diff --git a/taskflow/blocks/__init__.py b/taskflow/blocks/__init__.py
new file mode 100644
index 00000000..8f523a6a
--- /dev/null
+++ b/taskflow/blocks/__init__.py
@@ -0,0 +1,31 @@
+# -*- coding: utf-8 -*-
+
+# vim: tabstop=4 shiftwidth=4 softtabstop=4
+
+#    Copyright (C) 2012-2013 Yahoo! Inc. All Rights Reserved.
+#
+#    Licensed under the Apache License, Version 2.0 (the "License"); you may
+#    not use this file except in compliance with the License. You may obtain
+#    a copy of the License at
+#
+#         http://www.apache.org/licenses/LICENSE-2.0
+#
+#    Unless required by applicable law or agreed to in writing, software
+#    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+#    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+#    License for the specific language governing permissions and limitations
+#    under the License.
+
+"""Blocks define *structure*
+
+There are two categories of blocks:
+- patterns, which provide convenient way to express basic flow
+  structure, like linear flow or parallel flow
+- terminals, which run task or needed for housekeeping
+
+"""
+
+# Import most used blocks into this module namespace:
+from taskflow.blocks.patterns import LinearFlow    # noqa
+from taskflow.blocks.patterns import ParallelFlow  # noqa
+from taskflow.blocks.task import Task              # noqa
diff --git a/taskflow/blocks/base.py b/taskflow/blocks/base.py
new file mode 100644
index 00000000..1620546c
--- /dev/null
+++ b/taskflow/blocks/base.py
@@ -0,0 +1,25 @@
+
+# -*- coding: utf-8 -*-
+
+# vim: tabstop=4 shiftwidth=4 softtabstop=4
+
+#    Copyright (C) 2012-2013 Yahoo! Inc. All Rights Reserved.
+#
+#    Licensed under the Apache License, Version 2.0 (the "License"); you may
+#    not use this file except in compliance with the License. You may obtain
+#    a copy of the License at
+#
+#         http://www.apache.org/licenses/LICENSE-2.0
+#
+#    Unless required by applicable law or agreed to in writing, software
+#    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+#    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+#    License for the specific language governing permissions and limitations
+#    under the License.
+
+
+class Block(object):
+    """Basic flow structure unit
+
+    From blocks the flow definition is build.
+    """
diff --git a/taskflow/blocks/patterns.py b/taskflow/blocks/patterns.py
new file mode 100644
index 00000000..1bbfcc58
--- /dev/null
+++ b/taskflow/blocks/patterns.py
@@ -0,0 +1,57 @@
+
+# -*- coding: utf-8 -*-
+
+# vim: tabstop=4 shiftwidth=4 softtabstop=4
+
+#    Copyright (C) 2012-2013 Yahoo! Inc. All Rights Reserved.
+#
+#    Licensed under the Apache License, Version 2.0 (the "License"); you may
+#    not use this file except in compliance with the License. You may obtain
+#    a copy of the License at
+#
+#         http://www.apache.org/licenses/LICENSE-2.0
+#
+#    Unless required by applicable law or agreed to in writing, software
+#    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+#    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+#    License for the specific language governing permissions and limitations
+#    under the License.
+
+
+from taskflow.blocks import base
+
+
+class Pattern(base.Block):
+    """Base class for patterns that can contain nested blocks
+
+    Patterns put child blocks into *structure*.
+    """
+
+    def __init__(self):
+        super(Pattern, self).__init__()
+        self._children = []
+
+    @property
+    def children(self):
+        return self._children
+
+    def add(self, *children):
+        self._children.extend(children)
+        return self
+
+
+class LinearFlow(Pattern):
+    """Linear (sequential) pattern
+
+    Children of this pattern should be executed one after another,
+    in order. Every child implicitly depends on all the children
+    before it.
+    """
+
+
+class ParallelFlow(Pattern):
+    """Parallel (unordered) pattern
+
+    Children of this pattern are independent, and thus can be
+    executed in any order or in parallel.
+    """
diff --git a/taskflow/blocks/task.py b/taskflow/blocks/task.py
new file mode 100644
index 00000000..bb8ebb57
--- /dev/null
+++ b/taskflow/blocks/task.py
@@ -0,0 +1,47 @@
+
+# -*- coding: utf-8 -*-
+
+# vim: tabstop=4 shiftwidth=4 softtabstop=4
+
+#    Copyright (C) 2012-2013 Yahoo! Inc. All Rights Reserved.
+#
+#    Licensed under the Apache License, Version 2.0 (the "License"); you may
+#    not use this file except in compliance with the License. You may obtain
+#    a copy of the License at
+#
+#         http://www.apache.org/licenses/LICENSE-2.0
+#
+#    Unless required by applicable law or agreed to in writing, software
+#    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+#    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+#    License for the specific language governing permissions and limitations
+#    under the License.
+
+"""Terminal blocks that actually run code
+"""
+
+from taskflow.blocks import base
+from taskflow.openstack.common import uuidutils
+
+
+class Task(base.Block):
+    """A block that wraps a single task
+
+    The task should be executed, and produced results should be saved.
+    """
+
+    def __init__(self, task, uuid=None):
+        super(Task, self).__init__()
+        self._task = task
+        if uuid is None:
+            self._id = uuidutils.generate_uuid()
+        else:
+            self._id = str(uuid)
+
+    @property
+    def task(self):
+        return self._task
+
+    @property
+    def uuid(self):
+        return self._id
diff --git a/taskflow/engines/__init__.py b/taskflow/engines/__init__.py
new file mode 100644
index 00000000..830dd2e7
--- /dev/null
+++ b/taskflow/engines/__init__.py
@@ -0,0 +1,17 @@
+# -*- coding: utf-8 -*-
+
+# vim: tabstop=4 shiftwidth=4 softtabstop=4
+
+#    Copyright (C) 2012 Yahoo! Inc. All Rights Reserved.
+#
+#    Licensed under the Apache License, Version 2.0 (the "License"); you may
+#    not use this file except in compliance with the License. You may obtain
+#    a copy of the License at
+#
+#         http://www.apache.org/licenses/LICENSE-2.0
+#
+#    Unless required by applicable law or agreed to in writing, software
+#    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+#    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+#    License for the specific language governing permissions and limitations
+#    under the License.
diff --git a/taskflow/engines/action_engine/__init__.py b/taskflow/engines/action_engine/__init__.py
new file mode 100644
index 00000000..830dd2e7
--- /dev/null
+++ b/taskflow/engines/action_engine/__init__.py
@@ -0,0 +1,17 @@
+# -*- coding: utf-8 -*-
+
+# vim: tabstop=4 shiftwidth=4 softtabstop=4
+
+#    Copyright (C) 2012 Yahoo! Inc. All Rights Reserved.
+#
+#    Licensed under the Apache License, Version 2.0 (the "License"); you may
+#    not use this file except in compliance with the License. You may obtain
+#    a copy of the License at
+#
+#         http://www.apache.org/licenses/LICENSE-2.0
+#
+#    Unless required by applicable law or agreed to in writing, software
+#    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+#    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+#    License for the specific language governing permissions and limitations
+#    under the License.
diff --git a/taskflow/engines/action_engine/base_action.py b/taskflow/engines/action_engine/base_action.py
new file mode 100644
index 00000000..97f1f7e4
--- /dev/null
+++ b/taskflow/engines/action_engine/base_action.py
@@ -0,0 +1,34 @@
+# -*- coding: utf-8 -*-
+
+# vim: tabstop=4 shiftwidth=4 softtabstop=4
+
+#    Copyright (C) 2012 Yahoo! Inc. All Rights Reserved.
+#
+#    Licensed under the Apache License, Version 2.0 (the "License"); you may
+#    not use this file except in compliance with the License. You may obtain
+#    a copy of the License at
+#
+#         http://www.apache.org/licenses/LICENSE-2.0
+#
+#    Unless required by applicable law or agreed to in writing, software
+#    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+#    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+#    License for the specific language governing permissions and limitations
+#    under the License.
+
+
+import abc
+
+
+class Action(object):
+    """Basic action class
+    """
+    __metaclass__ = abc.ABCMeta
+
+    @abc.abstractmethod
+    def execute(self, engine):
+        """Run the action"""
+
+    @abc.abstractmethod
+    def revert(self, engine):
+        """Undo all side effects of execute method"""
diff --git a/taskflow/engines/action_engine/engine.py b/taskflow/engines/action_engine/engine.py
new file mode 100644
index 00000000..e3886427
--- /dev/null
+++ b/taskflow/engines/action_engine/engine.py
@@ -0,0 +1,58 @@
+
+# -*- coding: utf-8 -*-
+
+# vim: tabstop=4 shiftwidth=4 softtabstop=4
+
+#    Copyright (C) 2012 Yahoo! Inc. All Rights Reserved.
+#
+#    Licensed under the Apache License, Version 2.0 (the "License"); you may
+#    not use this file except in compliance with the License. You may obtain
+#    a copy of the License at
+#
+#         http://www.apache.org/licenses/LICENSE-2.0
+#
+#    Unless required by applicable law or agreed to in writing, software
+#    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+#    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+#    License for the specific language governing permissions and limitations
+#    under the License.
+
+
+from taskflow.engines.action_engine import seq_action
+from taskflow.engines.action_engine import task_action
+
+from taskflow import blocks
+from taskflow import states
+
+
+class ActionEngine(object):
+    """Generic action-based engine
+
+    Converts the flow to recursive structure of actions.
+    """
+
+    def __init__(self, flow, action_map):
+        self._action_map = action_map
+        self._root = self._to_action(flow)
+
+    def _to_action(self, pattern):
+        try:
+            factory = self._action_map[type(pattern)]
+        except KeyError:
+            raise ValueError('Action of unknown type: %s (type %s)'
+                             % (pattern, type(pattern)))
+        return factory(pattern, self._to_action)
+
+    def run(self):
+        status = self._root.execute(self)
+        if status == states.FAILURE:
+            self._root.revert(self)
+
+
+class SingleThreadedActionEngine(ActionEngine):
+    def __init__(self, flow):
+        ActionEngine.__init__(self, flow, {
+            blocks.Task: task_action.TaskAction,
+            blocks.LinearFlow: seq_action.SequentialAction,
+            blocks.ParallelFlow: seq_action.SequentialAction
+        })
diff --git a/taskflow/engines/action_engine/seq_action.py b/taskflow/engines/action_engine/seq_action.py
new file mode 100644
index 00000000..b68a96bd
--- /dev/null
+++ b/taskflow/engines/action_engine/seq_action.py
@@ -0,0 +1,43 @@
+# -*- coding: utf-8 -*-
+
+# vim: tabstop=4 shiftwidth=4 softtabstop=4
+
+#    Copyright (C) 2012 Yahoo! Inc. All Rights Reserved.
+#
+#    Licensed under the Apache License, Version 2.0 (the "License"); you may
+#    not use this file except in compliance with the License. You may obtain
+#    a copy of the License at
+#
+#         http://www.apache.org/licenses/LICENSE-2.0
+#
+#    Unless required by applicable law or agreed to in writing, software
+#    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+#    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+#    License for the specific language governing permissions and limitations
+#    under the License.
+
+from taskflow.engines.action_engine import base_action as base
+from taskflow import states
+
+
+class SequentialAction(base.Action):
+
+    def __init__(self, pattern, to_action):
+        self._history = []
+        self._actions = [to_action(pat) for pat in pattern.children]
+
+    def execute(self, engine):
+        state = states.SUCCESS
+        for action in self._actions:
+            #TODO(imelnikov): save history to storage
+            self._history.append(action)
+            state = action.execute(engine)
+            if state != states.SUCCESS:
+                break
+        return state
+
+    def revert(self, engine):
+        while self._history:
+            action = self._history[-1]
+            action.revert(engine)
+            self._history.pop()
diff --git a/taskflow/engines/action_engine/task_action.py b/taskflow/engines/action_engine/task_action.py
new file mode 100644
index 00000000..efb2fd73
--- /dev/null
+++ b/taskflow/engines/action_engine/task_action.py
@@ -0,0 +1,59 @@
+# -*- coding: utf-8 -*-
+
+# vim: tabstop=4 shiftwidth=4 softtabstop=4
+
+#    Copyright (C) 2012 Yahoo! Inc. All Rights Reserved.
+#
+#    Licensed under the Apache License, Version 2.0 (the "License"); you may
+#    not use this file except in compliance with the License. You may obtain
+#    a copy of the License at
+#
+#         http://www.apache.org/licenses/LICENSE-2.0
+#
+#    Unless required by applicable law or agreed to in writing, software
+#    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+#    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+#    License for the specific language governing permissions and limitations
+#    under the License.
+
+from taskflow.engines.action_engine import base_action as base
+from taskflow import states
+
+import sys
+
+
+class TaskAction(base.Action):
+
+    def __init__(self, block, _to_action):
+        self._task = block.task
+        if isinstance(self._task, type):
+            self._task = self._task()
+        self.state = states.PENDING
+
+    def execute(self, engine):
+        # TODO(imelnikov): notifications
+        self.state = states.RUNNING
+        try:
+            # TODO(imelnikov): pass only necessary args to task
+            self._task.execute()
+        except Exception:
+            # TODO(imelnikov): save exception information
+            print sys.exc_info()
+            self.state = states.FAILURE
+        else:
+            self.state = states.SUCCESS
+        return self.state
+
+    def revert(self, engine):
+        if self.state == states.PENDING:  # pragma: no cover
+            # NOTE(imelnikov): in all the other states, the task
+            #  execution was at least attempted, so we should give
+            #  task a chance for cleanup
+            return
+        try:
+            self._task.revert()
+        except Exception:
+            self.state = states.FAILURE
+            raise
+        else:
+            self.state = states.PENDING
diff --git a/taskflow/patterns/distributed_flow.py b/taskflow/patterns/distributed_flow.py
index e6699a2c..56ce2657 100644
--- a/taskflow/patterns/distributed_flow.py
+++ b/taskflow/patterns/distributed_flow.py
@@ -20,7 +20,6 @@
 import celery
 import logging
 
-
 LOG = logging.getLogger(__name__)
 
 
diff --git a/taskflow/tests/unit/test_action_engine.py b/taskflow/tests/unit/test_action_engine.py
new file mode 100644
index 00000000..ef104399
--- /dev/null
+++ b/taskflow/tests/unit/test_action_engine.py
@@ -0,0 +1,148 @@
+# -*- coding: utf-8 -*-
+
+# vim: tabstop=4 shiftwidth=4 softtabstop=4
+
+#    Copyright (C) 2012 Yahoo! Inc. All Rights Reserved.
+#
+#    Licensed under the Apache License, Version 2.0 (the "License"); you may
+#    not use this file except in compliance with the License. You may obtain
+#    a copy of the License at
+#
+#         http://www.apache.org/licenses/LICENSE-2.0
+#
+#    Unless required by applicable law or agreed to in writing, software
+#    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+#    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+#    License for the specific language governing permissions and limitations
+#    under the License.
+
+from taskflow import blocks
+from taskflow import task
+from taskflow import test
+
+from taskflow.engines.action_engine import engine as eng
+
+
+class TestTask(task.Task):
+
+    def __init__(self, values, name):
+        super(TestTask, self).__init__(name)
+        self.values = values
+
+    def execute(self, **kwargs):
+        self.values.append(self.name)
+        return 5
+
+    def revert(self, **kwargs):
+        self.values.append(self.name + ' reverted')
+
+
+class FailingTask(TestTask):
+    def execute(self, **kwargs):
+        raise RuntimeError('Woot!')
+
+
+class NeverRunningTask(task.Task):
+    def execute(self, **kwargs):
+        assert False, 'This method should not be called'
+
+    def revert(self, **kwargs):
+        assert False, 'This method should not be called'
+
+
+class NastyTask(task.Task):
+    def execute(self, **kwargs):
+        pass
+
+    def revert(self, **kwargs):
+        raise RuntimeError('Gotcha!')
+
+
+class EngineTestBase(object):
+    def setUp(self):
+        super(EngineTestBase, self).setUp()
+        self.values = []
+
+    def _make_engine(self, _flow):
+        raise NotImplementedError()
+
+
+class EngineTaskTest(EngineTestBase):
+
+    def test_run_task_as_flow(self):
+        flow = blocks.Task(TestTask(self.values, name='task1'))
+        self._make_engine(flow).run()
+        self.assertEquals(self.values, ['task1'])
+
+    def test_invalid_block_raises(self):
+        value = 'i am string, not block, sorry'
+        flow = blocks.LinearFlow().add(value)
+        with self.assertRaises(ValueError) as err:
+            self._make_engine(flow)
+        self.assertIn(value, str(err.exception))
+
+
+class EngineLinearFlowTest(EngineTestBase):
+
+    def test_sequential_flow_one_task(self):
+        flow = blocks.LinearFlow().add(
+            blocks.Task(TestTask(self.values, name='task1'))
+        )
+        self._make_engine(flow).run()
+        self.assertEquals(self.values, ['task1'])
+
+    def test_sequential_flow_two_tasks(self):
+        flow = blocks.LinearFlow().add(
+            blocks.Task(TestTask(self.values, name='task1')),
+            blocks.Task(TestTask(self.values, name='task2'))
+        )
+        self._make_engine(flow).run()
+        self.assertEquals(self.values, ['task1', 'task2'])
+
+    def test_sequential_flow_nested_blocks(self):
+        flow = blocks.LinearFlow().add(
+            blocks.Task(TestTask(self.values, 'task1')),
+            blocks.LinearFlow().add(
+                blocks.Task(TestTask(self.values, 'task2'))
+            )
+        )
+        self._make_engine(flow).run()
+        self.assertEquals(self.values, ['task1', 'task2'])
+
+    def test_revert_exception_is_reraised(self):
+        flow = blocks.LinearFlow().add(
+            blocks.Task(NastyTask),
+            blocks.Task(FailingTask(self.values, 'fail'))
+        )
+        engine = self._make_engine(flow)
+        with self.assertRaisesRegexp(RuntimeError, '^Gotcha'):
+            engine.run()
+
+    def test_revert_not_run_task_is_not_reverted(self):
+        flow = blocks.LinearFlow().add(
+            blocks.Task(FailingTask(self.values, 'fail')),
+            blocks.Task(NeverRunningTask)
+        )
+        self._make_engine(flow).run()
+        self.assertEquals(self.values, ['fail reverted'])
+
+    def test_correctly_reverts_children(self):
+        flow = blocks.LinearFlow().add(
+            blocks.Task(TestTask(self.values, 'task1')),
+            blocks.LinearFlow().add(
+                blocks.Task(TestTask(self.values, 'task2')),
+                blocks.Task(FailingTask(self.values, 'fail'))
+            )
+        )
+        engine = self._make_engine(flow)
+        engine.run()
+        self.assertEquals(self.values, ['task1', 'task2',
+                                        'fail reverted',
+                                        'task2 reverted', 'task1 reverted'])
+
+
+class SingleThreadedEngineTest(EngineTaskTest,
+                               EngineLinearFlowTest,
+                               test.TestCase):
+    def _make_engine(self, flow):
+        return eng.SingleThreadedActionEngine(flow)
diff --git a/tox.ini b/tox.ini
index ada78a29..ee1dfb58 100644
--- a/tox.ini
+++ b/tox.ini
@@ -39,6 +39,6 @@ setenv = NOSE_WITH_COVERAGE=1
 commands = {posargs}
 
 [flake8]
-ignore = H402,H302
+ignore = H402
 builtins = _
-exclude = .venv,.tox,dist,doc,*openstack/common*,*egg,.git,build,tools
\ No newline at end of file
+exclude = .venv,.tox,dist,doc,*openstack/common*,*egg,.git,build,tools