diff --git a/learnware/specification/__init__.py b/learnware/specification/__init__.py
index 4d8b1b6..7655320 100644
--- a/learnware/specification/__init__.py
+++ b/learnware/specification/__init__.py
@@ -1,3 +1,3 @@
 from .utils import generate_stat_spec
-from .base import Specification, StatSpecification
+from .base import Specification, BaseStatSpecification
 from .rkme import RKMESpecification
\ No newline at end of file
diff --git a/learnware/specification/base.py b/learnware/specification/base.py
index 3d96fa0..c2060f3 100644
--- a/learnware/specification/base.py
+++ b/learnware/specification/base.py
@@ -10,17 +10,29 @@ class Specification:
 
     def get_property(self):
         return self.property
+    
+    def add_stat_spec(self, name, new_stat_spec:BaseStatSpecification):
+        self.stat_spec[name] = new_stat_spec
+    
+    def get_stat_spec_by_name(self, name:str):
+        if not name in self.stat_spec:
+            return None
+        
+        return self.stat_spec[name]
 
     def update_stat_spec(self): # update specification method
         pass
 
-class StatSpecification:
+class BaseStatSpecification:
+    def __init__(self):
+        pass
+
     def generate_stat_spec_from_data(self, X: np.ndarray):
         raise NotImplementedError("generate_stat_spec_from_data is not implemented")
 
-    def save(self, filepath: str = "./stat_spec.npy"):
+    def save(self, filepath: str):
         raise NotImplementedError("save is not implemented")
 
 
-    def load(self, filepath: str = "./stat_spec.npy"):
+    def load(self, filepath: str):
         raise NotImplementedError("load is not implemented")