                              +----------------+
                              |     Index      |
                              | store passages |
                              +----------------+
                                       ^
+------------+                         |            +------------+
|   Draft    |------------------------------------->|    Gate    |
| cite keys  |                         |            | check keys |
+------------+                         |            +------------+
                   +-------------------+
                   |
            +------------+
            |   Parse    |
            | read PDFs  |
            +------------+
