diff --git a/arelight/backend/d3js/relations_graph_builder.py b/arelight/backend/d3js/relations_graph_builder.py
index 47d87f9..3bc9a23 100644
--- a/arelight/backend/d3js/relations_graph_builder.py
+++ b/arelight/backend/d3js/relations_graph_builder.py
@@ -88,4 +88,4 @@ def __get_type(v):
     node_max = max(used_nodes.values()) if used_nodes else 0
     nodes = [{"id": id, "c": used_nodes[id]/node_max if weights else 1} for id in used_nodes]
 
-    return {"basis": graph_name, "nodes": nodes, "links": links}
+    return {"basis": [graph_name], "equation": "["+graph_name+"]", "nodes": nodes, "links": links}
diff --git a/arelight/backend/d3js/relations_graph_operations.py b/arelight/backend/d3js/relations_graph_operations.py
index a455779..88eacc1 100644
--- a/arelight/backend/d3js/relations_graph_operations.py
+++ b/arelight/backend/d3js/relations_graph_operations.py
@@ -93,8 +93,12 @@ def link_key(link):
         used_nodes[t] = used_nodes.get(t, 0) + c
 
     nodes = [{"id": id, "c": c} for id, c in used_nodes.items()]
-    basis = "(" + graph_A["basis"] + ")" + OPERATION_MAP[operation] + "(" + graph_B["basis"] + ")"
-    result_graph = {"basis": basis, "nodes": nodes, "links": links}
+    if operation == OP_DIFFERENCE:
+        basis = list(set(graph_A["basis"])-set(graph_B["basis"]))
+    else:
+        basis = list(set(graph_A["basis"])+set(graph_B["basis"]))
+    equation = "(" + graph_A["equation"] + ")" + OPERATION_MAP[operation] + "(" + graph_B["equation"] + ")"
+    result_graph = {"basis": basis, "equation": equation, "nodes": nodes, "links": links}
 
     # Assign weights if not used.
     if not weights: