Function derive_prefixes_system 

pub fn derive_prefixes_system<L: Component>(
    query: Query<'_, '_, (Entity, &Label, &Element), (Changed<Element>, With<L>)>,
    commands: Commands<'_, '_>,
)

Derive the Prefixes component (declared prefix → namespace map + base URL) from the parsed Element model. The language marker L is used only to scope the query (With<L>), so Turtle, TriG and any other language whose element is the shared Turtle model reuse one implementation.