diff --git a/sql/Makefile b/sql/Makefile
index c6cab721..9b819237 100644
--- a/sql/Makefile
+++ b/sql/Makefile
@@ -1,49 +1,50 @@
 # Depends: postgresql-client, postgresql-autodoc
 
 DBNAME = softwareheritage-dev
 DOCDIR = autodoc
 
 SQL_INIT   = swh-init.sql
 SQL_SCHEMA = swh-schema.sql
 SQL_FUNC   = swh-func.sql
 SQL_DATA   = swh-data.sql
 SQLS = $(SQL_INIT) $(SQL_SCHEMA) $(SQL_FUNC) $(SQL_DATA)
 
 PSQL_BIN = psql
 PSQL_FLAGS = --single-transaction --echo-all
 PSQL = $(PSQL_BIN) $(PSQL_FLAGS)
 
 
 all:
 
 createdb: createdb-stamp
 createdb-stamp: $(SQL_INIT)
 	createdb $(DBNAME)
 	touch $@
 
 filldb: filldb-stamp
 filldb-stamp: createdb-stamp
 	cat $(SQLS) | $(PSQL) $(DBNAME)
 	touch $@
 
 dropdb:
 	dropdb $(DBNAME)
 
 dumpdb: swh.dump
 swh.dump: filldb-stamp
 	pg_dump -Fc $(DBNAME) > $@
 
 doc: doc-stamp
 doc-stamp: filldb-stamp
 	test -d $(DOCDIR)/ || mkdir $(DOCDIR)
 	postgresql_autodoc -d $(DBNAME) -f $(DOCDIR)/swh
+	bin/dot_add_content $(DOCDIR)/swh.dot clusters.dot
 	dot -T pdf $(DOCDIR)/swh.dot > $(DOCDIR)/swh.pdf
 	touch $@
 
 clean:
 	rm -rf *-stamp $(DOCDIR)/
 
 distclean: clean dropdb
 	rm -f swh.dump
 
 .PHONY: all initdb createdb dropdb doc clean
diff --git a/sql/bin/dot_add_content b/sql/bin/dot_add_content
new file mode 100755
index 00000000..679fdf31
--- /dev/null
+++ b/sql/bin/dot_add_content
@@ -0,0 +1,20 @@
+#!/bin/bash
+
+# Depends: moreutils
+
+DOT_FILE="$1"
+DOT_EXTRA="$2"
+if [ -z "$DOT_FILE" -o -z "$DOT_EXTRA" ] ; then
+    echo "Usage: $0 DOT_FILE DOT_EXTRA"
+    exit 1
+fi
+
+if ! [ -x $(which sponge) ] ; then
+    echo "Can't find sponge. Please: apt-get install moreutils"
+    exit 1
+fi
+
+(head -n -1 "$DOT_FILE" ;
+ cat "$DOT_EXTRA" ;
+ echo "}") \
+    | sponge "$DOT_FILE"
diff --git a/sql/clusters.dot b/sql/clusters.dot
new file mode 100644
index 00000000..92101753
--- /dev/null
+++ b/sql/clusters.dot
@@ -0,0 +1,58 @@
+subgraph cluster_meta {
+	label = "Meta";
+	dbversion;
+}
+
+subgraph cluster_content {
+	label = "Content";
+	content;
+}
+
+subgraph cluster_directory {
+	label = "Directories";
+	directory;
+	directory_entry_dir;
+	directory_entry_file;
+	directory_list_dir;
+	directory_list_file;
+}
+
+directory_entry_file -> content;
+
+subgraph cluster_revision {
+	label = "Revisions";
+	revision;
+	revision_history;
+	person;
+}
+
+revision -> directory;
+
+subgraph cluster_release {
+	label = "Releases";
+	release;
+}
+
+subgraph cluster_occurrences {
+	label = "Occurrences";
+	occurrence;
+	occurrence_history;
+}
+
+subgraph cluster_origins {
+	label = "Origins";
+	origin;
+	fetch_history;
+}
+
+subgraph cluster_projects {
+	label = "Projects";
+	project;
+	project_history;
+}
+
+subgraph cluster_organization {
+	label = "Organizations";
+	organization;
+	list_history;
+}