diff --git a/examples/semantics/operational/port_models.py b/examples/semantics/operational/port_models.py
new file mode 100644
index 0000000..e30a11d
--- /dev/null
+++ b/examples/semantics/operational/port_models.py
@@ -0,0 +1,302 @@
+# Design meta-model
+port_mm_cs = """
+    Source:Class {
+        abstract = True;
+    }
+    Sink:Class {
+        abstract = True;
+    }
+
+    Place:Class
+    :Inheritance (Place -> Source)
+    :Inheritance (Place -> Sink)
+
+    connection:Association (Source -> Sink)
+
+    CapacityConstraint:Class
+
+    CapacityConstraint_shipCapacity:AttributeLink (CapacityConstraint -> Integer) {
+        name = "shipCapacity";
+        optional = False;
+
+        # cannot have negative capacity:
+        constraint = `get_value(get_target(this)) >= 0`; # non-negative
+    }
+
+    # Capacity 
+    capacityOf:Association (CapacityConstraint -> Place) {
+        # must say something about at least one Place, otherwise what is the point of the constraint?
+        target_lower_cardinality = 1;
+    }
+
+    Berth:Class
+    :Inheritance (Berth -> Place)
+
+    # Set of workers
+    WorkerSet:Class
+
+    WorkerSet_numWorkers:AttributeLink (WorkerSet -> Integer) {
+        name = "numWorkers";
+        optional = False;
+        constraint = `get_value(get_target(this)) >= 0`; # non-negative
+    }
+    canOperate:Association (WorkerSet -> Berth) {
+        target_lower_cardinality = 1;
+    }
+
+    Generator:Class
+    :Inheritance (Generator -> Source)
+
+    BlackHole:Class
+    :Inheritance (BlackHole -> Sink)
+
+
+    # Those classes to which we want to attach a runtime state object
+    Stateful:Class {
+        abstract = True;
+    }
+    :Inheritance (Place      -> Stateful)
+    :Inheritance (BlackHole  -> Stateful)
+    :Inheritance (WorkerSet  -> Stateful)
+    :Inheritance (Berth      -> Stateful)
+    :Inheritance (connection -> Stateful)
+""";
+
+# Runtime meta-model
+port_rt_mm_cs = port_mm_cs + """
+    State:Class
+    of:Association (State -> Stateful) {
+        source_lower_cardinality = 1;
+        source_upper_cardinality = 1;
+        target_lower_cardinality = 1;
+        target_upper_cardinality = 1;
+    }
+
+    PlaceState:Class
+    :Inheritance (PlaceState -> State)
+
+    PlaceState_numShips:AttributeLink (PlaceState -> Integer) {
+        # number of ships currently in the place
+        name = "numShips";
+        optional = False;
+        constraint = `get_value(get_target(this)) >= 0`; # non-negative
+    }
+
+    shipCapacities:GlobalConstraint {
+        constraint = ```
+            errors = []
+            for _, constr in get_all_instances("CapacityConstraint"):
+                cap = get_slot_value(constr, "shipCapacity")
+                total = 0
+                place_names = [] # for debugging
+                for lnk in get_outgoing(constr, "capacityOf"):
+                    place = get_target(lnk)
+                    place_names.append(get_name(place))
+                    place_state = get_source(get_incoming(place, "of")[0])
+                    total += get_slot_value(place_state, "numShips")
+                if total > cap:
+                    errors.append(f"The number of ships in places {','.join(place_names)} ({total}) exceeds the capacity ({cap}) of CapacityConstraint {get_name(constr)}.")
+            errors
+        ```;
+    }
+
+    BerthState:Class {
+        # status == empty <=> numShips == 0
+        constraint = `(get_slot_value(this, "numShips") == 0) == (get_slot_value(this, "status") == "empty")`;
+    }
+    :Inheritance (BerthState -> PlaceState)
+
+    BerthState_status:AttributeLink (BerthState -> String) {
+        name = "status";
+        optional = False;
+        constraint = `(
+            get_value(get_target(this)) in { "empty", "unserved", "served" }
+        )`;
+    }
+
+    WorkerSetState:Class
+    :Inheritance (WorkerSetState -> State)
+
+    isOperating:Association (WorkerSetState -> Berth) {
+        constraint = ```
+            errors = []
+
+            # get status of Berth
+            berth = get_target(this)
+            berth_state = get_source(get_incoming(berth, "of")[0])
+            status = get_slot_value(berth_state, "status")
+            if status != "unserved":
+                errors.append(f"Cannot operate {get_name(berth)} because there is no unserved ship there.")
+
+            # only operate Berts that we can operate
+            workerset = get_target(get_outgoing(get_source(this), "of")[0])
+            can_operate = [get_target(lnk) for lnk in get_outgoing(workerset, "canOperate")]
+            if berth not in can_operate:
+                errors.append(f"Cannot operate {get_name(berth)}.")
+
+            errors
+        ```;
+    }
+
+    operatingCapacities:GlobalConstraint {
+        constraint = ```
+            errors = []
+            for _, workersetstate in get_all_instances("WorkerSetState"):
+                workerset = get_target(get_outgoing(workersetstate, "of")[0])
+                num_operating = len(get_outgoing(workersetstate, "isOperating"))
+                num_workers = get_slot_value(workerset, "numWorkers")
+                if num_operating > num_workers:
+                    errors.append(f"WorkerSet {get_name(workerset)} is operating more berths ({num_operating}) than there are workers ({num_workers})")
+            errors
+        ```;
+    }
+
+    ConnectionState:Class
+    :Inheritance (ConnectionState -> State)
+    ConnectionState_moved:AttributeLink (ConnectionState -> Boolean) {
+        name = "moved";
+        optional = False;
+        constraint = ```
+            all_successors_moved = True
+            moved = get_value(get_target(this))
+            conn_state = get_source(this)
+            conn = get_target(get_outgoing(conn_state, "of")[0])
+            tgt_place = get_target(conn)
+            next_conns = get_outgoing(tgt_place, "connection")
+            for next_conn in next_conns:
+                next_conn_state = get_source(get_incoming(next_conn, "of")[0])
+                if not get_slot_value(next_conn_state, "moved"):
+                    all_successors_moved = False
+            not moved or all_successors_moved
+        ```;
+    }
+
+    BlackHoleState:Class
+    :Inheritance (BlackHoleState -> State)
+    BlackHoleState_counter:AttributeLink (BlackHoleState -> Integer) {
+        name = "counter";
+        optional = False;
+        constraint = `get_value(get_target(this)) >= 0`; # non-negative
+    }
+
+    Clock:Class {
+        lower_cardinality = 1;
+        upper_cardinality = 1;
+    }
+    Clock_time:AttributeLink (Clock -> Integer) {
+        name = "time";
+        optional = False;
+        constraint = `get_value(get_target(this)) >= 0`;
+    }
+"""
+
+# Design model: the part that doesn't change
+port_m_cs = """
+    gen:Generator
+
+    # newly arrive ships collect here
+    waiting:Place
+    c1:connection (gen -> waiting)
+
+    inboundPassage:Place
+    c2:connection (waiting -> inboundPassage)
+
+    outboundPassage:Place
+
+    # inboundPassage and outboundPassage cannot have more than 3 ships total
+    passageCap:CapacityConstraint {
+        shipCapacity = 3;
+    }
+    :capacityOf (passageCap -> inboundPassage)
+    :capacityOf (passageCap -> outboundPassage)
+
+
+    # Berth 1
+
+    inboundBerth1:Place
+    berth1:Berth
+    outboundBerth1:Place
+
+    inboundBerth1Cap:CapacityConstraint { shipCapacity = 1; }
+    :capacityOf (inboundBerth1Cap -> inboundBerth1)
+    outboundBerth1Cap:CapacityConstraint { shipCapacity = 1; }
+    :capacityOf (outboundBerth1Cap -> outboundBerth1)
+
+    berth1Cap:CapacityConstraint { shipCapacity = 1; }
+    :capacityOf (berth1Cap -> berth1)
+
+    c3:connection (inboundBerth1 -> berth1)
+    c4:connection (berth1 -> outboundBerth1)
+
+    # Berth 2
+
+    inboundBerth2:Place
+    berth2:Berth
+    outboundBerth2:Place
+
+    inboundBerth2Cap:CapacityConstraint { shipCapacity = 1; }
+    :capacityOf (inboundBerth2Cap -> inboundBerth2)
+    outboundBerth2Cap:CapacityConstraint { shipCapacity = 1; }
+    :capacityOf (outboundBerth2Cap -> outboundBerth2)
+
+    berth2Cap:CapacityConstraint { shipCapacity = 1; }
+    :capacityOf (berth2Cap -> berth2)
+
+    c5:connection (inboundBerth2 -> berth2)
+    c6:connection (berth2 -> outboundBerth2)
+
+
+    # can either go to Berth 1 or Berth 2
+    c7:connection (inboundPassage -> inboundBerth1)
+    c8:connection (inboundPassage -> inboundBerth2)
+
+    c9:connection (outboundBerth1 -> outboundPassage)
+    c10:connection (outboundBerth2 -> outboundPassage)
+
+
+    # ships that have been served are counted here
+    served:BlackHole
+    c11:connection (outboundPassage -> served)
+
+
+    workers:WorkerSet {
+        numWorkers = 1;
+    }
+    :canOperate (workers -> berth1)
+    :canOperate (workers -> berth2)
+"""
+
+# Initial runtime model: the part that changes (every execution step)
+port_rt_m_cs = port_m_cs + """
+    clock:Clock {
+        time = 0;
+    }
+
+    waitingState:PlaceState         { numShips = 2; }  :of (waitingState -> waiting)
+    inboundPassageState:PlaceState  { numShips = 0; }  :of (inboundPassageState -> inboundPassage)
+    outboundPassageState:PlaceState { numShips = 0; }  :of (outboundPassageState -> outboundPassage)
+
+    inboundBerth1State:PlaceState   { numShips = 0; }  :of (inboundBerth1State -> inboundBerth1)
+    outboundBerth1State:PlaceState  { numShips = 0; }  :of (outboundBerth1State -> outboundBerth1)
+    inboundBerth2State:PlaceState   { numShips = 0; }  :of (inboundBerth2State -> inboundBerth2)
+    outboundBerth2State:PlaceState  { numShips = 0; }  :of (outboundBerth2State -> outboundBerth2)
+
+    berth1State:BerthState { status = "empty"; numShips = 0; }  :of (berth1State -> berth1)
+    berth2State:BerthState { status = "empty"; numShips = 0; }  :of (berth2State -> berth2)
+
+    servedState:BlackHoleState { counter = 0; }  :of (servedState -> served)
+
+    workersState:WorkerSetState  :of (workersState -> workers)
+
+    c1S:ConnectionState  { moved = False; }   :of (c1S -> c1)
+    c2S:ConnectionState  { moved = False; }   :of (c2S -> c2)
+    c3S:ConnectionState  { moved = False; }   :of (c3S -> c3)
+    c4S:ConnectionState  { moved = False; }   :of (c4S -> c4)
+    c5S:ConnectionState  { moved = False; }   :of (c5S -> c5)
+    c6S:ConnectionState  { moved = False; }   :of (c6S -> c6)
+    c7S:ConnectionState  { moved = False; }   :of (c7S -> c7)
+    c8S:ConnectionState  { moved = False; }   :of (c8S -> c8)
+    c9S:ConnectionState  { moved = False; }   :of (c9S -> c9)
+    c10S:ConnectionState { moved = False; }   :of (c10S -> c10)
+    c11S:ConnectionState { moved = False; }   :of (c11S -> c11)
+"""