diff --git a/MANIFEST.in b/MANIFEST.in
index 1aba38f..42eb410 100644
--- a/MANIFEST.in
+++ b/MANIFEST.in
@@ -1 +1 @@
-include LICENSE
+include LICENSE.txt
diff --git a/README.md b/README.md
index 12deb50..d112b48 100644
--- a/README.md
+++ b/README.md
@@ -34,14 +34,15 @@ max    400140.000000     246.000000       5.000000
 
 ## Connecting to Elasticsearch Cloud
 
-```python
+```
+>>> import eland as ed
+>>> from elasticsearch import Elasticsearch
+
 >>> es = Elasticsearch(cloud_id="<cloud_id>", http_auth=('<user>','<password>'))
 
 >>> es.info()
 {'name': 'instance-0000000000', 'cluster_name': 'bf900cfce5684a81bca0be0cce5913bc', 'cluster_uuid': 'xLPvrV3jQNeadA7oM4l1jA', 'version': {'number': '7.4.2', 'build_flavor': 'default', 'build_type': 'tar', 'build_hash': '2f90bbf7b93631e52bafb59b3b049cb44ec25e96', 'build_date': '2019-10-28T20:40:44.881551Z', 'build_snapshot': False, 'lucene_version': '8.2.0', 'minimum_wire_compatibility_version': '6.8.0', 'minimum_index_compatibility_version': '6.0.0-beta1'}, 'tagline': 'You Know, for Search'}
 
->>> import eland as ed
-
 >>> df = ed.read_es(es, 'reviews')
 ```
 
diff --git a/eland/actions.py b/eland/actions.py
new file mode 100644
index 0000000..286726d
--- /dev/null
+++ b/eland/actions.py
@@ -0,0 +1,87 @@
+from abc import ABC, abstractmethod
+
+# -------------------------------------------------------------------------------------------------------------------- #
+# PostProcessingActions                                                                                                #
+# -------------------------------------------------------------------------------------------------------------------- #
+class PostProcessingAction(ABC):
+    def __init__(self, action_type):
+        """
+        Abstract class for postprocessing actions
+
+        Parameters
+        ----------
+            action_type: str
+                The action type (e.g. sort_index, head etc.)
+        """
+        self._action_type = action_type
+
+    @property
+    def type(self):
+        return self._action_type
+
+    @abstractmethod
+    def resolve_action(self, df):
+        pass
+
+    @abstractmethod
+    def __repr__(self):
+        pass
+
+class SortIndexAction(PostProcessingAction):
+    def __init__(self):
+        super().__init__("sort_index")
+
+    def resolve_action(self, df):
+        return df.sort_index()
+
+    def __repr__(self):
+        return "('{}')".format(self.type)
+
+class HeadAction(PostProcessingAction):
+    def __init__(self, count):
+        super().__init__("head")
+
+        self._count = count
+
+    def resolve_action(self, df):
+        return df.head(self._count)
+
+    def __repr__(self):
+        return "('{}': ('count': {}))".format(self.type, self._count)
+
+
+class TailAction(PostProcessingAction):
+    def __init__(self, count):
+        super().__init__("tail")
+
+        self._count = count
+
+    def resolve_action(self, df):
+        return df.tail(self._count)
+
+    def __repr__(self):
+        return "('{}': ('count': {}))".format(self.type, self._count)
+
+
+class SortFieldAction(PostProcessingAction):
+    def __init__(self, sort_params_string):
+        super().__init__("sort_field")
+
+        if sort_params_string is None:
+            raise ValueError("Expected valid string")
+
+        # Split string
+        sort_params = sort_params_string.split(":")
+        if len(sort_params) != 2:
+            raise ValueError("Expected ES sort params string (e.g. _doc:desc). Got '{}'".format(sort_params_string))
+
+        self._sort_field = sort_params[0]
+        self._sort_order = Operations.SortOrder.from_string(sort_params[1])
+
+    def resolve_action(self, df):
+        if self._sort_order == Operations.SortOrder.ASC:
+            return df.sort_values(self._sort_field, True)
+        return df.sort_values(self._sort_field, False)
+
+    def __repr__(self):
+        return "('{}': ('sort_field': '{}', 'sort_order': {}))".format(self.type, self._sort_field, self._sort_order)
diff --git a/eland/dataframe.py b/eland/dataframe.py
index 2f01aef..6f7707d 100644
--- a/eland/dataframe.py
+++ b/eland/dataframe.py
@@ -385,12 +385,14 @@ class DataFrame(NDFrame):
         <BLANKLINE>
         [27 rows x 5 columns]
         Operations:
-         tasks: [('boolean_filter', {'bool': {'must': [{'term': {'OriginAirportID': 'AMS'}}, {'range': {'FlightDelayMin': {'gt': 60}}}]}}), ('field_names', ['timestamp', 'OriginAirportID', 'DestAirportID', 'FlightDelayMin']), ('tail', ('_doc', 5))]
+         tasks: [('boolean_filter': ('boolean_filter': {'bool': {'must': [{'term': {'OriginAirportID': 'AMS'}}, {'range': {'FlightDelayMin': {'gt': 60}}}]}})), ('tail': ('sort_field': '_doc', 'count': 5))]
          size: 5
          sort_params: _doc:desc
          _source: ['timestamp', 'OriginAirportID', 'DestAirportID', 'FlightDelayMin']
          body: {'query': {'bool': {'must': [{'term': {'OriginAirportID': 'AMS'}}, {'range': {'FlightDelayMin': {'gt': 60}}}]}}, 'aggs': {}}
-         post_processing: ['sort_index']
+         post_processing: [('sort_index')]
+        'field_to_display_names': {}
+        'display_to_field_names': {}
         <BLANKLINE>
         """
         buf = StringIO()
diff --git a/eland/ndframe.py b/eland/ndframe.py
index 6a7ddeb..5d6fd61 100644
--- a/eland/ndframe.py
+++ b/eland/ndframe.py
@@ -1,7 +1,7 @@
 """
 NDFrame
 ---------
-Base class for eland.DataFrame and eland.Series.
+Abstract base class for eland.DataFrame and eland.Series.
 
 The underlying data resides in Elasticsearch and the API aligns as much as
 possible with pandas APIs.
@@ -24,6 +24,7 @@ only Elasticsearch aggregatable fields can be aggregated or grouped.
 """
 
 import sys
+from abc import ABC
 
 import pandas as pd
 from pandas.core.dtypes.common import is_list_like
@@ -32,7 +33,7 @@ from pandas.util._validators import validate_bool_kwarg
 from eland import ElandQueryCompiler
 
 
-class NDFrame:
+class NDFrame(ABC):
 
     def __init__(self,
                  client=None,
diff --git a/eland/operations.py b/eland/operations.py
index 5868854..9b1fc44 100644
--- a/eland/operations.py
+++ b/eland/operations.py
@@ -1,11 +1,12 @@
 import copy
-from enum import Enum
 
-import numpy as np
 import pandas as pd
 
 from eland import Index
 from eland import Query
+from eland.actions import SortFieldAction
+from eland.tasks import HeadTask, TailTask, BooleanFilterTask, ArithmeticOpFieldsTask, QueryTermsTask, \
+    QueryIdsTask, SortOrder, SizeTask
 
 
 class Operations:
@@ -20,87 +21,46 @@ class Operations:
     This is maintained as a 'task graph' (inspired by dask)
     (see https://docs.dask.org/en/latest/spec.html)
     """
-
-    class SortOrder(Enum):
-        ASC = 0
-        DESC = 1
-
-        @staticmethod
-        def reverse(order):
-            if order == Operations.SortOrder.ASC:
-                return Operations.SortOrder.DESC
-
-            return Operations.SortOrder.ASC
-
-        @staticmethod
-        def to_string(order):
-            if order == Operations.SortOrder.ASC:
-                return "asc"
-
-            return "desc"
-
-        @staticmethod
-        def from_string(order):
-            if order == "asc":
-                return Operations.SortOrder.ASC
-
-            return Operations.SortOrder.DESC
-
-    def __init__(self, tasks=None):
+    def __init__(self, tasks=None, field_names=None):
         if tasks is None:
             self._tasks = []
         else:
             self._tasks = tasks
+        self._field_names = field_names
 
     def __constructor__(self, *args, **kwargs):
         return type(self)(*args, **kwargs)
 
     def copy(self):
-        return self.__constructor__(tasks=copy.deepcopy(self._tasks))
+        return self.__constructor__(tasks=copy.deepcopy(self._tasks), field_names=copy.deepcopy(self._field_names))
 
     def head(self, index, n):
         # Add a task that is an ascending sort with size=n
-        task = ('head', (index.sort_field, n))
+        task = HeadTask(index.sort_field, n)
         self._tasks.append(task)
 
     def tail(self, index, n):
         # Add a task that is descending sort with size=n
-        task = ('tail', (index.sort_field, n))
+        task = TailTask(index.sort_field, n)
         self._tasks.append(task)
 
     def arithmetic_op_fields(self, field_name, op_name, left_field, right_field, op_type=None):
-        if op_type:
-            task = ('arithmetic_op_fields', (field_name, (op_name, (left_field, right_field))), op_type)
-        else:
-            task = ('arithmetic_op_fields', (field_name, (op_name, (left_field, right_field))))
         # Set this as a column we want to retrieve
         self.set_field_names([field_name])
 
+        task = ArithmeticOpFieldsTask(field_name, op_name, left_field, right_field, op_type)
         self._tasks.append(task)
 
     def set_field_names(self, field_names):
-        # Setting field_names at different phases of the task list may result in different
-        # operations. So instead of setting field_names once, set when it happens in call chain
         if not isinstance(field_names, list):
             field_names = list(field_names)
 
-        # TODO - field_name renaming
-        # TODO - validate we are setting field_names to a subset of last field_names?
-        task = ('field_names', field_names)
-        self._tasks.append(task)
-        # Iterate backwards through task list looking for last 'field_names' task
-        for task in reversed(self._tasks):
-            if task[0] == 'field_names':
-                return task[1]
-        return None
+        self._field_names = field_names
+
+        return self._field_names
 
     def get_field_names(self):
-        # Iterate backwards through task list looking for last 'field_names' task
-        for task in reversed(self._tasks):
-            if task[0] == 'field_names':
-                return task[1]
-
-        return None
+        return self._field_names
 
     def __repr__(self):
         return repr(self._tasks)
@@ -248,7 +208,9 @@ class Operations:
 
         results = {}
 
-        for key, value in aggregatable_field_names.items():
+        for key in aggregatable_field_names.keys():
+            # key is aggregatable field, value is label
+            # e.g. key=category.keyword, value=category
             for bucket in response['aggregations'][key]['buckets']:
                 results[bucket['key']] = bucket['doc_count']
 
@@ -597,7 +559,7 @@ class Operations:
                 _source=field_names)
             # create post sort
             if sort_params is not None:
-                post_processing.append(self._sort_params_to_postprocessing(sort_params))
+                post_processing.append(SortFieldAction(sort_params))
 
         if is_scan:
             while True:
@@ -611,11 +573,6 @@ class Operations:
             df = self._apply_df_post_processing(df, post_processing)
             collector.collect(df)
 
-    def iloc(self, index, field_names):
-        # index and field_names are indexers
-        task = ('iloc', (index, field_names))
-        self._tasks.append(task)
-
     def index_count(self, query_compiler, field):
         # field is the index field so count values
         query_params, post_processing = self._resolve_tasks()
@@ -671,28 +628,16 @@ class Operations:
         # b not in ['a','b','c']
         # For now use term queries
         if field == Index.ID_INDEX_FIELD:
-            task = ('query_ids', ('must_not', items))
+            task = QueryIdsTask(False, items)
         else:
-            task = ('query_terms', ('must_not', (field, items)))
+            task = QueryTermsTask(False, field, items)
         self._tasks.append(task)
 
-    @staticmethod
-    def _sort_params_to_postprocessing(input):
-        # Split string
-        sort_params = input.split(":")
-
-        query_sort_field = sort_params[0]
-        query_sort_order = Operations.SortOrder.from_string(sort_params[1])
-
-        task = ('sort_field', (query_sort_field, query_sort_order))
-
-        return task
-
     @staticmethod
     def _query_params_to_size_and_sort(query_params):
         sort_params = None
         if query_params['query_sort_field'] and query_params['query_sort_order']:
-            sort_params = query_params['query_sort_field'] + ":" + Operations.SortOrder.to_string(
+            sort_params = query_params['query_sort_field'] + ":" + SortOrder.to_string(
                 query_params['query_sort_order'])
 
         size = query_params['query_size']
@@ -703,37 +648,16 @@ class Operations:
     def _count_post_processing(post_processing):
         size = None
         for action in post_processing:
-            if action[0] == 'head' or action[0] == 'tail':
-                if size is None or action[1][1] < size:
-                    size = action[1][1]
+            if isinstance(action, SizeTask):
+                if size is None or action.size() < size:
+                    size = action.size()
 
         return size
 
     @staticmethod
     def _apply_df_post_processing(df, post_processing):
         for action in post_processing:
-            if action == 'sort_index':
-                df = df.sort_index()
-            elif action[0] == 'head':
-                df = df.head(action[1][1])
-            elif action[0] == 'tail':
-                df = df.tail(action[1][1])
-            elif action[0] == 'sort_field':
-                sort_field = action[1][0]
-                sort_order = action[1][1]
-                if sort_order == Operations.SortOrder.ASC:
-                    df = df.sort_values(sort_field, True)
-                else:
-                    df = df.sort_values(sort_field, False)
-            elif action[0] == 'iloc':
-                index_indexer = action[1][0]
-                field_name_indexer = action[1][1]
-                if index_indexer is None:
-                    index_indexer = slice(None)
-                if field_name_indexer is None:
-                    field_name_indexer = slice(None)
-                df = df.iloc[index_indexer, field_name_indexer]
-            # field_names could be in here (and we ignore it)
+            df = action.resolve_action(df)
 
         return df
 
@@ -752,337 +676,7 @@ class Operations:
         post_processing = []
 
         for task in self._tasks:
-            if task[0] == 'head':
-                query_params, post_processing = self._resolve_head(task, query_params, post_processing)
-            elif task[0] == 'tail':
-                query_params, post_processing = self._resolve_tail(task, query_params, post_processing)
-            elif task[0] == 'iloc':
-                query_params, post_processing = self._resolve_iloc(task, query_params, post_processing)
-            elif task[0] == 'query_ids':
-                query_params, post_processing = self._resolve_query_ids(task, query_params, post_processing)
-            elif task[0] == 'query_terms':
-                query_params, post_processing = self._resolve_query_terms(task, query_params, post_processing)
-            elif task[0] == 'boolean_filter':
-                query_params, post_processing = self._resolve_boolean_filter(task, query_params, post_processing)
-            elif task[0] == 'arithmetic_op_fields':
-                query_params, post_processing = self._resolve_arithmetic_op_fields(task, query_params, post_processing)
-            else:  # a lot of operations simply post-process the dataframe - put these straight through
-                query_params, post_processing = self._resolve_post_processing_task(task, query_params, post_processing)
-
-        return query_params, post_processing
-
-    @staticmethod
-    def _resolve_head(item, query_params, post_processing):
-        # head - sort asc, size n
-        # |12345-------------|
-        query_sort_field = item[1][0]
-        query_sort_order = Operations.SortOrder.ASC
-        query_size = item[1][1]
-
-        # If we are already postprocessing the query results, we just get 'head' of these
-        # (note, currently we just append another head, we don't optimise by
-        # overwriting previous head)
-        if len(post_processing) > 0:
-            post_processing.append(item)
-            return query_params, post_processing
-
-        if query_params['query_sort_field'] is None:
-            query_params['query_sort_field'] = query_sort_field
-        # if it is already sorted we use existing field
-
-        if query_params['query_sort_order'] is None:
-            query_params['query_sort_order'] = query_sort_order
-        # if it is already sorted we get head of existing order
-
-        if query_params['query_size'] is None:
-            query_params['query_size'] = query_size
-        else:
-            # truncate if head is smaller
-            if query_size < query_params['query_size']:
-                query_params['query_size'] = query_size
-
-        return query_params, post_processing
-
-    @staticmethod
-    def _resolve_tail(item, query_params, post_processing):
-        # tail - sort desc, size n, post-process sort asc
-        # |-------------12345|
-        query_sort_field = item[1][0]
-        query_sort_order = Operations.SortOrder.DESC
-        query_size = item[1][1]
-
-        # If this is a tail of a tail adjust settings and return
-        if query_params['query_size'] is not None and \
-                query_params['query_sort_order'] == query_sort_order and \
-                post_processing == ['sort_index']:
-            if query_size < query_params['query_size']:
-                query_params['query_size'] = query_size
-            return query_params, post_processing
-
-        # If we are already postprocessing the query results, just get 'tail' of these
-        # (note, currently we just append another tail, we don't optimise by
-        # overwriting previous tail)
-        if len(post_processing) > 0:
-            post_processing.append(item)
-            return query_params, post_processing
-
-        # If results are already constrained, just get 'tail' of these
-        # (note, currently we just append another tail, we don't optimise by
-        # overwriting previous tail)
-        if query_params['query_size'] is not None:
-            post_processing.append(item)
-            return query_params, post_processing
-        else:
-            query_params['query_size'] = query_size
-        if query_params['query_sort_field'] is None:
-            query_params['query_sort_field'] = query_sort_field
-        if query_params['query_sort_order'] is None:
-            query_params['query_sort_order'] = query_sort_order
-        else:
-            # reverse sort order
-            query_params['query_sort_order'] = Operations.SortOrder.reverse(query_sort_order)
-
-        post_processing.append('sort_index')
-
-        return query_params, post_processing
-
-    @staticmethod
-    def _resolve_iloc(item, query_params, post_processing):
-        # tail - sort desc, size n, post-process sort asc
-        # |---4--7-9---------|
-
-        # This is a list of items we return via an integer index
-        int_index = item[1][0]
-        if int_index is not None:
-            last_item = int_index.max()
-
-            # If we have a query_size we do this post processing
-            if query_params['query_size'] is not None:
-                post_processing.append(item)
-                return query_params, post_processing
-
-            # size should be > last item
-            query_params['query_size'] = last_item + 1
-        post_processing.append(item)
-
-        return query_params, post_processing
-
-    @staticmethod
-    def _resolve_query_ids(item, query_params, post_processing):
-        # task = ('query_ids', ('must_not', items))
-        must_clause = item[1][0]
-        ids = item[1][1]
-
-        if must_clause == 'must':
-            query_params['query'].ids(ids, must=True)
-        else:
-            query_params['query'].ids(ids, must=False)
-
-        return query_params, post_processing
-
-    @staticmethod
-    def _resolve_query_terms(item, query_params, post_processing):
-        # task = ('query_terms', ('must_not', (field, terms)))
-        must_clause = item[1][0]
-        field = item[1][1][0]
-        terms = item[1][1][1]
-
-        if must_clause == 'must':
-            query_params['query'].terms(field, terms, must=True)
-        else:
-            query_params['query'].terms(field, terms, must=False)
-
-        return query_params, post_processing
-
-    @staticmethod
-    def _resolve_boolean_filter(item, query_params, post_processing):
-        # task = ('boolean_filter', object)
-        boolean_filter = item[1]
-
-        query_params['query'].update_boolean_filter(boolean_filter)
-
-        return query_params, post_processing
-
-    def _resolve_arithmetic_op_fields(self, item, query_params, post_processing):
-        # task = ('arithmetic_op_fields', (field_name, (op_name, (left_field, right_field))))
-        field_name = item[1][0]
-        op_name = item[1][1][0]
-        left_field = item[1][1][1][0]
-        right_field = item[1][1][1][1]
-
-        try:
-            op_type = item[2]
-        except IndexError:
-            op_type = None
-
-        # https://www.elastic.co/guide/en/elasticsearch/painless/current/painless-api-reference-shared-java-lang.html#painless-api-reference-shared-Math
-        if not op_type:
-            if isinstance(left_field, str) and isinstance(right_field, str):
-                """
-                (if op_name = '__truediv__')
-
-                "script_fields": {
-                    "field_name": {
-                    "script": {
-                        "source": "doc[left_field].value / doc[right_field].value"
-                    }
-                    }
-                }
-                """
-                if op_name == '__add__':
-                    source = "doc['{0}'].value + doc['{1}'].value".format(left_field, right_field)
-                elif op_name == '__truediv__':
-                    source = "doc['{0}'].value / doc['{1}'].value".format(left_field, right_field)
-                elif op_name == '__floordiv__':
-                    source = "Math.floor(doc['{0}'].value / doc['{1}'].value)".format(left_field, right_field)
-                elif op_name == '__pow__':
-                    source = "Math.pow(doc['{0}'].value, doc['{1}'].value)".format(left_field, right_field)
-                elif op_name == '__mod__':
-                    source = "doc['{0}'].value % doc['{1}'].value".format(left_field, right_field)
-                elif op_name == '__mul__':
-                    source = "doc['{0}'].value * doc['{1}'].value".format(left_field, right_field)
-                elif op_name == '__sub__':
-                    source = "doc['{0}'].value - doc['{1}'].value".format(left_field, right_field)
-                else:
-                    raise NotImplementedError("Not implemented operation '{0}'".format(op_name))
-
-                if query_params['query_script_fields'] is None:
-                    query_params['query_script_fields'] = {}
-                query_params['query_script_fields'][field_name] = {
-                    'script': {
-                        'source': source
-                    }
-                }
-            elif isinstance(left_field, str) and np.issubdtype(np.dtype(type(right_field)), np.number):
-                """
-                (if op_name = '__truediv__')
-
-                "script_fields": {
-                    "field_name": {
-                    "script": {
-                        "source": "doc[left_field].value / right_field"
-                    }
-                    }
-                }
-                """
-                if op_name == '__add__':
-                    source = "doc['{0}'].value + {1}".format(left_field, right_field)
-                elif op_name == '__truediv__':
-                    source = "doc['{0}'].value / {1}".format(left_field, right_field)
-                elif op_name == '__floordiv__':
-                    source = "Math.floor(doc['{0}'].value / {1})".format(left_field, right_field)
-                elif op_name == '__pow__':
-                    source = "Math.pow(doc['{0}'].value, {1})".format(left_field, right_field)
-                elif op_name == '__mod__':
-                    source = "doc['{0}'].value % {1}".format(left_field, right_field)
-                elif op_name == '__mul__':
-                    source = "doc['{0}'].value * {1}".format(left_field, right_field)
-                elif op_name == '__sub__':
-                    source = "doc['{0}'].value - {1}".format(left_field, right_field)
-                else:
-                    raise NotImplementedError("Not implemented operation '{0}'".format(op_name))
-            elif np.issubdtype(np.dtype(type(left_field)), np.number) and isinstance(right_field, str):
-                """
-                (if op_name = '__truediv__')
-
-                "script_fields": {
-                    "field_name": {
-                    "script": {
-                        "source": "left_field / doc['right_field'].value"
-                    }
-                    }
-                }
-                """
-                if op_name == '__add__':
-                    source = "{0} + doc['{1}'].value".format(left_field, right_field)
-                elif op_name == '__truediv__':
-                    source = "{0} / doc['{1}'].value".format(left_field, right_field)
-                elif op_name == '__floordiv__':
-                    source = "Math.floor({0} / doc['{1}'].value)".format(left_field, right_field)
-                elif op_name == '__pow__':
-                    source = "Math.pow({0}, doc['{1}'].value)".format(left_field, right_field)
-                elif op_name == '__mod__':
-                    source = "{0} % doc['{1}'].value".format(left_field, right_field)
-                elif op_name == '__mul__':
-                    source = "{0} * doc['{1}'].value".format(left_field, right_field)
-                elif op_name == '__sub__':
-                    source = "{0} - doc['{1}'].value".format(left_field, right_field)
-                else:
-                    raise NotImplementedError("Not implemented operation '{0}'".format(op_name))
-
-            else:
-                raise TypeError("Types for operation inconsistent {} {} {}", type(left_field), type(right_field), op_name)
-
-        elif op_type[0] == "string":
-            # we need to check the type of string addition
-            if op_type[1] == "s":
-                """
-                (if op_name = '__add__')
-
-                "script_fields": {
-                    "field_name": {
-                    "script": {
-                        "source": "doc[left_field].value + doc[right_field].value"
-                    }
-                    }
-                }
-                """
-                if op_name == '__add__':
-                    source = "doc['{0}'].value + doc['{1}'].value".format(left_field, right_field)
-                else:
-                    raise NotImplementedError("Not implemented operation '{0}'".format(op_name))
-
-            elif op_type[1] == "r":
-                if isinstance(left_field, str) and isinstance(right_field, str):
-                    """
-                    (if op_name = '__add__')
-
-                    "script_fields": {
-                        "field_name": {
-                        "script": {
-                            "source": "doc[left_field].value + right_field"
-                        }
-                        }
-                    }
-                    """
-                    if op_name == '__add__':
-                        source = "doc['{0}'].value + '{1}'".format(left_field, right_field)
-                    else:
-                        raise NotImplementedError("Not implemented operation '{0}'".format(op_name))
-
-            elif op_type[1] == 'l':
-                if isinstance(left_field, str) and isinstance(right_field, str):
-                    """
-                    (if op_name = '__add__')
-
-                    "script_fields": {
-                        "field_name": {
-                        "script": {
-                            "source": "left_field + doc[right_field].value"
-                        }
-                        }
-                    }
-                    """
-                    if op_name == '__add__':
-                        source = "'{0}' + doc['{1}'].value".format(left_field, right_field)
-                    else:
-                        raise NotImplementedError("Not implemented operation '{0}'".format(op_name))
-
-        if query_params['query_script_fields'] is None:
-            query_params['query_script_fields'] = {}
-        query_params['query_script_fields'][field_name] = {
-            'script': {
-                'source': source
-            }
-        }
-
-        return query_params, post_processing
-
-    @staticmethod
-    def _resolve_post_processing_task(item, query_params, post_processing):
-        # Just do this in post-processing
-        if item[0] != 'field_names':
-            post_processing.append(item)
+            query_params, post_processing = task.resolve_task(query_params, post_processing)
 
         return query_params, post_processing
 
@@ -1121,5 +715,5 @@ class Operations:
         buf.write(" post_processing: {0}\n".format(post_processing))
 
     def update_query(self, boolean_filter):
-        task = ('boolean_filter', boolean_filter)
+        task = BooleanFilterTask(boolean_filter)
         self._tasks.append(task)
diff --git a/eland/query_compiler.py b/eland/query_compiler.py
index b5bd00f..85361e0 100644
--- a/eland/query_compiler.py
+++ b/eland/query_compiler.py
@@ -461,6 +461,7 @@ class ElandQueryCompiler:
         self._index.info_es(buf)
         self._mappings.info_es(buf)
         self._operations.info_es(buf)
+        self._name_mapper.info_es(buf)
 
     def describe(self):
         return self._operations.describe(self)
@@ -548,7 +549,7 @@ class ElandQueryCompiler:
         else:
             raise ValueError(
                 "Can not perform arithmetic operations on non aggregatable fields"
-                "One of [{}, {}] is not aggregatable.".format(self.name, right.name)
+                "One of [{}, {}] is not aggregatable.".format(self_field, right_field)
         )
 
     def arithmetic_op_fields(self, new_field_name, op, left_field, right_field, op_type=None):
@@ -648,6 +649,9 @@ class ElandQueryCompiler:
                 display_to_field_names=self._display_to_field_names.copy()
             )
 
+        def info_es(self, buf):
+            buf.write("'field_to_display_names': {}\n".format(self._field_to_display_names))
+            buf.write("'display_to_field_names': {}\n".format(self._display_to_field_names))
 
 def elasticsearch_date_to_pandas_date(value: Union[int, str], date_format: str) -> pd.Timestamp:
     """
diff --git a/eland/series.py b/eland/series.py
index 7e1d7de..8caf6ad 100644
--- a/eland/series.py
+++ b/eland/series.py
@@ -215,7 +215,7 @@ class Series(NDFrame):
         Returns
         -------
         pandas.Series
-            number of occurences of each value in the column
+            number of occurrences of each value in the column
 
         See Also
         --------
diff --git a/eland/tasks.py b/eland/tasks.py
new file mode 100644
index 0000000..c939b02
--- /dev/null
+++ b/eland/tasks.py
@@ -0,0 +1,438 @@
+from abc import ABC, abstractmethod
+from enum import Enum
+
+import numpy as np
+
+from eland.actions import HeadAction, TailAction, SortIndexAction
+
+
+class SortOrder(Enum):
+    ASC = 0
+    DESC = 1
+
+    @staticmethod
+    def reverse(order):
+        if order == SortOrder.ASC:
+            return SortOrder.DESC
+
+        return SortOrder.ASC
+
+    @staticmethod
+    def to_string(order):
+        if order == SortOrder.ASC:
+            return "asc"
+
+        return "desc"
+
+    @staticmethod
+    def from_string(order):
+        if order == "asc":
+            return SortOrder.ASC
+
+        return SortOrder.DESC
+
+
+# -------------------------------------------------------------------------------------------------------------------- #
+# Tasks                                                                                                                #
+# -------------------------------------------------------------------------------------------------------------------- #
+class Task(ABC):
+    """
+    Abstract class for tasks
+
+    Parameters
+    ----------
+        task_type: str
+            The task type (e.g. head, tail etc.)
+    """
+
+    def __init__(self, task_type):
+        self._task_type = task_type
+
+    @property
+    def type(self):
+        return self._task_type
+
+    @abstractmethod
+    def resolve_task(self, query_params, post_processing):
+        pass
+
+    @abstractmethod
+    def __repr__(self):
+        pass
+
+
+class SizeTask(Task):
+    def __init__(self, task_type):
+        super().__init__(task_type)
+
+    @abstractmethod
+    def size(self):
+        # must override
+        pass
+
+
+class HeadTask(SizeTask):
+    def __init__(self, sort_field, count):
+        super().__init__("head")
+
+        # Add a task that is an ascending sort with size=count
+        self._sort_field = sort_field
+        self._count = count
+
+    def __repr__(self):
+        return "('{}': ('sort_field': '{}', 'count': {}))".format(self._task_type, self._sort_field, self._count)
+
+    def resolve_task(self, query_params, post_processing):
+        # head - sort asc, size n
+        # |12345-------------|
+        query_sort_field = self._sort_field
+        query_sort_order = SortOrder.ASC
+        query_size = self._count
+
+        # If we are already postprocessing the query results, we just get 'head' of these
+        # (note, currently we just append another head, we don't optimise by
+        # overwriting previous head)
+        if len(post_processing) > 0:
+            post_processing.append(HeadAction(self._count))
+            return query_params, post_processing
+
+        if query_params['query_sort_field'] is None:
+            query_params['query_sort_field'] = query_sort_field
+        # if it is already sorted we use existing field
+
+        if query_params['query_sort_order'] is None:
+            query_params['query_sort_order'] = query_sort_order
+        # if it is already sorted we get head of existing order
+
+        if query_params['query_size'] is None:
+            query_params['query_size'] = query_size
+        else:
+            # truncate if head is smaller
+            if query_size < query_params['query_size']:
+                query_params['query_size'] = query_size
+
+        return query_params, post_processing
+
+    def size(self):
+        return self._count
+
+
+class TailTask(SizeTask):
+    def __init__(self, sort_field, count):
+        super().__init__("tail")
+
+        # Add a task that is descending sort with size=count
+        self._sort_field = sort_field
+        self._count = count
+
+    def __repr__(self):
+        return "('{}': ('sort_field': '{}', 'count': {}))".format(self._task_type, self._sort_field, self._count)
+
+    def resolve_task(self, query_params, post_processing):
+        # tail - sort desc, size n, post-process sort asc
+        # |-------------12345|
+        query_sort_field = self._sort_field
+        query_sort_order = SortOrder.DESC
+        query_size = self._count
+
+        # If this is a tail of a tail adjust settings and return
+        if query_params['query_size'] is not None and \
+                query_params['query_sort_order'] == query_sort_order and \
+                post_processing == ['sort_index']:
+            if query_size < query_params['query_size']:
+                query_params['query_size'] = query_size
+            return query_params, post_processing
+
+        # If we are already postprocessing the query results, just get 'tail' of these
+        # (note, currently we just append another tail, we don't optimise by
+        # overwriting previous tail)
+        if len(post_processing) > 0:
+            post_processing.append(TailAction(self._count))
+            return query_params, post_processing
+
+        # If results are already constrained, just get 'tail' of these
+        # (note, currently we just append another tail, we don't optimise by
+        # overwriting previous tail)
+        if query_params['query_size'] is not None:
+            post_processing.append(TailAction(self._count))
+            return query_params, post_processing
+        else:
+            query_params['query_size'] = query_size
+        if query_params['query_sort_field'] is None:
+            query_params['query_sort_field'] = query_sort_field
+        if query_params['query_sort_order'] is None:
+            query_params['query_sort_order'] = query_sort_order
+        else:
+            # reverse sort order
+            query_params['query_sort_order'] = SortOrder.reverse(query_sort_order)
+
+        post_processing.append(SortIndexAction())
+
+        return query_params, post_processing
+
+    def size(self):
+        return self._count
+
+
+class QueryIdsTask(Task):
+    def __init__(self, must, ids):
+        """
+        Parameters
+        ----------
+        must: bool
+            Include or exclude these ids (must/must_not)
+
+        ids: list
+            ids for the filter
+        """
+        super().__init__("query_ids")
+
+        self._must = must
+        self._ids = ids
+
+    def resolve_task(self, query_params, post_processing):
+        query_params['query'].ids(self._ids, must=self._must)
+
+        return query_params, post_processing
+
+    def __repr__(self):
+        return "('{}': ('must': {}, 'ids': {}))".format(self._task_type, self._must, self._ids)
+
+
+class QueryTermsTask(Task):
+    def __init__(self, must, field, terms):
+        """
+        Parameters
+        ----------
+        must: bool
+            Include or exclude these ids (must/must_not)
+
+        field: str
+            field_name to filter
+
+        terms: list
+            field_values for filter
+        """
+        super().__init__("query_terms")
+
+        self._must = must
+        self._field = field
+        self._terms = terms
+
+    def __repr__(self):
+        return "('{}': ('must': {}, 'field': '{}', 'terms': {}))".format(self._task_type, self._must, self._field,
+                                                                         self._terms)
+
+    def resolve_task(self, query_params, post_processing):
+        query_params['query'].terms(self._field, self._terms, must=self._must)
+
+        return query_params, post_processing
+
+
+class BooleanFilterTask(Task):
+    def __init__(self, boolean_filter):
+        """
+        Parameters
+        ----------
+        boolean_filter: BooleanFilter or str
+            The filter to apply
+        """
+        super().__init__("boolean_filter")
+
+        self._boolean_filter = boolean_filter
+
+    def __repr__(self):
+        return "('{}': ('boolean_filter': {}))".format(self._task_type, repr(self._boolean_filter))
+
+    def resolve_task(self, query_params, post_processing):
+        query_params['query'].update_boolean_filter(self._boolean_filter)
+
+        return query_params, post_processing
+
+
+class ArithmeticOpFieldsTask(Task):
+    def __init__(self, field_name, op_name, left_field, right_field, op_type):
+        super().__init__("arithmetic_op_fields")
+
+        self._field_name = field_name
+        self._op_name = op_name
+        self._left_field = left_field
+        self._right_field = right_field
+        self._op_type = op_type
+
+    def __repr__(self):
+        return "('{}': (" \
+               "'field_name': {}, " \
+               "'op_name': {}, " \
+               "'left_field': {}, " \
+               "'right_field': {}, " \
+               "'op_type': {}" \
+               "))" \
+            .format(self._task_type, self._field_name, self._op_name, self._left_field, self._right_field,
+                    self._op_type)
+
+    def resolve_task(self, query_params, post_processing):
+        # https://www.elastic.co/guide/en/elasticsearch/painless/current/painless-api-reference-shared-java-lang.html#painless-api-reference-shared-Math
+        if not self._op_type:
+            if isinstance(self._left_field, str) and isinstance(self._right_field, str):
+                """
+                (if op_name = '__truediv__')
+
+                "script_fields": {
+                    "field_name": {
+                    "script": {
+                        "source": "doc[left_field].value / doc[right_field].value"
+                    }
+                    }
+                }
+                """
+                if self._op_name == '__add__':
+                    source = "doc['{0}'].value + doc['{1}'].value".format(self._left_field, self._right_field)
+                elif self._op_name == '__truediv__':
+                    source = "doc['{0}'].value / doc['{1}'].value".format(self._left_field, self._right_field)
+                elif self._op_name == '__floordiv__':
+                    source = "Math.floor(doc['{0}'].value / doc['{1}'].value)".format(self._left_field,
+                                                                                      self._right_field)
+                elif self._op_name == '__pow__':
+                    source = "Math.pow(doc['{0}'].value, doc['{1}'].value)".format(self._left_field, self._right_field)
+                elif self._op_name == '__mod__':
+                    source = "doc['{0}'].value % doc['{1}'].value".format(self._left_field, self._right_field)
+                elif self._op_name == '__mul__':
+                    source = "doc['{0}'].value * doc['{1}'].value".format(self._left_field, self._right_field)
+                elif self._op_name == '__sub__':
+                    source = "doc['{0}'].value - doc['{1}'].value".format(self._left_field, self._right_field)
+                else:
+                    raise NotImplementedError("Not implemented operation '{0}'".format(self._op_name))
+
+                if query_params['query_script_fields'] is None:
+                    query_params['query_script_fields'] = {}
+                query_params['query_script_fields'][self._field_name] = {
+                    'script': {
+                        'source': source
+                    }
+                }
+            elif isinstance(self._left_field, str) and np.issubdtype(np.dtype(type(self._right_field)), np.number):
+                """
+                (if self._op_name = '__truediv__')
+
+                "script_fields": {
+                    "field_name": {
+                    "script": {
+                        "source": "doc[self._left_field].value / self._right_field"
+                    }
+                    }
+                }
+                """
+                if self._op_name == '__add__':
+                    source = "doc['{0}'].value + {1}".format(self._left_field, self._right_field)
+                elif self._op_name == '__truediv__':
+                    source = "doc['{0}'].value / {1}".format(self._left_field, self._right_field)
+                elif self._op_name == '__floordiv__':
+                    source = "Math.floor(doc['{0}'].value / {1})".format(self._left_field, self._right_field)
+                elif self._op_name == '__pow__':
+                    source = "Math.pow(doc['{0}'].value, {1})".format(self._left_field, self._right_field)
+                elif self._op_name == '__mod__':
+                    source = "doc['{0}'].value % {1}".format(self._left_field, self._right_field)
+                elif self._op_name == '__mul__':
+                    source = "doc['{0}'].value * {1}".format(self._left_field, self._right_field)
+                elif self._op_name == '__sub__':
+                    source = "doc['{0}'].value - {1}".format(self._left_field, self._right_field)
+                else:
+                    raise NotImplementedError("Not implemented operation '{0}'".format(self._op_name))
+            elif np.issubdtype(np.dtype(type(self._left_field)), np.number) and isinstance(self._right_field, str):
+                """
+                (if self._op_name = '__truediv__')
+
+                "script_fields": {
+                    "field_name": {
+                    "script": {
+                        "source": "self._left_field / doc['self._right_field'].value"
+                    }
+                    }
+                }
+                """
+                if self._op_name == '__add__':
+                    source = "{0} + doc['{1}'].value".format(self._left_field, self._right_field)
+                elif self._op_name == '__truediv__':
+                    source = "{0} / doc['{1}'].value".format(self._left_field, self._right_field)
+                elif self._op_name == '__floordiv__':
+                    source = "Math.floor({0} / doc['{1}'].value)".format(self._left_field, self._right_field)
+                elif self._op_name == '__pow__':
+                    source = "Math.pow({0}, doc['{1}'].value)".format(self._left_field, self._right_field)
+                elif self._op_name == '__mod__':
+                    source = "{0} % doc['{1}'].value".format(self._left_field, self._right_field)
+                elif self._op_name == '__mul__':
+                    source = "{0} * doc['{1}'].value".format(self._left_field, self._right_field)
+                elif self._op_name == '__sub__':
+                    source = "{0} - doc['{1}'].value".format(self._left_field, self._right_field)
+                else:
+                    raise NotImplementedError("Not implemented operation '{0}'".format(self._op_name))
+
+            else:
+                raise TypeError("Types for operation inconsistent {} {} {}", type(self._left_field),
+                                type(self._right_field), self._op_name)
+
+        elif self._op_type[0] == "string":
+            # we need to check the type of string addition
+            if self._op_type[1] == "s":
+                """
+                (if self._op_name = '__add__')
+
+                "script_fields": {
+                    "field_name": {
+                    "script": {
+                        "source": "doc[self._left_field].value + doc[self._right_field].value"
+                    }
+                    }
+                }
+                """
+                if self._op_name == '__add__':
+                    source = "doc['{0}'].value + doc['{1}'].value".format(self._left_field, self._right_field)
+                else:
+                    raise NotImplementedError("Not implemented operation '{0}'".format(self._op_name))
+
+            elif self._op_type[1] == "r":
+                if isinstance(self._left_field, str) and isinstance(self._right_field, str):
+                    """
+                    (if self._op_name = '__add__')
+
+                    "script_fields": {
+                        "field_name": {
+                        "script": {
+                            "source": "doc[self._left_field].value + self._right_field"
+                        }
+                        }
+                    }
+                    """
+                    if self._op_name == '__add__':
+                        source = "doc['{0}'].value + '{1}'".format(self._left_field, self._right_field)
+                    else:
+                        raise NotImplementedError("Not implemented operation '{0}'".format(self._op_name))
+
+            elif self._op_type[1] == 'l':
+                if isinstance(self._left_field, str) and isinstance(self._right_field, str):
+                    """
+                    (if self._op_name = '__add__')
+
+                    "script_fields": {
+                        "field_name": {
+                        "script": {
+                            "source": "self._left_field + doc[self._right_field].value"
+                        }
+                        }
+                    }
+                    """
+                    if self._op_name == '__add__':
+                        source = "'{0}' + doc['{1}'].value".format(self._left_field, self._right_field)
+                    else:
+                        raise NotImplementedError("Not implemented operation '{0}'".format(self._op_name))
+
+        if query_params['query_script_fields'] is None:
+            query_params['query_script_fields'] = {}
+        query_params['query_script_fields'][self._field_name] = {
+            'script': {
+                'source': source
+            }
+        }
+
+        return query_params, post_processing
diff --git a/eland/tests/dataframe/test_aggs_pytest.py b/eland/tests/dataframe/test_aggs_pytest.py
index 0086515..a118079 100644
--- a/eland/tests/dataframe/test_aggs_pytest.py
+++ b/eland/tests/dataframe/test_aggs_pytest.py
@@ -27,3 +27,23 @@ class TestDataFrameAggs(TestData):
         print(ed_sum_min_std.dtypes)
 
         assert_almost_equal(pd_sum_min_std, ed_sum_min_std, check_less_precise=True)
+
+    def test_terms_aggs(self):
+        pd_flights = self.pd_flights()
+        ed_flights = self.ed_flights()
+
+        pd_sum_min = pd_flights.select_dtypes(include=[np.number]).agg(['sum', 'min'])
+        ed_sum_min = ed_flights.select_dtypes(include=[np.number]).agg(['sum', 'min'])
+
+        # Eland returns all float values for all metric aggs, pandas can return int
+        # TODO - investigate this more
+        pd_sum_min = pd_sum_min.astype('float64')
+        assert_almost_equal(pd_sum_min, ed_sum_min)
+
+        pd_sum_min_std = pd_flights.select_dtypes(include=[np.number]).agg(['sum', 'min', 'std'])
+        ed_sum_min_std = ed_flights.select_dtypes(include=[np.number]).agg(['sum', 'min', 'std'])
+
+        print(pd_sum_min_std.dtypes)
+        print(ed_sum_min_std.dtypes)
+
+        assert_almost_equal(pd_sum_min_std, ed_sum_min_std, check_less_precise=True)
diff --git a/eland/tests/dataframe/test_head_tail_pytest.py b/eland/tests/dataframe/test_head_tail_pytest.py
index f342ac2..0860382 100644
--- a/eland/tests/dataframe/test_head_tail_pytest.py
+++ b/eland/tests/dataframe/test_head_tail_pytest.py
@@ -85,3 +85,10 @@ class TestDataFrameHeadTail(TestData):
         ed_head_0 = ed_flights.head(0)
         pd_head_0 = pd_flights.head(0)
         assert_pandas_eland_frame_equal(pd_head_0, ed_head_0)
+
+    def test_doc_test_tail(self):
+        df = self.ed_flights()
+        df = df[(df.OriginAirportID == 'AMS') & (df.FlightDelayMin > 60)]
+        df = df[['timestamp', 'OriginAirportID', 'DestAirportID', 'FlightDelayMin']]
+        df = df.tail()
+        print(df)
diff --git a/eland/tests/series/test_str_arithmetics_pytest.py b/eland/tests/series/test_str_arithmetics_pytest.py
index d5b8341..67769b2 100644
--- a/eland/tests/series/test_str_arithmetics_pytest.py
+++ b/eland/tests/series/test_str_arithmetics_pytest.py
@@ -20,8 +20,7 @@ class TestSeriesArithmetics(TestData):
         with pytest.raises(TypeError):
             assert self.ed_ecommerce()['total_quantity'] + self.ed_ecommerce()['currency']
 
-    def test_str_add_ser(self):
-
+    def test_ser_add_ser(self):
         edadd = self.ed_ecommerce()['customer_first_name'] + self.ed_ecommerce()['customer_last_name']
         pdadd = self.pd_ecommerce()['customer_first_name'] + self.pd_ecommerce()['customer_last_name']
 
@@ -33,12 +32,31 @@ class TestSeriesArithmetics(TestData):
 
         assert_pandas_eland_series_equal(pdadd, edadd)
 
-    def test_ser_add_ser(self):
+    def test_str_add_ser(self):
         edadd = "The last name is: " + self.ed_ecommerce()['customer_last_name']
         pdadd = "The last name is: " + self.pd_ecommerce()['customer_last_name']
 
         assert_pandas_eland_series_equal(pdadd, edadd)
 
+    def test_bad_str_add_ser(self):
+        # TODO encode special characters better
+        #      Elasticsearch accepts this, but it will cause problems
+        edadd = " *" + self.ed_ecommerce()['customer_last_name']
+        pdadd = " *" + self.pd_ecommerce()['customer_last_name']
+
+        assert_pandas_eland_series_equal(pdadd, edadd)
+
+
+    def test_ser_add_str_add_ser(self):
+        pdadd = self.pd_ecommerce()['customer_first_name'] + self.pd_ecommerce()['customer_last_name']
+        print(pdadd.name)
+        edadd = self.ed_ecommerce()['customer_first_name'] + self.ed_ecommerce()['customer_last_name']
+        print(edadd.name)
+
+        print(edadd.info_es())
+
+        assert_pandas_eland_series_equal(pdadd, edadd)
+
     def test_non_aggregatable_add_str(self):
         with pytest.raises(ValueError):
             assert self.ed_ecommerce()['customer_gender'] + "is the gender"
diff --git a/eland/tests/series/test_value_counts_pytest.py b/eland/tests/series/test_value_counts_pytest.py
index 97effbf..a43d8a8 100644
--- a/eland/tests/series/test_value_counts_pytest.py
+++ b/eland/tests/series/test_value_counts_pytest.py
@@ -47,6 +47,14 @@ class TestSeriesValueCounts(TestData):
             assert ed_s.value_counts(es_size=-9)
 
     def test_value_counts_non_aggregatable(self):
+        ed_s = self.ed_ecommerce()['customer_first_name']
+        pd_s = self.pd_ecommerce()['customer_first_name']
+
+        pd_vc = pd_s.value_counts().head(20).sort_index()
+        ed_vc = ed_s.value_counts(es_size=20).sort_index()
+
+        assert_series_equal(pd_vc, ed_vc)
+
         ed_s = self.ed_ecommerce()['customer_gender']
         with pytest.raises(ValueError):
             assert ed_s.value_counts()