Rekall is a database front-end. It is not itself a database -- data is stored somewhere else, in an SQL server, and Rekall is fundamentally just a tool to extract, display and update that data (of course, it does lots more than that, it does forms and reports and scripting and so on). It is database agnostic, and does not have any preferred database in the sense that Access® uses the Jet® database engine.
This is a tool to create, design and edit database files compatible with SQLite.
