import com.google.common.base.Optional;
+/**
+ * Internal interface representing a modification action of a particular node.
+ * It is used by the validation code to allow for a read-only view of the
+ * modification tree as we should never modify that during validation.
+ */
interface NodeModification extends Identifiable<PathArgument> {
+ /**
+ * Get the type of modification.
+ *
+ * @return Modification type.
+ */
ModificationType getType();
+
+ /**
+ * Get the original tree node to which the modification is to be applied.
+ *
+ * @return The original node, or {@link Optional#absent()} if the node is
+ * a new node.
+ */
Optional<TreeNode> getOriginal();
+
+ /**
+ * Get a read-only view of children nodes.
+ *
+ * @return Iterable of all children nodes.
+ */
Iterable<? extends NodeModification> getChildren();
}