diff --git a/AlgebraicDataflowArchitectureModel/src/models/controlFlowModel/CallGraph.java b/AlgebraicDataflowArchitectureModel/src/models/controlFlowModel/CallGraph.java
index 8bd6310..af56ad6 100644
--- a/AlgebraicDataflowArchitectureModel/src/models/controlFlowModel/CallGraph.java
+++ b/AlgebraicDataflowArchitectureModel/src/models/controlFlowModel/CallGraph.java
@@ -10,6 +10,9 @@
 import java.util.Map;
 import java.util.Set;
 
+/**
+ * {@link CallGraph} is a directed graph that represents the control flow between resources
+ */
 public class CallGraph extends DirectedGraph {
 	protected Map<ResourceNode, StatefulObjectNode> statefulObjMap;
 	
@@ -17,6 +20,11 @@
 		statefulObjMap = new HashMap<>();
 	}
 	
+	/**
+	 * Add a node to the graph.
+	 *
+	 * @param node The node to be added.
+	 */
 	public void addNode(Node node) {
 		if (node instanceof ResourceNode) {
 			ResourceNode resNode = (ResourceNode) node;
@@ -37,12 +45,27 @@
 		}
 	}
 	
+	/**
+	 * Add new call edge from {@code srcResNode} to {@code dstResNode} with PUSH / PULL selection.
+	 *
+	 * @param srcResNode     The resource node the edge starts from.
+	 * @param dstResNode     The resource node the edge ends at.
+	 * @param selectedOption PUSH / PULL
+	 */
 	public void addEdge(ResourceNode srcResNode, ResourceNode dstResNode, PushPullValue selectedOption) {
 		addNode(srcResNode);
 		addNode(dstResNode);
 		addEdge(new CallEdge(getStatefulObjectNode(srcResNode), getStatefulObjectNode(dstResNode), selectedOption));
 	}
 	
+	/**
+	 * Insert an edge into the graph.
+	 *
+	 * @param srcObjNode     The source node of the edge to be inserted
+	 * @param dstObjNode     The destination node of the edge to be inserted
+	 * @param selectedOption PUSH or PULL
+	 * @param n              The calling order of the edge
+	 */
 	public void insertEdge(ObjectNode srcObjNode, ObjectNode dstObjNode, PushPullValue selectedOption, int n) {
 		CallEdge edge = new CallEdge(srcObjNode, dstObjNode, selectedOption);
 		simpleAddEdge(edge);
@@ -59,7 +82,7 @@
 	public Set<Node> getRootNodes() {
 		Set<Node> roots = new HashSet<>(getNodes());
 		for (Node n : getNodes()) {
-			roots.removeAll(n.getSuccessors());
+			roots.removeAll(n.getSuccessors()); // Remove all child nodes of each node in the graph
 		}
 		return roots;
 	}