diff --git a/exp/annotations.py b/exp/annotations.py
--- a/exp/annotations.py
+++ b/exp/annotations.py
@@ -6,10 +6,20 @@ import json
 from typing import MutableMapping
 
 from analyzer.epoint import EPoint
+from analyzer.corners import Corners
+
+
+class Board:
+	def __init__(self,**kwargs):
+		self.board=Corners(kwargs.get("board") or [])
+		self.grid=Corners(kwargs.get("grid") or [])
+
+	def isEmpty(self):
+		return len(self.board)==0 and len(self.grid)==0
 
 
 class DataFile(MutableMapping):
-	"""self._data: {filename: [EPoint,EPoint,EPoint,EPoint]}"""
+	"""self.data: {filename: [Board, ...}"""
 	def __init__(self,filename):
 		self.filename=filename
 		try:
@@ -25,11 +35,15 @@ class DataFile(MutableMapping):
 	def serialize(self,obj):
 		if isinstance(obj,EPoint):
 			return {"type": "EPoint", "val": [obj.x,obj.y]}
+		elif isinstance(obj,Board):
+			return {"type": "Board", "val": {"board": list(obj.board), "grid": list(obj.grid)}}
 		raise TypeError(obj)
 
 	def deserialize(self,obj):
-		if obj.get("type")!="EPoint": return obj
-		return EPoint(*obj["val"])
+		type=obj.get("type")
+		if type=="EPoint": return EPoint(*obj["val"])
+		elif type=="Board": return Board(**obj["val"])
+		return obj
 
 	def __getitem__(self, key): return self._data[key]
 	def __setitem__(self, key, val): self._data[key]=val