diff --git a/batch_command_records.py b/batch_command_records.py
index cfd6bbe..a3f7221 100644
--- a/batch_command_records.py
+++ b/batch_command_records.py
@@ -1,32 +1,41 @@
+from abc import ABC, abstractmethod
 from typing import Dict, Iterator, List, Type
 
 from command import Command, CommandRecord, CommandPending, CommandFinish
 from page import Page
 
 
-class BatchCommandRecords:
+class BatchCommandRecords(ABC):
     """Accessor for the CommandRecords of a StoredBatch."""
 
+    @abstractmethod
     def get_slice(self, offset: int, limit: int) -> List[CommandRecord]:
-        ...
+        """Get up to limit command records from the given offset."""
 
+    @abstractmethod
     def get_summary(self) -> Dict[Type[CommandRecord], int]:
-        ...
+        """Get the number of command records for each concrete type."""
 
+    @abstractmethod
     def stream_pages(self) -> Iterator[Page]:
-        ...
+        """Get a stream of all the pages touched by a batch."""
 
+    @abstractmethod
     def stream_commands(self) -> Iterator[Command]:
-        ...
+        """Get a stream of all the commands in a batch."""
 
+    @abstractmethod
     def make_plans_pending(self, offset: int, limit: int) -> List[CommandPending]:
-        ...
+        """Mark up to limit command records from the given offset as pending and return them."""
 
+    @abstractmethod
     def make_pendings_planned(self, command_record_ids: List[int]) -> None:
-        ...
+        """Mark the pending command records with the given IDs as planned."""
 
+    @abstractmethod
     def store_finish(self, command_finish: CommandFinish) -> None:
-        ...
+        """Save the given finished command."""
 
+    @abstractmethod
     def __len__(self) -> int:
-        ...
+        """Get the number of command records in the batch."""