts of a database each app can query.

The app's Flatpak manifest needs to specify which graph(s) the app will access. See the example app and the portal documentation to see how.

No code changes are needed in the app, as tracker_sparql_connection_bus_new will automatically try connect via the portal if it can't talk to the given D-Bus name directly.

Tracker SPARQL is included in the GNOME Flatpak SDK and runtime. If the app uses a different runtime, you may need to build Tracker SPARQL in the app manifest.

The app might use the Tracker Miner FS search index. Ideally this is done via the portal, using the search index maintained on the host. Since not all OSes ship tracker-miner-fs-3, we recommend that apps bundle it inside the Flatpak and connect to the bundled version as a fallback. See GNOME Music for an example of how to do this.

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