diff --git a/doc/schema.dot b/doc/schema.dot
new file mode 100644
index 0000000..2157596
--- /dev/null
+++ b/doc/schema.dot
@@ -0,0 +1,87 @@
+digraph "$schema" {
+	rankdir=RL
+	node [ shape=plaintext ]
+	archived_versions [ label=<
+		<table>
+			<tr><td colspan="5">archived_versions</td></tr>
+			<tr><td colspan="5"></td></tr>
+			<tr><td port="id_out"></td><td>id</td><td>INT(11)</td><td></td><td port="id_in"></td></tr>
+			<tr><td port="volume_out"></td><td>volume</td><td>INT(11)</td><td></td><td port="volume_in"></td></tr>
+			<tr><td port="version_out"></td><td>version</td><td>INT(11)</td><td></td><td port="version_in"></td></tr>
+			<tr><td port="file_out"></td><td>file</td><td>INT(11)</td><td></td><td port="file_in"></td></tr>
+			<tr><td port="offset_out"></td><td>offset</td><td>BIGINT(20)</td><td></td><td port="offset_in"></td></tr>
+		</table>>]
+        archived_versions:volume_out -> volumes:id_in
+        archived_versions:version_out -> versions2:id_in
+        archived_versions:file_out -> files:id_in
+	files [ label=<
+		<table>
+			<tr><td colspan="5">files</td></tr>
+			<tr><td colspan="5"></td></tr>
+			<tr><td port="id_out"></td><td>id</td><td>INT(11)</td><td></td><td port="id_in"></td></tr>
+			<tr><td port="path_out"></td><td>path</td><td>TEXT(65535)</td><td></td><td port="path_in"></td></tr>
+			<tr><td port="fileset_out"></td><td>fileset</td><td>INT(11)</td><td></td><td port="fileset_in"></td></tr>
+		</table>>]
+        files:fileset_out -> filesets:id_in
+	filesets [ label=<
+		<table>
+			<tr><td colspan="5">filesets</td></tr>
+			<tr><td colspan="5"></td></tr>
+			<tr><td port="id_out"></td><td>id</td><td>INT(11)</td><td></td><td port="id_in"></td></tr>
+			<tr><td port="host_out"></td><td>host</td><td>VARCHAR(255)</td><td></td><td port="host_in"></td></tr>
+			<tr><td port="dir_out"></td><td>dir</td><td>TEXT(65535)</td><td></td><td port="dir_in"></td></tr>
+			<tr><td port="options_out"></td><td>options</td><td>TEXT(65535)</td><td></td><td port="options_in"></td></tr>
+			<tr><td port="pid_out"></td><td>pid</td><td>INT(11)</td><td></td><td port="pid_in"></td></tr>
+			<tr><td port="active_out"></td><td>active</td><td>TINYINT(4)</td><td></td><td port="active_in"></td></tr>
+		</table>>]
+	instances [ label=<
+		<table>
+			<tr><td colspan="5">instances</td></tr>
+			<tr><td colspan="5"></td></tr>
+			<tr><td port="id_out"></td><td>id</td><td>BIGINT(20)</td><td></td><td port="id_in"></td></tr>
+			<tr><td port="file_out"></td><td>file</td><td>INT(11)</td><td></td><td port="file_in"></td></tr>
+			<tr><td port="file_id_out"></td><td>file_id</td><td>VARCHAR(255)</td><td></td><td port="file_id_in"></td></tr>
+			<tr><td port="date_out"></td><td>date</td><td>INT(11)</td><td></td><td port="date_in"></td></tr>
+			<tr><td port="online_out"></td><td>online</td><td>TINYINT(1)</td><td></td><td port="online_in"></td></tr>
+			<tr><td port="session_out"></td><td>session</td><td>INT(11)</td><td></td><td port="session_in"></td></tr>
+			<tr><td port="version_out"></td><td>version</td><td>INT(11)</td><td></td><td port="version_in"></td></tr>
+		</table>>]
+        instances:file_out -> files:id_in
+        instances:session_out -> sessions:id_in
+        instances:version_out -> versions2:id_in
+	sessions [ label=<
+		<table>
+			<tr><td colspan="5">sessions</td></tr>
+			<tr><td colspan="5"></td></tr>
+			<tr><td port="id_out"></td><td>id</td><td>INT(11)</td><td></td><td port="id_in"></td></tr>
+			<tr><td port="start_date_out"></td><td>start_date</td><td>INT(11)</td><td></td><td port="start_date_in"></td></tr>
+			<tr><td port="end_date_out"></td><td>end_date</td><td>INT(11)</td><td></td><td port="end_date_in"></td></tr>
+			<tr><td port="prefix_out"></td><td>prefix</td><td>VARCHAR(255)</td><td></td><td port="prefix_in"></td></tr>
+		</table>>]
+	versions2 [ label=<
+		<table>
+			<tr><td colspan="5">versions2</td></tr>
+			<tr><td colspan="5"></td></tr>
+			<tr><td port="id_out"></td><td>id</td><td>INT(11)</td><td></td><td port="id_in"></td></tr>
+			<tr><td port="file_type_out"></td><td>file_type</td><td>CHAR(1)</td><td></td><td port="file_type_in"></td></tr>
+			<tr><td port="file_size_out"></td><td>file_size</td><td>BIGINT(20)</td><td></td><td port="file_size_in"></td></tr>
+			<tr><td port="file_mtime_out"></td><td>file_mtime</td><td>INT(11)</td><td></td><td port="file_mtime_in"></td></tr>
+			<tr><td port="file_owner_out"></td><td>file_owner</td><td>VARCHAR(255)</td><td></td><td port="file_owner_in"></td></tr>
+			<tr><td port="file_group_out"></td><td>file_group</td><td>VARCHAR(255)</td><td></td><td port="file_group_in"></td></tr>
+			<tr><td port="file_acl_out"></td><td>file_acl</td><td>VARCHAR(255)</td><td></td><td port="file_acl_in"></td></tr>
+			<tr><td port="file_unix_bits_out"></td><td>file_unix_bits</td><td>SET(20)</td><td></td><td port="file_unix_bits_in"></td></tr>
+			<tr><td port="file_rdev_out"></td><td>file_rdev</td><td>INT(11)</td><td></td><td port="file_rdev_in"></td></tr>
+			<tr><td port="checksum_out"></td><td>checksum</td><td>VARCHAR(255)</td><td></td><td port="checksum_in"></td></tr>
+			<tr><td port="file_linktarget_out"></td><td>file_linktarget</td><td>TEXT(65535)</td><td></td><td port="file_linktarget_in"></td></tr>
+		</table>>]
+	volumes [ label=<
+		<table>
+			<tr><td colspan="5">volumes</td></tr>
+			<tr><td colspan="5"></td></tr>
+			<tr><td port="id_out"></td><td>id</td><td>INT(11)</td><td></td><td port="id_in"></td></tr>
+			<tr><td port="label_out"></td><td>label</td><td>VARCHAR(255)</td><td></td><td port="label_in"></td></tr>
+			<tr><td port="barcode_out"></td><td>barcode</td><td>VARCHAR(255)</td><td></td><td port="barcode_in"></td></tr>
+			<tr><td port="filesize_out"></td><td>filesize</td><td>BIGINT(20)</td><td></td><td port="filesize_in"></td></tr>
+			<tr><td port="blocksize_out"></td><td>blocksize</td><td>INT(11)</td><td></td><td port="blocksize_in"></td></tr>
+		</table>>]
+}
diff --git a/doc/schema.png b/doc/schema.png
new file mode 100644
index 0000000..f58a3ee
Binary files /dev/null and b/doc/schema.png differ