diff --git a/onnxconverter_common/__init__.py b/onnxconverter_common/__init__.py
index 26976ee..1d8da6e 100644
--- a/onnxconverter_common/__init__.py
+++ b/onnxconverter_common/__init__.py
@@ -1,8 +1,7 @@
-# -------------------------------------------------------------------------
 # Copyright (c) Microsoft Corporation. All rights reserved.
 # Licensed under the MIT License. See License.txt in the project root for
 # license information.
-# --------------------------------------------------------------------------
+###############################################################################
 
 """
 The entry point to onnxconverter-common.
diff --git a/onnxconverter_common/case_insensitive_dict.py b/onnxconverter_common/case_insensitive_dict.py
index f1706c9..41972d4 100644
--- a/onnxconverter_common/case_insensitive_dict.py
+++ b/onnxconverter_common/case_insensitive_dict.py
@@ -1,3 +1,8 @@
+# Copyright (c) Microsoft Corporation. All rights reserved.
+# Licensed under the MIT License. See License.txt in the project root for
+# license information.
+###############################################################################
+
 try:
     from collections.abc import Mapping, MutableMapping
 except ImportError:
diff --git a/onnxconverter_common/container.py b/onnxconverter_common/container.py
index 9036895..9d51675 100644
--- a/onnxconverter_common/container.py
+++ b/onnxconverter_common/container.py
@@ -1,8 +1,7 @@
-# -------------------------------------------------------------------------
 # Copyright (c) Microsoft Corporation. All rights reserved.
 # Licensed under the MIT License. See License.txt in the project root for
 # license information.
-# --------------------------------------------------------------------------
+###############################################################################
 
 import six
 from onnx import helper
diff --git a/onnxconverter_common/data_types.py b/onnxconverter_common/data_types.py
index b41efd5..91fbe20 100644
--- a/onnxconverter_common/data_types.py
+++ b/onnxconverter_common/data_types.py
@@ -1,8 +1,7 @@
-# -------------------------------------------------------------------------
 # Copyright (c) Microsoft Corporation. All rights reserved.
 # Licensed under the MIT License. See License.txt in the project root for
 # license information.
-# --------------------------------------------------------------------------
+###############################################################################
 
 import numbers
 import onnx
diff --git a/onnxconverter_common/decast.py b/onnxconverter_common/decast.py
index 2cff08e..e6ba720 100644
--- a/onnxconverter_common/decast.py
+++ b/onnxconverter_common/decast.py
@@ -1,10 +1,13 @@
+# Copyright (c) Microsoft Corporation. All rights reserved.
+# Licensed under the MIT License. See License.txt in the project root for
+# license information.
+###############################################################################
 import sys
 import onnx
 from .optimizer import LinkedNode, Solution
 
 
 def remove_cast(lnodes, op_set):
-
     while True:
         sln = []
         for n_ in lnodes:
diff --git a/onnxconverter_common/float16.py b/onnxconverter_common/float16.py
index e7b68a5..e09a779 100644
--- a/onnxconverter_common/float16.py
+++ b/onnxconverter_common/float16.py
@@ -1,4 +1,3 @@
-###########################################################################
 # Copyright (c) Microsoft Corporation. All rights reserved.
 # Licensed under the MIT License. See License.txt in the project root for
 # license information.
diff --git a/onnxconverter_common/interface.py b/onnxconverter_common/interface.py
index 8ac076f..306e2fe 100644
--- a/onnxconverter_common/interface.py
+++ b/onnxconverter_common/interface.py
@@ -1,8 +1,7 @@
-# -------------------------------------------------------------------------
 # Copyright (c) Microsoft Corporation. All rights reserved.
 # Licensed under the MIT License. See License.txt in the project root for
 # license information.
-# --------------------------------------------------------------------------
+###############################################################################
 # This file defines the interface of the converter internal object for callback,
 # So the usage of the methods and properties list here will not be affected among the different versions.
 
diff --git a/onnxconverter_common/metadata_props.py b/onnxconverter_common/metadata_props.py
index 816b2c8..9d57168 100644
--- a/onnxconverter_common/metadata_props.py
+++ b/onnxconverter_common/metadata_props.py
@@ -1,3 +1,8 @@
+# Copyright (c) Microsoft Corporation. All rights reserved.
+# Licensed under the MIT License. See License.txt in the project root for
+# license information.
+###############################################################################
+
 import warnings
 from .case_insensitive_dict import CaseInsensitiveDict
 from onnx import onnx_pb as onnx_proto
diff --git a/onnxconverter_common/onnx_ops.py b/onnxconverter_common/onnx_ops.py
index bab150b..df8437e 100644
--- a/onnxconverter_common/onnx_ops.py
+++ b/onnxconverter_common/onnx_ops.py
@@ -1,8 +1,8 @@
-# -------------------------------------------------------------------------
 # Copyright (c) Microsoft Corporation. All rights reserved.
 # Licensed under the MIT License. See License.txt in the project root for
 # license information.
-# --------------------------------------------------------------------------
+###############################################################################
+
 # This file contains some high-level APIs for applying operations on variables specified by names. We should try our
 # best to use those functions because they can produce ONNX operators according to the ONNX version specified in the
 # `container` argument. Notice that those function behaviors are defined in a way very similar to ONNX-1.2.
diff --git a/onnxconverter_common/oopb.py b/onnxconverter_common/oopb.py
new file mode 100644
index 0000000..33d0c36
--- /dev/null
+++ b/onnxconverter_common/oopb.py
@@ -0,0 +1,130 @@
+# coding=utf-8
+# Copyright (c) Microsoft Corporation. All rights reserved.
+# Licensed under the MIT License. See License.txt in the project root for
+# license information.
+###############################################################################
+
+import functools
+import numpy as np
+from onnx import onnx_pb as onnx_proto
+from onnx.mapping import NP_TYPE_TO_TENSOR_TYPE
+from . import onnx_ops
+
+
+class _OperatorNameContext:
+    def __init__(self, oopb, basename):
+        self.basename = basename
+        self.oopb = oopb
+
+    def __enter__(self):
+        assert self.oopb.basename is None, "The previous context doesn't quit"
+        self.oopb.basename = self.basename
+        return self.oopb
+
+    def __exit__(self, type, value, traceback):
+        self.oopb.basename = None
+
+
+class OnnxOperatorBuilder:
+    def __init__(self, container, scope):
+        self._container = container
+        self._scope = scope
+        self.basename = None
+        self.int32 = onnx_proto.TensorProto.INT32
+        self.int64 = onnx_proto.TensorProto.INT64
+        self.float = onnx_proto.TensorProto.FLOAT
+        self.float16 = onnx_proto.TensorProto.FLOAT16
+        self.double = onnx_proto.TensorProto.DOUBLE
+        self.bool = onnx_proto.TensorProto.BOOL
+
+        apply_operations = onnx_ops.__dict__
+        for k_, m_ in apply_operations.items():
+            if k_.startswith("apply_") and callable(m_):
+                setattr(self, k_, functools.partial(self.apply_op, m_))
+
+    def as_default(self, basename):
+        return _OperatorNameContext(self, basename)
+
+    def _process_inputs(self, inputs, name):
+        if not isinstance(inputs, (list, tuple)):
+            inputs = [inputs]
+        ox_inputs = []
+        for i_ in inputs:
+            ox_n = i_
+            if isinstance(i_, np.ndarray):
+                ox_n = self._scope.get_unique_variable_name(name + '_i')
+                self._container.add_initializer(
+                    ox_n,
+                    NP_TYPE_TO_TENSOR_TYPE[i_.dtype],
+                    i_.shape,
+                    i_.flatten()
+                )
+            elif isinstance(i_, (tuple, list)):
+                ox_n = self._scope.get_unique_variable_name(name + i_[0])
+                self._container.add_initializer(
+                    ox_n,
+                    i_[1],
+                    i_[2].shape,
+                    i_[2].flatten()
+                )
+            elif isinstance(ox_n, str):
+                pass
+            else:
+                raise ValueError('Unknown type for ONNX initializer: {}'.format(type(ox_n)))
+            ox_inputs.append(ox_n)
+
+        return ox_inputs
+
+    def _generate_name(self, type_or_func, name):
+        base_name = (self.basename if self.basename else '') + '_'
+        if name is not None:
+            long_name = base_name + name
+        else:
+            if isinstance(type_or_func, str):
+                suffix = type_or_func.lower()
+            else:
+                suffix = type_or_func.__name__[len('apply_'):]
+            long_name = base_name + suffix
+        return long_name
+
+    def add_node(self, op_type, inputs, name=None, outputs=None, op_domain='', op_version=None, **attrs):
+        if op_version is None:
+            op_version = self._container.target_opset
+        name = self._generate_name(op_type, name)
+        if outputs is None:
+            ox_output = 1
+        else:
+            ox_output = outputs
+        if isinstance(ox_output, int):
+            ox_output = [self._scope.get_unique_variable_name(name + str(i_)) for i_ in range(ox_output)]
+        elif isinstance(ox_output, (list, tuple)):
+            pass
+        else:
+            raise ValueError('Unknown type for outputs: {}'.format(type(ox_output)))
+        ox_inputs = self._process_inputs(inputs, name)
+        self._container.add_node(op_type, ox_inputs, ox_output, op_domain, op_version,
+                                 name=self._scope.get_unique_operator_name(name), **attrs)
+        return ox_output[0] if outputs is None else ox_output
+
+    def apply_op(self, apply_func, inputs, name=None, outputs=None, **attrs):
+        name = self._generate_name(apply_func, name)
+        if outputs is None:
+            ox_output = 1
+        else:
+            ox_output = outputs
+        if isinstance(ox_output, int):
+            ox_output = [self._scope.get_unique_variable_name(name + str(i_)) for i_ in range(ox_output)]
+        elif isinstance(ox_output, (list, tuple)):
+            pass
+        else:
+            raise ValueError('Unknown type for outputs: {}'.format(type(ox_output)))
+        ox_inputs = self._process_inputs(inputs, name)
+        apply_func(self._scope, ox_inputs, ox_output, self._container,
+                   operator_name=self._scope.get_unique_operator_name(name), **attrs)
+        return ox_output[0] if outputs is None else ox_output
+
+    def apply_op_name(self, apply_func_name, inputs, name=None, outputs=None, **attrs):
+        apply_operations = onnx_ops.__dict__
+        apply_func = apply_operations[apply_func_name]
+        assert apply_func is not None, "{} not implemented in onnx_ops.py.".format(apply_func_name)
+        return self.apply_op(apply_func, inputs, name, outputs)
diff --git a/onnxconverter_common/optimizer.py b/onnxconverter_common/optimizer.py
index b939531..bb0433d 100644
--- a/onnxconverter_common/optimizer.py
+++ b/onnxconverter_common/optimizer.py
@@ -1,8 +1,8 @@
-# -------------------------------------------------------------------------
 # Copyright (c) Microsoft Corporation. All rights reserved.
 # Licensed under the MIT License. See License.txt in the project root for
 # license information.
-# --------------------------------------------------------------------------
+###############################################################################
+
 import six
 import numpy as np
 import onnx
diff --git a/onnxconverter_common/registration.py b/onnxconverter_common/registration.py
index 2b14831..8d44698 100644
--- a/onnxconverter_common/registration.py
+++ b/onnxconverter_common/registration.py
@@ -1,8 +1,7 @@
-# -------------------------------------------------------------------------
 # Copyright (c) Microsoft Corporation. All rights reserved.
 # Licensed under the MIT License. See License.txt in the project root for
 # license information.
-# --------------------------------------------------------------------------
+###############################################################################
 
 # This dictionary defines the converters which can be invoked in the conversion framework defined in topology.py. A key
 # in this dictionary is an operator's unique ID (e.g., string and type) while the associated value is the callable
diff --git a/onnxconverter_common/shape_calculator.py b/onnxconverter_common/shape_calculator.py
index 195f7ec..0932817 100644
--- a/onnxconverter_common/shape_calculator.py
+++ b/onnxconverter_common/shape_calculator.py
@@ -1,11 +1,12 @@
-# -------------------------------------------------------------------------
 # Copyright (c) Microsoft Corporation. All rights reserved.
 # Licensed under the MIT License. See License.txt in the project root for
 # license information.
-# --------------------------------------------------------------------------
+###############################################################################
+
 """
 Common functions to convert any learner based on trees.
 """
+
 import numpy as np
 import numbers
 import six
diff --git a/onnxconverter_common/topology.py b/onnxconverter_common/topology.py
index ecb03d8..c03975d 100644
--- a/onnxconverter_common/topology.py
+++ b/onnxconverter_common/topology.py
@@ -1,15 +1,13 @@
-# -------------------------------------------------------------------------
+# coding=utf-8
 # Copyright (c) Microsoft Corporation. All rights reserved.
 # Licensed under the MIT License. See License.txt in the project root for
 # license information.
-# --------------------------------------------------------------------------
+###############################################################################
 
 import re
 import warnings
 from logging import getLogger
 from distutils.version import StrictVersion
-import onnx
-from onnx import onnx_pb as onnx_proto
 from onnx import helper
 from .metadata_props import add_metadata_props
 from . import registration
@@ -17,7 +15,7 @@
 from .data_types import *
 from .container import ModelComponentContainer
 from .optimizer import optimize_onnx
-from .interface import OperatorBase
+from .interface import OperatorBase, ScopeBase
 
 
 class Variable:
@@ -110,7 +108,7 @@ def infer_types(self):
         registration.get_shape_calculator(self.type)(self)
 
 
-class Scope:
+class Scope(ScopeBase):
 
     def __init__(self, name, parent_scopes=None, variable_name_set=None, operator_name_set=None, target_opset=None):
         '''
@@ -786,7 +784,7 @@ def convert_topology(topology, model_name, doc_string, target_opset, targeted_on
         i += 1
         if container.target_opset < op_version:
             raise RuntimeError(('The specified opset %d is too low to convert this model, ' +
-                               'which requires at least opset %d.') % (container.target_opset, op_version))
+                                'which requires at least opset %d.') % (container.target_opset, op_version))
         elif container.target_opset > op_version:
             getLogger('onnxmltools').warning('The maximum opset needed by this model is only %d.' % op_version)
 
diff --git a/onnxconverter_common/tree_ensemble.py b/onnxconverter_common/tree_ensemble.py
index d5487f4..e185e29 100644
--- a/onnxconverter_common/tree_ensemble.py
+++ b/onnxconverter_common/tree_ensemble.py
@@ -1,11 +1,12 @@
-# -------------------------------------------------------------------------
 # Copyright (c) Microsoft Corporation. All rights reserved.
 # Licensed under the MIT License. See License.txt in the project root for
 # license information.
-# --------------------------------------------------------------------------
+###############################################################################
+
 """
 Common functions to convert any learner based on trees.
 """
+
 from .registration import register_converter
 
 
diff --git a/onnxconverter_common/utils.py b/onnxconverter_common/utils.py
index 62f6d7b..c2b7f88 100644
--- a/onnxconverter_common/utils.py
+++ b/onnxconverter_common/utils.py
@@ -1,13 +1,12 @@
-# -------------------------------------------------------------------------
 # Copyright (c) Microsoft Corporation. All rights reserved.
 # Licensed under the MIT License. See License.txt in the project root for
 # license information.
-# --------------------------------------------------------------------------
+###############################################################################
 
 import numbers, six
 import numpy as np
 import warnings
-from distutils.version import LooseVersion, StrictVersion
+from distutils.version import LooseVersion
 
 
 def sparkml_installed():
@@ -20,6 +19,7 @@ def sparkml_installed():
     except ImportError:
         return False
 
+
 def sklearn_installed():
     """
     Checks that *scikit-learn* is available.
@@ -30,6 +30,7 @@ def sklearn_installed():
     except ImportError:
         return False
 
+
 def skl2onnx_installed():
     """
     Checks that *skl2onnx* converter is available.
@@ -40,6 +41,7 @@ def skl2onnx_installed():
     except ImportError:
         return False
 
+
 def coreml_installed():
     """
     Checks that *coremltools* is available.
@@ -140,6 +142,7 @@ def xgboost_installed():
         warnings.warn('The converter works for xgboost >= 0.7. Earlier versions might not.')
     return True
 
+
 def h2o_installed():
     """
     Checks that *h2o* is available.
@@ -150,6 +153,7 @@ def h2o_installed():
         return False
     return True
 
+
 def get_producer():
     """
     Internal helper function to return the producer
@@ -203,7 +207,7 @@ def is_string_type(item):
     if isinstance(item, np.ndarray):
         return np.issubdtype(item.dtype, np.str_)
     return isinstance(item, types)
-    
+
 
 def cast_list(type, items):
     return [type(item) for item in items]
diff --git a/tests/test_oopb.py b/tests/test_oopb.py
new file mode 100644
index 0000000..94904a2
--- /dev/null
+++ b/tests/test_oopb.py
@@ -0,0 +1,45 @@
+import unittest
+import numpy as np
+from onnxconverter_common.oopb import OnnxOperatorBuilder
+from onnxconverter_common.container import ModelComponentContainer, RawModelContainer
+from onnxconverter_common.topology import Topology, convert_topology
+
+
+class _SimpleRawModelContainer(RawModelContainer):
+    def __init__(self):
+        super(_SimpleRawModelContainer, self).__init__(None)
+
+    @property
+    def input_names(self):
+        return ['input_0', 'input_1']
+
+    @property
+    def output_names(self):
+        return ['m_output']
+
+
+class OnnxOpTestCase(unittest.TestCase):
+    def setUp(self):
+        self.raw_model = _SimpleRawModelContainer()
+
+    def test_apply_op(self):
+        topo = Topology(self.raw_model)
+        scope = topo.declare_scope('__ROOT__')
+        container = ModelComponentContainer(target_opset=7)
+
+        with OnnxOperatorBuilder(container, scope).as_default('node_bn') as oopb:
+            mul_node = oopb.apply_mul(self.raw_model.input_names)
+            sub_node = oopb.apply_sub([mul_node] + [np.array([1.0, 2.0])])
+            output = oopb.add_node('Add',
+                                   [sub_node, ('add_1', oopb.float, np.array([3.0, 4.0]))],
+                                   outputs=self.raw_model.output_names)
+
+        self.assertIsInstance(output, list)
+        self.assertEqual(len(container.nodes), 3)
+        self.assertEqual(len(container.initializers), 2)
+        self.assertTrue(container.nodes[0].name.startswith('node_bn'))
+
+        # a fake conversion to check the scope data correctness.
+        oxml = convert_topology(topo, 'test', "doc_string", 7, None)
+        self.assertIsNotNone(oxml)
+        self.assertEqual(len(oxml.graph.node), 0)