diff --git a/b_asic/operation.py b/b_asic/operation.py
index 731822f1d0cbc06e5ad244c878c5dbaf8847b905..afe1df7916203bf48c43feb3c1f7e55ab283557d 100644
--- a/b_asic/operation.py
+++ b/b_asic/operation.py
@@ -11,23 +11,12 @@ if TYPE_CHECKING:
 	from b_asic.port import InputPort, OutputPort
 	from b_asic.simulation import SimulationState
 
-OperationId = NewType("OperationId", int)
-
-
 class Operation(ABC):
 	"""
 	Operation interface.
 	TODO: More info.
 	"""
 
-	@abstractmethod
-	def identifier(self) -> OperationId:
-		"""
-		Get the unique identifier.
-		TODO: Move id info to SFG, remove id class members.
-		"""
-		pass
-
 	@abstractmethod
 	def inputs(self) -> "List[InputPort]":
 		"""
diff --git a/b_asic/signal_flow_graph.py b/b_asic/signal_flow_graph.py
index f9671636dd345fadfebd2a116a9add2466615db8..3c709ab3a57b9c81b455630f89f315341e602384 100644
--- a/b_asic/signal_flow_graph.py
+++ b/b_asic/signal_flow_graph.py
@@ -3,11 +3,14 @@ B-ASIC Signal Flow Graph Module.
 TODO: More info.
 """
 
-from b_asic.operation import OperationId, Operation
+from b_asic.operation import Operation
 from b_asic.basic_operation import BasicOperation
 from b_asic.signal import SignalSource, SignalDestination
 from b_asic.simulation import SimulationState, OperationState
-from typing import List
+from typing import List, Dict
+
+# Types
+OperationId = NewType("OperationId", int)
 
 
 class SFG(BasicOperation):
@@ -16,7 +19,7 @@ class SFG(BasicOperation):
 	TODO: More info.
 	"""
 
-	_operations: List[Operation]
+	_operations: Dict[OperationID, Operation]
 
 	def __init__(self, identifier: OperationId, input_destinations: List[SignalDestination], output_sources: List[SignalSource]):
 		"""
@@ -24,7 +27,9 @@ class SFG(BasicOperation):
 		"""
 		super().__init__(identifier)
 		# TODO: Allocate input/output ports with appropriate IDs.
-		self._operations = []
+		
+		self._operations = dict # Map Operation ID to Operation objects
+
 		# TODO: Traverse the graph between the inputs/outputs and add to self._operations.
 		# TODO: Connect ports with signals with appropriate IDs.