diff --git a/dpgen2/exploration/task/__init__.py b/dpgen2/exploration/task/__init__.py
index 602618d7..19562255 100644
--- a/dpgen2/exploration/task/__init__.py
+++ b/dpgen2/exploration/task/__init__.py
@@ -25,6 +25,6 @@
     ExplorationTask,
 )
 from .task_group import (
+    BaseExplorationTaskGroup,
     ExplorationTaskGroup,
-    ExplorationTaskGroupData,
 )
diff --git a/dpgen2/exploration/task/stage.py b/dpgen2/exploration/task/stage.py
index dd281f26..a039f947 100644
--- a/dpgen2/exploration/task/stage.py
+++ b/dpgen2/exploration/task/stage.py
@@ -16,8 +16,8 @@
     ExplorationTask,
 )
 from .task_group import (
+    BaseExplorationTaskGroup,
     ExplorationTaskGroup,
-    ExplorationTaskGroupData,
 )
 
 
@@ -68,7 +68,7 @@ def make_task(
 
         """
 
-        lmp_task_grp = ExplorationTaskGroupData()
+        lmp_task_grp = BaseExplorationTaskGroup()
         for ii in self.explor_groups:
             # lmp_task_grp.add_group(ii.make_task())
             lmp_task_grp += ii.make_task()
diff --git a/dpgen2/exploration/task/task_group.py b/dpgen2/exploration/task/task_group.py
index 964a9cd3..f9d320e7 100644
--- a/dpgen2/exploration/task/task_group.py
+++ b/dpgen2/exploration/task/task_group.py
@@ -16,7 +16,7 @@
 )
 
 
-class ExplorationTaskGroup(Sequence):
+class BaseExplorationTaskGroup(Sequence):
     """A group of exploration tasks. Implemented as a `list` of `ExplorationTask`."""
 
     def __init__(self):
@@ -60,21 +60,15 @@ def __add__(
         """Add another group to the group."""
         return self.add_group(group)
 
-    @abstractmethod
-    def make_task(self) -> "ExplorationTaskGroup":
-        """Make the task group."""
-        pass
-
-
-class ExplorationTaskGroupData(ExplorationTaskGroup):
-    """Data-only exploration task group."""
 
+class ExplorationTaskGroup(ABC, BaseExplorationTaskGroup):
     def __init__(self):
         super().__init__()
 
-    def make_task(self):
+    @abstractmethod
+    def make_task(self) -> "ExplorationTaskGroup":
         """Make the task group."""
-        raise NotImplementedError("This class is not supposed to supply make_task")
+        pass
 
 
 class FooTask(ExplorationTask):
diff --git a/tests/test_prep_run_lmp.py b/tests/test_prep_run_lmp.py
index 6960878f..1aca5000 100644
--- a/tests/test_prep_run_lmp.py
+++ b/tests/test_prep_run_lmp.py
@@ -69,8 +69,8 @@
     train_task_pattern,
 )
 from dpgen2.exploration.task import (
+    BaseExplorationTaskGroup,
     ExplorationTask,
-    ExplorationTaskGroupData,
 )
 from dpgen2.op.prep_lmp import (
     PrepLmp,
@@ -90,7 +90,7 @@
 
 
 def make_task_group_list(ngrp, ntask_per_grp):
-    tgrp = ExplorationTaskGroupData()
+    tgrp = BaseExplorationTaskGroup()
     for ii in range(ngrp):
         for jj in range(ntask_per_grp):
             tt = ExplorationTask()