diff --git a/sql/clusters.dot b/sql/clusters.dot
index 9bda3bc7..2fb7eb7c 100644
--- a/sql/clusters.dot
+++ b/sql/clusters.dot
@@ -1,85 +1,85 @@
 
 subgraph "logical_grouping" {
 	style = rounded;
 	bgcolor = gray95;
 	color = gray;
 	
 	subgraph cluster_meta {
 		label = <<b>schema versioning</b><br /> version: @@VERSION@@>;
 		dbversion;
 	}
 
 	subgraph cluster_content {
 		label = <<b>content</b>>;
 		content;
 		skipped_content;
 	}
 
 	subgraph cluster_directory {
 		label = <<b>directories</b>>;
 		directory;
 		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_snapshots {
 		label = <<b>snapshots</b>>;
 		snapshot;
 		snapshot_branch;
 		snapshot_branches;
 	}
 
 	subgraph cluster_origins {
 		label = <<b>origins</b>>;
 		origin;
 		fetch_history;
 		origin_visit;
 	}
 
 	subgraph cluster_metadata {
                 label = <<b>metadata</b>>;
                 metadata_provider;
                 origin_metadata;
 		tool;
 	}
 
 	subgraph cluster_statistics {
                 label = <<b>statistics</b>>;
                 object_counts;
                 object_counts_bucketed;
 	}
 
 	{
 		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
+		# "rtcolN" identifies the N-th row (1-based) in a table, as a source
+		# "ltcolN" identifies the N-th row (1-based) in a table, as a destination
 		"snapshot_branch":rtcol3 -> "release":ltcol1;
 		"snapshot_branch":rtcol3 -> "revision":ltcol1;
 		"snapshot_branch":rtcol3 -> "directory":ltcol1;
 		"snapshot_branch":rtcol3 -> "content":ltcol2;
-		"directory_entry_dir":rtcol2 -> "directory":ltcol1;
+		"directory_entry_dir":ltcol2 -> "directory":rtcol1;
 		"directory_entry_file":rtcol2 -> "content":ltcol2;
 		"directory_entry_file":rtcol2 -> "skipped_content":ltcol2;
 		"directory_entry_rev":rtcol2 -> "revision":ltcol1;
 		"directory":rtcol2 -> "directory_entry_dir":ltcol1;
 		"directory":rtcol3 -> "directory_entry_file":ltcol1;
 		"directory":rtcol4 -> "directory_entry_rev":ltcol1;
 		"release":rtcol2 -> "revision":ltcol1;
-		"revision":rtcol7 -> "directory":ltcol1;
+		"revision":ltcol7 -> "directory":rtcol1;
 		"revision_history":rtcol2 -> "revision":ltcol1;
 	}
 }