diff --git a/src/lib.rs b/src/lib.rs
index fa3e909..602a254 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -162,6 +162,14 @@ impl std::ops::Index<&ClassId> for EGraph {
     }
 }
 
+#[cfg_attr(feature = "serde", derive(serde::Deserialize, serde::Serialize))]
+#[derive(Debug, Default, Clone, Hash, PartialEq, Eq, PartialOrd, Ord)]
+pub struct NodeData {
+    //
+    #[cfg_attr(feature = "serde", serde(default))]
+    pub subsumed: bool,
+}
+
 #[cfg_attr(feature = "serde", derive(serde::Deserialize, serde::Serialize))]
 #[derive(Clone, Debug, PartialEq, Eq, Hash, PartialOrd, Ord)]
 pub struct Node {
@@ -171,6 +179,9 @@ pub struct Node {
     pub eclass: ClassId,
     #[cfg_attr(feature = "serde", serde(default = "one"))]
     pub cost: Cost,
+    // Optional data about the node
+    #[cfg_attr(feature = "serde", serde(default))]
+    pub data: NodeData,
 }
 
 impl Node {