diff --git a/sql/clusters.dot b/sql/clusters.dot
index 6ac88c7b..718abcbb 100644
--- a/sql/clusters.dot
+++ b/sql/clusters.dot
@@ -1,78 +1,87 @@
 
 subgraph "logical_grouping" {
 	style = rounded;
 	bgcolor = gray95;
 	color = gray;
 	
 	subgraph cluster_meta {
 		label = <<b>meta</b>>;
 		dbversion;
 	}
 
 	subgraph cluster_content {
 		label = <<b>content</b>>;
 		content;
 	}
 
 	subgraph cluster_directory {
 		label = <<b>directories</b>>;
 		directory;
 		directory_entry_dir;
 		directory_entry_file;
 		directory_entry_rev;
 		directory_list_dir;
 		directory_list_file;
 		directory_list_rev;
+
+		{rank=same;
+			directory_list_dir
+			directory_list_file
+			directory_list_rev}
+		{rank=same;
+			directory_entry_dir
+			directory_entry_file
+			directory_entry_rev}
 	}
 
 	subgraph cluster_revision {
 		label = <<b>revisions</b>>;
 		revision;
 		revision_history;
 		person;
 	}
 
 	subgraph cluster_release {
 		label = <<b>releases</b>>;
 		release;
 	}
 
 	subgraph cluster_occurrences {
 		label = <<b>occurrences</b>>;
 		occurrence;
 		occurrence_history;
 	}
 
 	subgraph cluster_origins {
 		label = <<b>origins</b>>;
 		origin;
 		fetch_history;
 	}
 
 	subgraph cluster_projects {
 		label = <<b>projects</b>>;
 		project;
 		project_history;
 	}
 
 	subgraph cluster_organization {
 		label = <<b>organizations</b>>;
 		organization;
 		list_history;
 	}
 
 	{
 		edge [style = dashed];
 
 		# "rtcolN" identifies the N-th row in a table, as a source
 		# "ltcolN" identifies the N-th row in a table, as a destination
 		"directory_entry_dir":rtcol2 -> "directory":ltcol1;
 		"directory_entry_file":rtcol2 -> "content":ltcol1;
 		"directory_entry_rev":rtcol2 -> "revision":ltcol1;
 		"directory_list_dir":rtcol2 -> "directory_entry_dir":ltcol1;
 		"directory_list_file":rtcol2 -> "directory_entry_file":ltcol1;
 		"directory_list_rev":rtcol2 -> "directory_entry_rev":ltcol1;
 		"revision":rtcol7 -> "directory":ltcol1;
 	}
 
 }