--- a/schema/gemma.sql	Fri Feb 14 16:48:07 2020 +0100
+++ b/schema/gemma.sql	Fri Feb 14 17:31:17 2020 +0100
@@ -414,6 +414,20 @@
         CHECK (to_regclass(schema || '.' || name) IS NOT NULL
             OR view_def IS NOT NULL)
     )
+
+    CREATE TABLE layer_groups (
+       name varchar PRIMARY KEY
+    )
+
+    CREATE TABLE grouped_layers (
+       group_name varchar REFERENCES layer_groups ON DELETE CASCADE,
+       schema     varchar,
+       name       varchar,
+       ord        int NOT NULL DEFAULT 0,
+       PRIMARY KEY (group_name, schema, name),
+       UNIQUE (group_name, schema, name, ord),
+       FOREIGN KEY(schema, name) REFERENCES published_services
+    )
 ;