I think this should be "little o" operation, or not mentioned as an operation to load the raster, but something like, _represents the raster with the given ID of RASTER_NAME. This does not load the raster right away, but instead describes loading that raster from the catalog in the future._ I've been meaning to document the difference, but little o operations are the general concept of an operation that you would run against rasters, like map algebra operations. Big O operations are the Op[T]'s that wrap work done through the Akka execution engine. Understanding Big O operations, and how they are separate from DataSource etc might be a bit much to lay on someone for this sort of tutorial. We might want to just link to the appropriate documentation, and not use the big-o version of Operation, to avoid confusion.