storage-engine-playground/crates/README.md

## Crates

Each subdirectory is a Cargo package with its own `Cargo.toml`.
Layout:

```text
crates/
  app-name/
    Cargo.toml
    src/
      main.rs
```

### Responsibilities and Dependencies

| Crate            | Kind            | Responsibility                                                                                                          | Depends On                                                 |
|------------------|-----------------|-------------------------------------------------------------------------------------------------------------------------|------------------------------------------------------------|
| `storage`        | library         | Backend-agnostic `Storage` and `Transaction` traits, plus adapters: `MemoryStorage`, `LmdbStorage`, `RedbStorage`, `FjallStorage`, `SqliteStorage`, `GeomergeStorage` (feature-gated). Owns `Value`, `Table`, `RowId`, `StorageError`, `CodecError`. | external `geomerge` (only with the `geomerge` feature)     |
| `query-ops`      | library         | Snapshot query operators: `scan_atom`, `semijoin`, `natural_join`. Owns `Relation`, `AtomPattern`, `Term`.                | `storage`                                                  |
| `plan-runner`    | library + `plan-run` CLI | Executes JSON plan IR against a chosen `Storage` backend via `--backend {memory \| memory-storage \| lmdb \| redb \| fjall \| sqlite \| geomerge}`. Walks the DAG using `query-ops` operators and verifies against `expected_bindings`. | `query-ops`, `storage` (all adapter features)              |
| `geomerge-demo`  | binary          | End-to-end example exercising `GeomergeStorage`: theory loading, transactional inserts, scan, persistence round trip, law validation. | `storage` (with `geomerge`), external `geomerge`           |

The dependency edges form a strict DAG:

```text
storage  ◄── query-ops  ◄── plan-runner
   ▲                              │
   └── geomerge-demo              │
       (also depends on            │
        external geomerge)         │
                                   ▼
                              (all storage features on)
```

No cycles, no upward dependencies.
`query-ops` and `plan-runner` are layered above `storage`;
`geomerge-demo` sits beside them as a runnable example.