diff --git a/api/change_set.py b/api/change_set.py
index 64c9798..7e91608 100644
--- a/api/change_set.py
+++ b/api/change_set.py
@@ -1,14 +1,12 @@
 class ChangeSet:
     def __init__(self) -> None:
-        self.added : list[dict[str, str]] = []
-        self.deleted : list[dict[str, str]] = []
-        self.updated : list[dict[str, str]] = []
+        self.operations : list[dict[str, str]] = []
 
     def add(self, type: str, id: str) -> None:
-        self.added.append({ 'type': type, 'id': id })
+        self.operations.append({ 'operation': 'add', 'type': type, 'id': id })
 
     def delete(self, type: str, id: str) -> None:
-        self.deleted.append({ 'type': type, 'id': id })
+        self.operations.append({ 'operation': 'delete', 'type': type, 'id': id })
 
-    def update(self, type: str, id: str, property_name: str, property_type: str, property_value: str) -> None:
-        self.updated.append({ 'type': type, 'id': id, 'property': property_name, 'property_type': property_type,  'property_value': property_value })
\ No newline at end of file
+    def update(self, type: str, id: str, property: str) -> None:
+        self.operations.append({ 'operation': 'update', 'type': type, 'id': id, 'property': property })
\ No newline at end of file
diff --git a/api/s1_title.py b/api/s1_title.py
index 4e34511..3d0e3a3 100644
--- a/api/s1_title.py
+++ b/api/s1_title.py
@@ -20,5 +20,5 @@ def set_title(name: str, value: str) -> ChangeSet:
         add_operation(name, redo, undo)
 
     change = ChangeSet()
-    change.update('title', 'null', 'value', 'str', value)
+    change.update('title', 'null', 'value')
     return change
diff --git a/api/s24_coordinates.py b/api/s24_coordinates.py
index 2337f09..ddb8df1 100644
--- a/api/s24_coordinates.py
+++ b/api/s24_coordinates.py
@@ -39,5 +39,5 @@ def set_node_coord(name: str, node_type: str, id: str, x: float, y: float) -> Ch
         add_operation(name, redo, undo)
 
     change = ChangeSet()
-    change.update(node_type, id, 'coord', 'point', str({'x': x, 'y': y}))
+    change.update(node_type, id, 'coord')
     return change
diff --git a/api/utility.py b/api/utility.py
index f7e417a..da09b0e 100644
--- a/api/utility.py
+++ b/api/utility.py
@@ -30,5 +30,5 @@ def update(name: str, type: str, table: str, id_key: str, id_value: str, key: st
         add_operation(name, redo, undo)
 
     change = ChangeSet()
-    change.update(type, id_value, key, key_type, value)
+    change.update(type, id_value, key)
     return change
diff --git a/test_tjnetwork.py b/test_tjnetwork.py
index 7ef7a28..85e1de7 100644
--- a/test_tjnetwork.py
+++ b/test_tjnetwork.py
@@ -35,9 +35,10 @@ class TestApi:
         self.enter(p)
 
         change_set = add_junction(p, "j0", 0.0, 10.0, 20.0)
-        assert len(change_set.added) == 1
-        assert change_set.added[0]['type'] == JUNCTION
-        assert change_set.added[0]['id'] == "j0"
+        assert len(change_set.operations) == 1
+        assert change_set.operations[0]['operation'] == 'add'
+        assert change_set.operations[0]['type'] == JUNCTION
+        assert change_set.operations[0]['id'] == "j0"
         coord = get_junction_coord(p, 'j0')
         assert coord['x'] == 0.0
         assert coord['y'] == 10.0
@@ -47,23 +48,23 @@ class TestApi:
         assert get_junction_demand(p, 'j') == None
         assert get_junction_demand(p, 'j0') == "NULL"
         change_set = set_junction_demand(p, 'j0', 100.0)
-        assert len(change_set.updated) == 1
-        assert change_set.updated[0]['type'] == JUNCTION
-        assert change_set.updated[0]['id'] == 'j0'
-        assert change_set.updated[0]['property'] == 'demand'
-        assert change_set.updated[0]['property_type'] == 'float'
-        assert change_set.updated[0]['property_value'] == str(100.0)
+        assert len(change_set.operations) == 1
+        assert change_set.operations[0]['operation'] == 'update'
+        assert change_set.operations[0]['type'] == JUNCTION
+        assert change_set.operations[0]['id'] == 'j0'
+        assert change_set.operations[0]['property'] == 'demand'
         assert get_junction_demand(p, 'j0') == 100.0
 
         # TODO: pattern
 
         change_set = add_junction(p, "j1", 0.0, 10.0, 20.0)
-        assert len(change_set.added) == 1
-        assert change_set.added[0]['type'] == JUNCTION
-        assert change_set.added[0]['id'] == "j1"
+        assert len(change_set.operations) == 1
+        assert change_set.operations[0]['operation'] == 'add'
+        assert change_set.operations[0]['type'] == JUNCTION
+        assert change_set.operations[0]['id'] == "j1"
 
         change_set = add_junction(p, "j1", 0.0, 10.0, 20.0)
-        assert len(change_set.added) == 0
+        assert len(change_set.operations) == 0
 
         nodes = get_nodes(p)
         assert len(nodes) == 2
@@ -71,21 +72,23 @@ class TestApi:
         assert nodes[1] == "j1"
 
         change_set = delete_junction(p, 'j1')
-        assert len(change_set.deleted) == 1
-        assert change_set.deleted[0]['type'] == JUNCTION
-        assert change_set.deleted[0]['id'] == "j1"
+        assert len(change_set.operations) == 1
+        assert change_set.operations[0]['operation'] == 'delete'
+        assert change_set.operations[0]['type'] == JUNCTION
+        assert change_set.operations[0]['id'] == "j1"
 
         change_set = delete_junction(p, 'j1')
-        assert len(change_set.deleted) == 0
+        assert len(change_set.operations) == 0
 
         nodes = get_nodes(p)
         assert len(nodes) == 1
         assert nodes[0] == "j0"
 
         change_set = delete_junction(p, 'j0')
-        assert len(change_set.deleted) == 1
-        assert change_set.deleted[0]['type'] == JUNCTION
-        assert change_set.deleted[0]['id'] == "j0"
+        assert len(change_set.operations) == 1
+        assert change_set.operations[0]['operation'] == 'delete'
+        assert change_set.operations[0]['type'] == JUNCTION
+        assert change_set.operations[0]['id'] == "j0"
 
         nodes = get_nodes(p)
         assert len(nodes) == 0
@@ -97,40 +100,38 @@ class TestApi:
         self.enter(p)
 
         change_set = add_reservoir(p, "r0", 0.0, 10.0, 20.0)
-        assert len(change_set.added) == 1
-        assert change_set.added[0]['type'] == RESERVOIR
-        assert change_set.added[0]['id'] == "r0"
+        assert len(change_set.operations) == 1
+        assert change_set.operations[0]['operation'] == 'add'
+        assert change_set.operations[0]['type'] == RESERVOIR
+        assert change_set.operations[0]['id'] == "r0"
 
         change_set = add_reservoir(p, "r0", 0.0, 10.0, 20.0)
-        assert len(change_set.added) == 0
+        assert len(change_set.operations) == 0
 
         assert get_reservoir_head(p, 'r0') == 20.0
         change_set = set_reservoir_head(p, 'r0', 100.0)
-        assert change_set.updated[0]['type'] == RESERVOIR
-        assert change_set.updated[0]['id'] == 'r0'
-        assert change_set.updated[0]['property'] == 'head'
-        assert change_set.updated[0]['property_type'] == 'float'
-        assert change_set.updated[0]['property_value'] == str(100.0)
+        assert change_set.operations[0]['type'] == RESERVOIR
+        assert change_set.operations[0]['id'] == 'r0'
+        assert change_set.operations[0]['property'] == 'head'
         assert get_reservoir_head(p, 'r0') == 100.0
 
         assert get_reservoir_coord(p, 'r0') == { 'x': 0.0, 'y': 10.0 }
         change_set = set_reservoir_coord(p, 'r0', 100.0, 200.0)
-        assert change_set.updated[0]['type'] == RESERVOIR
-        assert change_set.updated[0]['id'] == 'r0'
-        assert change_set.updated[0]['property'] == 'coord'
-        assert change_set.updated[0]['property_type'] == 'point'
-        assert change_set.updated[0]['property_value'] == str({'x': 100.0, 'y': 200.0})
+        assert change_set.operations[0]['type'] == RESERVOIR
+        assert change_set.operations[0]['id'] == 'r0'
+        assert change_set.operations[0]['property'] == 'coord'
         assert get_reservoir_coord(p, 'r0') == { 'x': 100.0, 'y': 200.0 }
 
         # TODO: pattern
 
         change_set = delete_reservoir(p, 'r0')
-        assert len(change_set.deleted) == 1
-        assert change_set.deleted[0]['type'] == RESERVOIR
-        assert change_set.deleted[0]['id'] == "r0"
+        assert len(change_set.operations) == 1
+        assert change_set.operations[0]['operation'] == 'delete'
+        assert change_set.operations[0]['type'] == RESERVOIR
+        assert change_set.operations[0]['id'] == "r0"
 
         change_set = delete_reservoir(p, 'r0')
-        assert len(change_set.deleted) == 0
+        assert len(change_set.operations) == 0
 
         self.leave(p)
 
@@ -140,17 +141,19 @@ class TestApi:
         self.enter(p)
 
         change_set = add_tank(p, "t0", 10.0, 10.0, 10.0, 10.0, 10.0, 10.0, 10.0, 10.0)
-        assert len(change_set.added) == 1
-        assert change_set.added[0]['type'] == TANK
-        assert change_set.added[0]['id'] == "t0"
+        assert len(change_set.operations) == 1
+        assert change_set.operations[0]['operation'] == 'add'
+        assert change_set.operations[0]['type'] == TANK
+        assert change_set.operations[0]['id'] == "t0"
 
         change_set = add_tank(p, "t1", 0.0, 10.0, 20.0)
-        assert len(change_set.added) == 1
-        assert change_set.added[0]['type'] == TANK
-        assert change_set.added[0]['id'] == "t1"
+        assert len(change_set.operations) == 1
+        assert change_set.operations[0]['operation'] == 'add'
+        assert change_set.operations[0]['type'] == TANK
+        assert change_set.operations[0]['id'] == "t1"
 
         change_set = add_tank(p, "t1", 0.0, 10.0, 20.0)
-        assert len(change_set.added) == 0
+        assert len(change_set.operations) == 0
 
         tanks = get_nodes(p)
         assert len(tanks) == 2
@@ -159,50 +162,56 @@ class TestApi:
 
         assert get_tank_elevation(p, 't0') == 10.0
         change_set = set_tank_elevation(p, 't0', 100.0)
-        assert len(change_set.updated) == 1
-        assert change_set.updated[0]['type'] == TANK
-        assert change_set.updated[0]['id'] == "t0"
-        assert change_set.updated[0]['property'] == 'elevation'
+        assert len(change_set.operations) == 1
+        assert change_set.operations[0]['operation'] == 'update'
+        assert change_set.operations[0]['type'] == TANK
+        assert change_set.operations[0]['id'] == "t0"
+        assert change_set.operations[0]['property'] == 'elevation'
         assert get_tank_elevation(p, 't0') == 100.0
 
         assert get_tank_init_level(p, 't0') == 10.0
         change_set = set_tank_init_level(p, 't0', 100.0)
-        assert len(change_set.updated) == 1
-        assert change_set.updated[0]['type'] == TANK
-        assert change_set.updated[0]['id'] == "t0"
-        assert change_set.updated[0]['property'] == 'init_level'
+        assert len(change_set.operations) == 1
+        assert change_set.operations[0]['operation'] == 'update'
+        assert change_set.operations[0]['type'] == TANK
+        assert change_set.operations[0]['id'] == "t0"
+        assert change_set.operations[0]['property'] == 'init_level'
         assert get_tank_init_level(p, 't0') == 100.0
 
         assert get_tank_min_level(p, 't0') == 10.0
         change_set = set_tank_min_level(p, 't0', 100.0)
-        assert len(change_set.updated) == 1
-        assert change_set.updated[0]['type'] == TANK
-        assert change_set.updated[0]['id'] == "t0"
-        assert change_set.updated[0]['property'] == 'min_level'
+        assert len(change_set.operations) == 1
+        assert change_set.operations[0]['operation'] == 'update'
+        assert change_set.operations[0]['type'] == TANK
+        assert change_set.operations[0]['id'] == "t0"
+        assert change_set.operations[0]['property'] == 'min_level'
         assert get_tank_min_level(p, 't0') == 100.0
 
         assert get_tank_max_level(p, 't0') == 10.0
         change_set = set_tank_max_level(p, 't0', 100.0)
-        assert len(change_set.updated) == 1
-        assert change_set.updated[0]['type'] == TANK
-        assert change_set.updated[0]['id'] == "t0"
-        assert change_set.updated[0]['property'] == 'max_level'
+        assert len(change_set.operations) == 1
+        assert change_set.operations[0]['operation'] == 'update'
+        assert change_set.operations[0]['type'] == TANK
+        assert change_set.operations[0]['id'] == "t0"
+        assert change_set.operations[0]['property'] == 'max_level'
         assert get_tank_max_level(p, 't0') == 100.0
 
         assert get_tank_diameter(p, 't0') == 10.0
         change_set = set_tank_diameter(p, 't0', 100.0)
-        assert len(change_set.updated) == 1
-        assert change_set.updated[0]['type'] == TANK
-        assert change_set.updated[0]['id'] == "t0"
-        assert change_set.updated[0]['property'] == 'diameter'
+        assert len(change_set.operations) == 1
+        assert change_set.operations[0]['operation'] == 'update'
+        assert change_set.operations[0]['type'] == TANK
+        assert change_set.operations[0]['id'] == "t0"
+        assert change_set.operations[0]['property'] == 'diameter'
         assert get_tank_diameter(p, 't0') == 100.0
 
         assert get_tank_min_vol(p, 't0') == 10.0
         change_set = set_tank_min_vol(p, 't0', 100.0)
-        assert len(change_set.updated) == 1
-        assert change_set.updated[0]['type'] == TANK
-        assert change_set.updated[0]['id'] == "t0"
-        assert change_set.updated[0]['property'] == 'min_vol'
+        assert len(change_set.operations) == 1
+        assert change_set.operations[0]['operation'] == 'update'
+        assert change_set.operations[0]['type'] == TANK
+        assert change_set.operations[0]['id'] == "t0"
+        assert change_set.operations[0]['property'] == 'min_vol'
         assert get_tank_min_vol(p, 't0') == 100.0
 
         # TODO: vol_curve
@@ -210,29 +219,32 @@ class TestApi:
         assert get_tank_overflow(p, 't') == None
         assert get_tank_overflow(p, 't0') == 'NULL'
         change_set = set_tank_overflow(p, 't0', "XXX")
-        assert len(change_set.updated) == 0
+        assert len(change_set.operations) == 0
         change_set = set_tank_overflow(p, 't0', OVERFLOW_YES)
-        assert len(change_set.updated) == 1
-        assert change_set.updated[0]['type'] == TANK
-        assert change_set.updated[0]['id'] == "t0"
-        assert change_set.updated[0]['property'] == 'overflow'
+        assert len(change_set.operations) == 1
+        assert change_set.operations[0]['operation'] == 'update'
+        assert change_set.operations[0]['type'] == TANK
+        assert change_set.operations[0]['id'] == "t0"
+        assert change_set.operations[0]['property'] == 'overflow'
         assert get_tank_overflow(p, 't0') == OVERFLOW_YES
 
         change_set = delete_tank(p, "t0")
-        assert len(change_set.deleted) == 1
-        assert change_set.deleted[0]['type'] == TANK
-        assert change_set.deleted[0]['id'] == "t0"
+        assert len(change_set.operations) == 1
+        assert change_set.operations[0]['operation'] == 'delete'
+        assert change_set.operations[0]['type'] == TANK
+        assert change_set.operations[0]['id'] == "t0"
 
         tanks = get_nodes(p)
         assert len(tanks) == 1
 
         change_set = delete_tank(p, "t1")
-        assert len(change_set.deleted) == 1
-        assert change_set.deleted[0]['type'] == TANK
-        assert change_set.deleted[0]['id'] == "t1"
+        assert len(change_set.operations) == 1
+        assert change_set.operations[0]['operation'] == 'delete'
+        assert change_set.operations[0]['type'] == TANK
+        assert change_set.operations[0]['id'] == "t1"
 
         change_set = delete_tank(p, "t1")
-        assert len(change_set.deleted) == 0
+        assert len(change_set.operations) == 0
 
         tanks = get_nodes(p)
         assert len(tanks) == 0
@@ -244,7 +256,7 @@ class TestApi:
         self.enter(p)
 
         change_set = add_pipe(p, 'p1', 'j1', 'j2', 10.0, 10.0, 10.0, 10.0, PIPE_STATUS_CLOSED)
-        assert len(change_set.added) == 0
+        assert len(change_set.operations) == 0
 
         add_junction(p, 'j1', 0.0, 0.0, 0.0)
         add_junction(p, 'j2', 10.0, 10.0, 0.0)
@@ -258,18 +270,19 @@ class TestApi:
         assert not is_link(p, 'p1')
 
         change_set = add_pipe(p, 'p1', 'j1', 'j2', 10.0, 10.0, 10.0, 10.0, "XXX")
-        assert len(change_set.added) == 0
+        assert len(change_set.operations) == 0
 
         change_set = add_pipe(p, 'p1', 'j1', 'j1', 10.0, 10.0, 10.0, 10.0, PIPE_STATUS_CLOSED)
-        assert len(change_set.added) == 0
+        assert len(change_set.operations) == 0
 
         change_set = add_pipe(p, 'p1', 'j1', 'j2', 10.0, 10.0, 10.0, 10.0, PIPE_STATUS_CLOSED)
-        assert len(change_set.added) == 1
-        assert change_set.added[0]['type'] == PIPE
-        assert change_set.added[0]['id'] == "p1"
+        assert len(change_set.operations) == 1
+        assert change_set.operations[0]['operation'] == 'add'
+        assert change_set.operations[0]['type'] == PIPE
+        assert change_set.operations[0]['id'] == "p1"
 
         change_set = add_pipe(p, 'p1', 'j1', 'j2', 10.0, 10.0, 10.0, 10.0, PIPE_STATUS_CLOSED)
-        assert len(change_set.added) == 0
+        assert len(change_set.operations) == 0
 
         pipes = get_links(p)
         assert len(pipes) == 1
@@ -283,53 +296,60 @@ class TestApi:
         assert get_pipe_status(p, 'p1') == PIPE_STATUS_CLOSED
 
         change_set = set_pipe_node1(p, 'p1', 'j2')
-        assert len(change_set.updated) == 0
+        assert len(change_set.operations) == 0
         change_set = set_pipe_node2(p, 'p1', 'j1')
-        assert len(change_set.updated) == 0
+        assert len(change_set.operations) == 0
         change_set = set_pipe_status(p, 'p1', "XXX")
-        assert len(change_set.updated) == 0
+        assert len(change_set.operations) == 0
 
         change_set = set_pipe_node1(p, 'p1', 'j3')
-        assert len(change_set.updated) == 1
-        assert change_set.updated[0]['type'] == PIPE
-        assert change_set.updated[0]['id'] == 'p1'
-        assert change_set.updated[0]['property'] == 'node1'
+        assert len(change_set.operations) == 1
+        assert change_set.operations[0]['operation'] == 'update'
+        assert change_set.operations[0]['type'] == PIPE
+        assert change_set.operations[0]['id'] == 'p1'
+        assert change_set.operations[0]['property'] == 'node1'
 
         change_set = set_pipe_node2(p, 'p1', 'j4')
-        assert len(change_set.updated) == 1
-        assert change_set.updated[0]['type'] == PIPE
-        assert change_set.updated[0]['id'] == 'p1'
-        assert change_set.updated[0]['property'] == 'node2'
+        assert len(change_set.operations) == 1
+        assert change_set.operations[0]['operation'] == 'update'
+        assert change_set.operations[0]['type'] == PIPE
+        assert change_set.operations[0]['id'] == 'p1'
+        assert change_set.operations[0]['property'] == 'node2'
 
         change_set = set_pipe_length(p, 'p1', 100.0)
-        assert len(change_set.updated) == 1
-        assert change_set.updated[0]['type'] == PIPE
-        assert change_set.updated[0]['id'] == 'p1'
-        assert change_set.updated[0]['property'] == 'length'
+        assert len(change_set.operations) == 1
+        assert change_set.operations[0]['operation'] == 'update'
+        assert change_set.operations[0]['type'] == PIPE
+        assert change_set.operations[0]['id'] == 'p1'
+        assert change_set.operations[0]['property'] == 'length'
 
         change_set = set_pipe_diameter(p, 'p1', 100.0)
-        assert len(change_set.updated) == 1
-        assert change_set.updated[0]['type'] == PIPE
-        assert change_set.updated[0]['id'] == 'p1'
-        assert change_set.updated[0]['property'] == 'diameter'
+        assert len(change_set.operations) == 1
+        assert change_set.operations[0]['operation'] == 'update'
+        assert change_set.operations[0]['type'] == PIPE
+        assert change_set.operations[0]['id'] == 'p1'
+        assert change_set.operations[0]['property'] == 'diameter'
 
         change_set = set_pipe_roughness(p, 'p1', 100.0)
-        assert len(change_set.updated) == 1
-        assert change_set.updated[0]['type'] == PIPE
-        assert change_set.updated[0]['id'] == 'p1'
-        assert change_set.updated[0]['property'] == 'roughness'
+        assert len(change_set.operations) == 1
+        assert change_set.operations[0]['operation'] == 'update'
+        assert change_set.operations[0]['type'] == PIPE
+        assert change_set.operations[0]['id'] == 'p1'
+        assert change_set.operations[0]['property'] == 'roughness'
 
         change_set = set_pipe_minor_loss(p, 'p1', 100.0)
-        assert len(change_set.updated) == 1
-        assert change_set.updated[0]['type'] == PIPE
-        assert change_set.updated[0]['id'] == 'p1'
-        assert change_set.updated[0]['property'] == 'minor_loss'
+        assert len(change_set.operations) == 1
+        assert change_set.operations[0]['operation'] == 'update'
+        assert change_set.operations[0]['type'] == PIPE
+        assert change_set.operations[0]['id'] == 'p1'
+        assert change_set.operations[0]['property'] == 'minor_loss'
 
         change_set = set_pipe_status(p, 'p1', PIPE_STATUS_OPEN)
-        assert len(change_set.updated) == 1
-        assert change_set.updated[0]['type'] == PIPE
-        assert change_set.updated[0]['id'] == 'p1'
-        assert change_set.updated[0]['property'] == 'status'
+        assert len(change_set.operations) == 1
+        assert change_set.operations[0]['operation'] == 'update'
+        assert change_set.operations[0]['type'] == PIPE
+        assert change_set.operations[0]['id'] == 'p1'
+        assert change_set.operations[0]['property'] == 'status'
 
         assert get_pipe_node1(p, 'p1') == 'j3'
         assert get_pipe_node2(p, 'p1') == 'j4'
@@ -340,30 +360,33 @@ class TestApi:
         assert get_pipe_status(p, 'p1') == PIPE_STATUS_OPEN
 
         change_set = add_pipe(p, 'p2', 'j1', 'j2', 10.0, 10.0, 10.0, 10.0, PIPE_STATUS_CLOSED)
-        assert len(change_set.added) == 1
-        assert change_set.added[0]['type'] == PIPE
-        assert change_set.added[0]['id'] == "p2"
+        assert len(change_set.operations) == 1
+        assert change_set.operations[0]['operation'] == 'add'
+        assert change_set.operations[0]['type'] == PIPE
+        assert change_set.operations[0]['id'] == "p2"
 
         pipes = get_links(p)
         assert len(pipes) == 2
 
         change_set = delete_pipe(p, 'p')
-        assert len(change_set.deleted) == 0
+        assert len(change_set.operations) == 0
 
         assert is_pipe(p, 'p1')
 
         change_set = delete_pipe(p, 'p1')
-        assert len(change_set.deleted) == 1
-        assert change_set.deleted[0]['type'] == PIPE
-        assert change_set.deleted[0]['id'] == "p1"
+        assert len(change_set.operations) == 1
+        assert change_set.operations[0]['operation'] == 'delete'
+        assert change_set.operations[0]['type'] == PIPE
+        assert change_set.operations[0]['id'] == "p1"
 
         pipes = get_links(p)
         assert len(pipes) == 1
 
         change_set = delete_pipe(p, 'p2')
-        assert len(change_set.deleted) == 1
-        assert change_set.deleted[0]['type'] == PIPE
-        assert change_set.deleted[0]['id'] == "p2"
+        assert len(change_set.operations) == 1
+        assert change_set.operations[0]['operation'] == 'delete'
+        assert change_set.operations[0]['type'] == PIPE
+        assert change_set.operations[0]['id'] == "p2"
 
         self.leave(p)
 
@@ -372,7 +395,7 @@ class TestApi:
         self.enter(p)
 
         change_set = add_pump(p, 'p1', 'j1', 'j2')
-        assert len(change_set.added) == 0
+        assert len(change_set.operations) == 0
 
         add_junction(p, 'j1', 0.0, 0.0, 0.0)
         add_junction(p, 'j2', 10.0, 10.0, 0.0)
@@ -386,15 +409,16 @@ class TestApi:
         assert not is_link(p, 'p1')
 
         change_set = add_pump(p, 'p1', 'j1', 'j1')
-        assert len(change_set.added) == 0
+        assert len(change_set.operations) == 0
 
         change_set = add_pump(p, 'p1', 'j1', 'j2')
-        assert len(change_set.added) == 1
-        assert change_set.added[0]['type'] == PUMP
-        assert change_set.added[0]['id'] == "p1"
+        assert len(change_set.operations) == 1
+        assert change_set.operations[0]['operation'] == 'add'
+        assert change_set.operations[0]['type'] == PUMP
+        assert change_set.operations[0]['id'] == "p1"
 
         change_set = add_pump(p, 'p1', 'j1', 'j2')
-        assert len(change_set.added) == 0
+        assert len(change_set.operations) == 0
 
         pumps = get_links(p)
         assert len(pumps) == 1
@@ -403,50 +427,55 @@ class TestApi:
         assert get_pump_node2(p, 'p1') == 'j2'
 
         change_set = set_pump_node1(p, 'p1', 'j2')
-        assert len(change_set.updated) == 0
+        assert len(change_set.operations) == 0
         change_set = set_pump_node2(p, 'p1', 'j1')
-        assert len(change_set.updated) == 0
+        assert len(change_set.operations) == 0
 
         change_set = set_pump_node1(p, 'p1', 'j3')
-        assert len(change_set.updated) == 1
-        assert change_set.updated[0]['type'] == PUMP
-        assert change_set.updated[0]['id'] == 'p1'
-        assert change_set.updated[0]['property'] == 'node1'
+        assert len(change_set.operations) == 1
+        assert change_set.operations[0]['operation'] == 'update'
+        assert change_set.operations[0]['type'] == PUMP
+        assert change_set.operations[0]['id'] == 'p1'
+        assert change_set.operations[0]['property'] == 'node1'
 
         change_set = set_pump_node2(p, 'p1', 'j4')
-        assert len(change_set.updated) == 1
-        assert change_set.updated[0]['type'] == PUMP
-        assert change_set.updated[0]['id'] == 'p1'
-        assert change_set.updated[0]['property'] == 'node2'
+        assert len(change_set.operations) == 1
+        assert change_set.operations[0]['operation'] == 'update'
+        assert change_set.operations[0]['type'] == PUMP
+        assert change_set.operations[0]['id'] == 'p1'
+        assert change_set.operations[0]['property'] == 'node2'
 
         assert get_pump_node1(p, 'p1') == 'j3'
         assert get_pump_node2(p, 'p1') == 'j4'
 
         change_set = add_pump(p, 'p2', 'j1', 'j2')
-        assert len(change_set.added) == 1
-        assert change_set.added[0]['type'] == PUMP
-        assert change_set.added[0]['id'] == "p2"
+        assert len(change_set.operations) == 1
+        assert change_set.operations[0]['operation'] == 'add'
+        assert change_set.operations[0]['type'] == PUMP
+        assert change_set.operations[0]['id'] == "p2"
 
         pumps = get_links(p)
         assert len(pumps) == 2
 
         change_set = delete_pump(p, 'p')
-        assert len(change_set.deleted) == 0
+        assert len(change_set.operations) == 0
 
         assert is_pump(p, 'p1')
 
         change_set = delete_pump(p, 'p1')
-        assert len(change_set.deleted) == 1
-        assert change_set.deleted[0]['type'] == PUMP
-        assert change_set.deleted[0]['id'] == "p1"
+        assert len(change_set.operations) == 1
+        assert change_set.operations[0]['operation'] == 'delete'
+        assert change_set.operations[0]['type'] == PUMP
+        assert change_set.operations[0]['id'] == "p1"
 
         pumps = get_links(p)
         assert len(pumps) == 1
 
         change_set = delete_pump(p, 'p2')
-        assert len(change_set.deleted) == 1
-        assert change_set.deleted[0]['type'] == PUMP
-        assert change_set.deleted[0]['id'] == "p2"
+        assert len(change_set.operations) == 1
+        assert change_set.operations[0]['operation'] == 'delete'
+        assert change_set.operations[0]['type'] == PUMP
+        assert change_set.operations[0]['id'] == "p2"
 
         self.leave(p)
 
@@ -455,7 +484,7 @@ class TestApi:
         self.enter(p)
 
         change_set = add_valve(p, 'v1', 'j1', 'j2', 10.0, VALVES_TYPE_FCV, 10.0, 10.0)
-        assert len(change_set.added) == 0
+        assert len(change_set.operations) == 0
 
         add_junction(p, 'j1', 0.0, 0.0, 0.0)
         add_junction(p, 'j2', 10.0, 10.0, 0.0)
@@ -469,18 +498,19 @@ class TestApi:
         assert not is_link(p, 'v1')
 
         change_set = add_valve(p, 'v1', 'j1', 'j2', 10.0, "xxx", 10.0, 10.0)
-        assert len(change_set.added) == 0
+        assert len(change_set.operations) == 0
 
         change_set = add_valve(p, 'v1', 'j1', 'j1', 10.0, VALVES_TYPE_FCV, 10.0, 10.0)
-        assert len(change_set.added) == 0
+        assert len(change_set.operations) == 0
 
         change_set = add_valve(p, 'v1', 'j1', 'j2', 10.0, VALVES_TYPE_FCV, 10.0, 10.0)
-        assert len(change_set.added) == 1
-        assert change_set.added[0]['type'] == VALVE
-        assert change_set.added[0]['id'] == "v1"
+        assert len(change_set.operations) == 1
+        assert change_set.operations[0]['operation'] == 'add'
+        assert change_set.operations[0]['type'] == VALVE
+        assert change_set.operations[0]['id'] == "v1"
 
         change_set = add_valve(p, 'v1', 'j1', 'j2', 10.0, VALVES_TYPE_FCV, 10.0, 10.0)
-        assert len(change_set.added) == 0
+        assert len(change_set.operations) == 0
 
         valves = get_links(p)
         assert len(valves) == 1
@@ -493,47 +523,53 @@ class TestApi:
         assert get_valve_minor_loss(p, 'v1') == 10.0
 
         change_set = set_valve_node1(p, 'v1', 'j2')
-        assert len(change_set.updated) == 0
+        assert len(change_set.operations) == 0
         change_set = set_valve_node2(p, 'v1', 'j1')
-        assert len(change_set.updated) == 0
+        assert len(change_set.operations) == 0
         change_set = set_valve_type(p, 'v1', "XXX")
-        assert len(change_set.updated) == 0
+        assert len(change_set.operations) == 0
 
         change_set = set_valve_node1(p, 'v1', 'j3')
-        assert len(change_set.updated) == 1
-        assert change_set.updated[0]['type'] == VALVE
-        assert change_set.updated[0]['id'] == 'v1'
-        assert change_set.updated[0]['property'] == 'node1'
+        assert len(change_set.operations) == 1
+        assert change_set.operations[0]['operation'] == 'update'
+        assert change_set.operations[0]['type'] == VALVE
+        assert change_set.operations[0]['id'] == 'v1'
+        assert change_set.operations[0]['property'] == 'node1'
 
         change_set = set_valve_node2(p, 'v1', 'j4')
-        assert len(change_set.updated) == 1
-        assert change_set.updated[0]['type'] == VALVE
-        assert change_set.updated[0]['id'] == 'v1'
-        assert change_set.updated[0]['property'] == 'node2'
+        assert len(change_set.operations) == 1
+        assert change_set.operations[0]['operation'] == 'update'
+        assert change_set.operations[0]['type'] == VALVE
+        assert change_set.operations[0]['id'] == 'v1'
+        assert change_set.operations[0]['property'] == 'node2'
 
         change_set = set_valve_diameter(p, 'v1', 100.0)
-        assert len(change_set.updated) == 1
-        assert change_set.updated[0]['type'] == VALVE
-        assert change_set.updated[0]['id'] == 'v1'
-        assert change_set.updated[0]['property'] == 'diameter'
+        assert len(change_set.operations) == 1
+        assert change_set.operations[0]['operation'] == 'update'
+        assert change_set.operations[0]['type'] == VALVE
+        assert change_set.operations[0]['id'] == 'v1'
+        assert change_set.operations[0]['property'] == 'diameter'
 
         change_set = set_valve_type(p, 'v1', VALVES_TYPE_GPV)
-        assert len(change_set.updated) == 1
-        assert change_set.updated[0]['type'] == VALVE
-        assert change_set.updated[0]['id'] == 'v1'
-        assert change_set.updated[0]['property'] == 'type'
+        assert len(change_set.operations) == 1
+        assert change_set.operations[0]['operation'] == 'update'
+        assert change_set.operations[0]['type'] == VALVE
+        assert change_set.operations[0]['id'] == 'v1'
+        assert change_set.operations[0]['property'] == 'type'
 
         change_set = set_valve_setting(p, 'v1', 100.0)
-        assert len(change_set.updated) == 1
-        assert change_set.updated[0]['type'] == VALVE
-        assert change_set.updated[0]['id'] == 'v1'
-        assert change_set.updated[0]['property'] == 'setting'
+        assert len(change_set.operations) == 1
+        assert change_set.operations[0]['operation'] == 'update'
+        assert change_set.operations[0]['type'] == VALVE
+        assert change_set.operations[0]['id'] == 'v1'
+        assert change_set.operations[0]['property'] == 'setting'
 
         change_set = set_valve_minor_loss(p, 'v1', 100.0)
-        assert len(change_set.updated) == 1
-        assert change_set.updated[0]['type'] == VALVE
-        assert change_set.updated[0]['id'] == 'v1'
-        assert change_set.updated[0]['property'] == 'minor_loss'
+        assert len(change_set.operations) == 1
+        assert change_set.operations[0]['operation'] == 'update'
+        assert change_set.operations[0]['type'] == VALVE
+        assert change_set.operations[0]['id'] == 'v1'
+        assert change_set.operations[0]['property'] == 'minor_loss'
 
         assert get_valve_node1(p, 'v1') == 'j3'
         assert get_valve_node2(p, 'v1') == 'j4'
@@ -543,30 +579,33 @@ class TestApi:
         assert get_valve_minor_loss(p, 'v1') == 100.0
 
         change_set = add_valve(p, 'v2', 'j1', 'j2', 10.0, VALVES_TYPE_FCV, 10.0, 10.0)
-        assert len(change_set.added) == 1
-        assert change_set.added[0]['type'] == VALVE
-        assert change_set.added[0]['id'] == "v2"
+        assert len(change_set.operations) == 1
+        assert change_set.operations[0]['operation'] == 'add'
+        assert change_set.operations[0]['type'] == VALVE
+        assert change_set.operations[0]['id'] == "v2"
 
         valves = get_links(p)
         assert len(valves) == 2
 
         change_set = delete_valve(p, 'v')
-        assert len(change_set.deleted) == 0
+        assert len(change_set.operations) == 0
 
         assert is_valve(p, 'v1')
 
         change_set = delete_valve(p, 'v1')
-        assert len(change_set.deleted) == 1
-        assert change_set.deleted[0]['type'] == VALVE
-        assert change_set.deleted[0]['id'] == "v1"
+        assert len(change_set.operations) == 1
+        assert change_set.operations[0]['operation'] == 'delete'
+        assert change_set.operations[0]['type'] == VALVE
+        assert change_set.operations[0]['id'] == "v1"
 
         valves = get_links(p)
         assert len(valves) == 1
 
         change_set = delete_valve(p, 'v2')
-        assert len(change_set.deleted) == 1
-        assert change_set.deleted[0]['type'] == VALVE
-        assert change_set.deleted[0]['id'] == "v2"
+        assert len(change_set.operations) == 1
+        assert change_set.operations[0]['operation'] == 'delete'
+        assert change_set.operations[0]['type'] == VALVE
+        assert change_set.operations[0]['id'] == "v2"
 
         self.leave(p)