diff --git a/app/api/views/upload/dataset.py b/app/api/views/upload/dataset.py
index 26d6735f..097b4078 100644
--- a/app/api/views/upload/dataset.py
+++ b/app/api/views/upload/dataset.py
@@ -1,11 +1,13 @@
 import csv
 import json
+from itertools import chain
 from typing import Dict, Iterator, List, Optional, Type
 
 import pyexcel
 
 from .data import BaseData
 from .label import Label
+from .labels import Labels
 
 
 class Record:
@@ -15,23 +17,41 @@ class Record:
                  label: List[Label] = None):
         if label is None:
             label = []
-        self.data = data
-        self.label = label
+        self._data = data
+        self._label = label
 
     def __str__(self):
-        return f'{self.data}\t{self.label}'
+        return f'{self._data}\t{self._label}'
 
-    def dict(self):
-        label_names = [
-            {
-                'text': label.name
-            } for label in self.label if label.has_name()
+    @property
+    def data(self):
+        return self._data
+
+    @property
+    def annotation(self):
+        return Labels(self._label)
+
+    @property
+    def label(self):
+        return [label.name for label in self._label if label.has_name()]
+
+
+class Records:
+
+    def __init__(self, records: List[Record]):
+        self.records = records
+
+    def data(self):
+        return [r.data.dict() for r in self.records]
+
+    def annotation(self, mapping: Dict[str, int]):
+        return [r.annotation.replace_label(mapping).dict() for r in self.records]
+
+    def label(self):
+        labels = set(chain(*[r.label for r in self.records]))
+        return [
+            {'text': label} for label in labels
         ]
-        return {
-            'data': self.data.dict(),
-            'annotation': [label.dict() for label in self.label],
-            'label': label_names
-        }
 
 
 class Dataset:
@@ -41,21 +61,26 @@ class Dataset:
                  data_class: Type[BaseData],
                  label_class: Type[Label],
                  encoding: Optional[str] = None,
-                 column_data: str = 'text',
-                 column_label: str = 'label',
                  **kwargs):
         self.filenames = filenames
         self.data_class = data_class
         self.label_class = label_class
         self.encoding = encoding
-        self.column_data = column_data
-        self.column_label = column_label
         self.kwargs = kwargs
 
     def __iter__(self) -> Iterator[Record]:
         for filename in self.filenames:
             yield from self.load(filename)
 
+    def batch(self, batch_size) -> Records:
+        records = []
+        for record in self:
+            records.append(record)
+            if len(records) == batch_size:
+                yield Records(records)
+                records = []
+        yield Records(records)
+
     def load(self, filename: str) -> Iterator[Record]:
         """Loads a file content."""
         with open(filename, encoding=self.encoding) as f:
@@ -64,8 +89,8 @@ class Dataset:
             yield record
 
     def from_row(self, filename: str, row: Dict) -> Record:
-        text = row.pop(self.column_data)
-        label = row.pop(self.column_label, [])
+        text = row.pop(self.kwargs.get('column_data', 'text'))
+        label = row.pop(self.kwargs.get('column_label', 'label'), [])
         label = [label] if isinstance(label, str) else label
         label = [self.label_class.parse(o) for o in label]
         data = self.data_class.parse(text=text, filename=filename, metadata=row)