diff --git a/midas/checker/types.py b/midas/checker/types.py
new file mode 100644
index 0000000..71765ad
--- /dev/null
+++ b/midas/checker/types.py
@@ -0,0 +1,29 @@
+from __future__ import annotations
+
+from dataclasses import dataclass
+
+
+@dataclass(frozen=True, kw_only=True)
+class BaseType:
+    name: str
+
+
+@dataclass(frozen=True, kw_only=True)
+class SimpleType:
+    base: BaseType
+
+
+@dataclass(frozen=True, kw_only=True)
+class Operation:
+    left: Type
+    operator: str
+    right: Type
+    result: Type
+
+
+@dataclass(frozen=True, kw_only=True)
+class UnknownType:
+    pass
+
+
+Type = BaseType | SimpleType | UnknownType