diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index 8a96c835af5..9ad9ddf09e0 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -4,7 +4,8 @@ The Python special interest group (SIG) meets regularly. See the OpenTelemetry
 [community](https://github.com/open-telemetry/community#python-sdk) repo for
 information on this and other language SIGs.
 
-See the [public meeting notes](https://docs.google.com/document/d/1CIMGoIOZ-c3-igzbd6_Pnxx1SjAkjwqoYSUWxPY8XIs/edit)
+See the [public meeting
+notes](https://docs.google.com/document/d/1CIMGoIOZ-c3-igzbd6_Pnxx1SjAkjwqoYSUWxPY8XIs/edit)
 for a summary description of past meetings. To request edit access join the
 meeting or get in touch on Gitter.
 
@@ -22,9 +23,9 @@ The standard Python unittest module is used to author unit tests.
 ## Design Choices
 
 As with other OpenTelemetry clients, opentelemetry-python follows the 
-[opentelemetry-specification](https://github.com/open-telemetry/opentelemetry-specification).
+(opentelemetry-specification)[https://github.com/open-telemetry/opentelemetry-specification].
 
-It's especially valuable to read through the [library guidelines](https://github.com/open-telemetry/opentelemetry-specification/blob/master/specification/library-guidelines.md).
+It's especially valuable to read through the (library guidelines)[https://github.com/open-telemetry/opentelemetry-specification/blob/master/specification/library-guidelines.md].
 
 ### Focus on Capabilities, Not Structure Compliance
 
@@ -43,4 +44,4 @@ For a deeper discussion, see: https://github.com/open-telemetry/opentelemetry-sp
 ## Styleguide
 
 * docstrings should adhere to the Google styleguide as specified
-  with the [napolean extension](http://www.sphinx-doc.org/en/master/usage/extensions/napoleon.html#google-vs-numpy) extension in [Sphinx](http://www.sphinx-doc.org/en/master/index.html).
\ No newline at end of file
+  with the (napolean extension)[http://www.sphinx-doc.org/en/master/usage/extensions/napoleon.html#google-vs-numpy] extension in (Sphinx)[http://www.sphinx-doc.org/en/master/index.html].
\ No newline at end of file
diff --git a/README.md b/README.md
index edea6801e32..e04d9e3cc6d 100644
--- a/README.md
+++ b/README.md
@@ -8,4 +8,4 @@ The Python [OpenTelemetry](https://opentelemetry.io/) client.
 
 ## Contributing
 
-See [CONTRIBUTING.md](CONTRIBUTING.md)
\ No newline at end of file
+See (CONTRIBUTING.md)[CONTRIBUTING.md]
\ No newline at end of file
diff --git a/docs/index.rst b/docs/index.rst
index 8991f2b5df5..90385dba4a9 100644
--- a/docs/index.rst
+++ b/docs/index.rst
@@ -15,9 +15,8 @@ abstract types for OpenTelemetry implementations.
    :maxdepth: 1
    :caption: Contents:
 
-   opentelemetry.context
-   opentelemetry.loader
    opentelemetry.trace
+   opentelemetry.loader
 
 
 Indices and tables
diff --git a/docs/opentelemetry.context.base_context.rst b/docs/opentelemetry.context.base_context.rst
deleted file mode 100644
index ac28d40008e..00000000000
--- a/docs/opentelemetry.context.base_context.rst
+++ /dev/null
@@ -1,7 +0,0 @@
-opentelemetry.context.base\_context module
-==========================================
-
-.. automodule:: opentelemetry.context.base_context
-    :members:
-    :undoc-members:
-    :show-inheritance:
diff --git a/docs/opentelemetry.context.rst b/docs/opentelemetry.context.rst
deleted file mode 100644
index 7bc738a0500..00000000000
--- a/docs/opentelemetry.context.rst
+++ /dev/null
@@ -1,14 +0,0 @@
-opentelemetry.context package
-=============================
-
-Submodules
-----------
-
-.. toctree::
-
-   opentelemetry.context.base_context
-
-Module contents
----------------
-
-.. automodule:: opentelemetry.context
diff --git a/opentelemetry-api/src/opentelemetry/context/__init__.py b/opentelemetry-api/src/opentelemetry/context/__init__.py
index 4edbf2bd048..9a58d4f23b5 100644
--- a/opentelemetry-api/src/opentelemetry/context/__init__.py
+++ b/opentelemetry-api/src/opentelemetry/context/__init__.py
@@ -11,15 +11,13 @@
 # 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.
-
-
 """
 The OpenTelemetry context module provides abstraction layer on top of
 thread-local storage and contextvars. The long term direction is to switch to
 contextvars provided by the Python runtime library.
 
 A global object ``Context`` is provided to access all the context related
-functionalities::
+functionalities:
 
     >>> from opentelemetry.context import Context
     >>> Context.foo = 1
@@ -27,9 +25,8 @@
     >>> Context.foo
     2
 
-When explicit thread is used, a helper function
-``Context.with_current_context`` can be used to carry the context across
-threads::
+When explicit thread is used, a helper function `Context.with_current_context`
+can be used to carry the context across threads:
 
     from threading import Thread
     from opentelemetry.context import Context
@@ -62,7 +59,7 @@ def work(name):
 
         print('Main thread:', Context)
 
-Here goes another example using thread pool::
+Here goes another example using thread pool:
 
     import time
     import threading
@@ -97,7 +94,7 @@ def work(name):
         pool.join()
         println('Main thread: {}'.format(Context))
 
-Here goes a simple demo of how async could work in Python 3.7+::
+Here goes a simple demo of how async could work in Python 3.7+:
 
     import asyncio
 
@@ -141,9 +138,9 @@ async def main():
 import typing
 
 from .base_context import BaseRuntimeContext
+from .unified_context import UnifiedContext
 
-__all__ = ['Context']
-
+__all__ = ['Context', 'UnifiedContext']
 
 Context: typing.Optional[BaseRuntimeContext]
 
diff --git a/opentelemetry-api/src/opentelemetry/context/base_context.py b/opentelemetry-api/src/opentelemetry/context/base_context.py
index bb5703e7c32..35ee179a4b8 100644
--- a/opentelemetry-api/src/opentelemetry/context/base_context.py
+++ b/opentelemetry-api/src/opentelemetry/context/base_context.py
@@ -37,7 +37,7 @@ def set(self, value: 'object') -> None:
             raise NotImplementedError
 
     _lock = threading.Lock()
-    _slots: typing.Dict[str, 'BaseRuntimeContext.Slot'] = {}
+    _slots: typing.Dict[str, Slot] = {}
 
     @classmethod
     def clear(cls) -> None:
@@ -48,11 +48,7 @@ def clear(cls) -> None:
             slot.clear()
 
     @classmethod
-    def register_slot(
-            cls,
-            name: str,
-            default: 'object' = None,
-    ) -> 'BaseRuntimeContext.Slot':
+    def register_slot(cls, name: str, default: 'object' = None) -> 'Slot':
         """Register a context slot with an optional default value.
 
         :type name: str
diff --git a/opentelemetry-api/src/opentelemetry/context/propagation/binaryformat.py b/opentelemetry-api/src/opentelemetry/context/propagation/binaryformat.py
index f05ef699721..b3e8b27ec3d 100644
--- a/opentelemetry-api/src/opentelemetry/context/propagation/binaryformat.py
+++ b/opentelemetry-api/src/opentelemetry/context/propagation/binaryformat.py
@@ -13,9 +13,8 @@
 # limitations under the License.
 
 import abc
-import typing
 
-from opentelemetry.trace import SpanContext
+from opentelemetry.context import UnifiedContext
 
 
 class BinaryFormat(abc.ABC):
@@ -26,14 +25,14 @@ class BinaryFormat(abc.ABC):
     """
     @staticmethod
     @abc.abstractmethod
-    def to_bytes(context: SpanContext) -> bytes:
+    def to_bytes(context: UnifiedContext) -> bytes:
         """Creates a byte representation of a SpanContext.
 
         to_bytes should read values from a SpanContext and return a data
         format to represent it, in bytes.
 
         Args:
-            context: the SpanContext to serialize
+            context: the SpanContext to serialize.
 
         Returns:
             A bytes representation of the SpanContext.
@@ -41,15 +40,17 @@ def to_bytes(context: SpanContext) -> bytes:
         """
     @staticmethod
     @abc.abstractmethod
-    def from_bytes(byte_representation: bytes) -> typing.Optional[SpanContext]:
-        """Return a SpanContext that was represented by bytes.
+    def from_bytes(context: UnifiedContext,
+                   byte_representation: bytes) -> None:
+        """Populate UnifiedContext that was represented by bytes.
 
-        from_bytes should return back a SpanContext that was constructed from
-        the data serialized in the byte_representation passed. If it is not
+        from_bytes should populated UnifiedContext with data that was
+        serialized in the byte_representation passed. If it is not
         possible to read in a proper SpanContext, return None.
 
         Args:
-            byte_representation: the bytes to deserialize
+            context: The UnifiedContext to populate.
+            byte_representation: the bytes to deserialize.
 
         Returns:
             A bytes representation of the SpanContext if it is valid.
diff --git a/opentelemetry-api/src/opentelemetry/context/propagation/httptextformat.py b/opentelemetry-api/src/opentelemetry/context/propagation/httptextformat.py
index 860498fe35d..023e0bab728 100644
--- a/opentelemetry-api/src/opentelemetry/context/propagation/httptextformat.py
+++ b/opentelemetry-api/src/opentelemetry/context/propagation/httptextformat.py
@@ -15,6 +15,7 @@
 import abc
 import typing
 
+from opentelemetry.context import UnifiedContext
 from opentelemetry.trace import SpanContext
 
 Setter = typing.Callable[[object, str, str], None]
@@ -35,11 +36,12 @@ class HTTPTextFormat(abc.ABC):
         import flask
         import requests
         from opentelemetry.context.propagation import HTTPTextFormat
+        from opentelemetry.trace import tracer
+        from opentelemetry.context import UnifiedContext
 
         PROPAGATOR = HTTPTextFormat()
 
 
-
         def get_header_from_flask_request(request, key):
             return request.headers.get_all(key)
 
@@ -48,15 +50,17 @@ def set_header_into_requests_request(request: requests.Request,
             request.headers[key] = value
 
         def example_route():
-            span_context = PROPAGATOR.extract(
-                get_header_from_flask_request,
+            span = tracer().create_span("")
+            context = UnifiedContext.create(span)
+            PROPAGATOR.extract(
+                context, get_header_from_flask_request,
                 flask.request
             )
             request_to_downstream = requests.Request(
                 "GET", "http://httpbin.org/get"
             )
             PROPAGATOR.inject(
-                span_context,
+                context,
                 set_header_into_requests_request,
                 request_to_downstream
             )
@@ -68,15 +72,17 @@ def example_route():
        https://github.com/open-telemetry/opentelemetry-specification/blob/master/specification/api-propagators.md
     """
     @abc.abstractmethod
-    def extract(self, get_from_carrier: Getter,
-                carrier: object) -> SpanContext:
-        """Create a SpanContext from values in the carrier.
+    def extract(self, context: UnifiedContext, get_from_carrier: Getter,
+                carrier: object) -> None:
+        """Extract values from the carrier into the context.
 
         The extract function should retrieve values from the carrier
-        object using get_from_carrier, and use values to populate a
-        SpanContext value and return it.
+        object using get_from_carrier, and use values to populate
+        attributes of the UnifiedContext passed in.
 
         Args:
+            context: A UnifiedContext instance that will be
+                populated with values from the carrier.
             get_from_carrier: a function that can retrieve zero
                 or more values from the carrier. In the case that
                 the value does not exist, return an empty list.
diff --git a/opentelemetry-api/src/opentelemetry/context/unified_context.py b/opentelemetry-api/src/opentelemetry/context/unified_context.py
new file mode 100644
index 00000000000..7da5200d254
--- /dev/null
+++ b/opentelemetry-api/src/opentelemetry/context/unified_context.py
@@ -0,0 +1,65 @@
+# Copyright 2019, OpenTelemetry Authors
+#
+# 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 opentelemetry.distributedcontext import DistributedContext
+from opentelemetry.trace import SpanContext
+
+
+class UnifiedContext:
+    """A unified context object that contains all context relevant to
+    telemetry.
+
+    The UnifiedContext is a single object that composes all contexts that
+    are needed by the various forms of telemetry. It is intended to be an
+    object that can be passed as the argument to any component that needs
+    to read or modify content values (such as propagators). By unifying
+    all context in a composed data structure, it expands the flexibility
+    of the APIs that modify it.
+
+    As it is designed to carry context specific to all telemetry use
+    cases, it's schema is explicit. Note that this is not intended to
+    be an object that acts as a singleton that returns different results
+    based on the thread or coroutine of execution. For that, see `Context`.
+
+
+    Args:
+        distributed: The DistributedContext for this instance.
+        span: The SpanContext for this instance.
+    """
+    __slots__ = ["distributed", "span"]
+
+    def __init__(self, distributed: DistributedContext, span: SpanContext):
+        self.distributed = distributed
+        self.span = span
+
+    @staticmethod
+    def create(span: SpanContext) -> "UnifiedContext":
+        """Create an unpopulated UnifiedContext object.
+
+        Example:
+
+            from opentelemetry.trace import tracer
+            span = tracer.create_span("")
+            context = UnifiedContext.create(span)
+
+
+        Args:
+            parent_span: the parent SpanContext that will be the
+                parent of the span in the UnifiedContext.
+        """
+        return UnifiedContext(DistributedContext(), span)
+
+    def __repr__(self) -> str:
+        return "{}(distributed={}, span={})".format(
+            type(self).__name__, repr(self.distributed), repr(self.span))
diff --git a/opentelemetry-api/src/opentelemetry/distributedcontext/__init__.py b/opentelemetry-api/src/opentelemetry/distributedcontext/__init__.py
index d853a7bcf65..9efd00db658 100644
--- a/opentelemetry-api/src/opentelemetry/distributedcontext/__init__.py
+++ b/opentelemetry-api/src/opentelemetry/distributedcontext/__init__.py
@@ -11,3 +11,9 @@
 # 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 DistributedContext:
+    """A container for values for w3c's Correlation Context."""
+    def __repr__(self) -> str:
+        return "{}()".format(type(self).__name__)
diff --git a/opentelemetry-api/src/opentelemetry/trace/__init__.py b/opentelemetry-api/src/opentelemetry/trace/__init__.py
index aed421307ee..f5f082b77ca 100644
--- a/opentelemetry-api/src/opentelemetry/trace/__init__.py
+++ b/opentelemetry-api/src/opentelemetry/trace/__init__.py
@@ -11,7 +11,6 @@
 # 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.
-
 """
 The OpenTelemetry tracing API describes the classes used to generate
 distributed traces.
@@ -33,9 +32,9 @@
     from opentelemetry.trace import tracer
 
     # Create a new root span, set it as the current span in context
-    with tracer.start_span("parent"):
+    with tracer().start_span("parent"):
         # Attach a new child and update the current span
-        with tracer.start_span("child"):
+        with tracer().start_span("child"):
             do_work():
         # Close child span, set parent as current
     # Close parent span, set default span as current
@@ -46,7 +45,7 @@
     from opentelemetry.api.trace import tracer
 
     # Explicit parent span assignment
-    span = tracer.create_span("child", parent=parent) as child:
+    span = tracer().create_span("child", parent=parent) as child:
 
     # The caller is responsible for starting and ending the span
     span.start()
@@ -65,7 +64,6 @@
 import typing
 
 from opentelemetry import loader
-from opentelemetry import types
 
 # TODO: quarantine
 ParentSpan = typing.Optional[typing.Union['Span', 'SpanContext']]
@@ -73,7 +71,6 @@
 
 class Span:
     """A span represents a single operation within a trace."""
-
     def start(self) -> None:
         """Sets the current time as the span's start time.
 
@@ -83,7 +80,6 @@ def start(self) -> None:
         Only the first call to `start` should modify the span, and
         implementations are free to ignore or raise on further calls.
         """
-
     def end(self) -> None:
         """Sets the current time as the span's end time.
 
@@ -92,7 +88,6 @@ def end(self) -> None:
         Only the first call to `end` should modify the span, and
         implementations are free to ignore or raise on further calls.
         """
-
     def get_context(self) -> 'SpanContext':
         """Gets the span's SpanContext.
 
@@ -103,35 +98,6 @@ def get_context(self) -> 'SpanContext':
             A :class:`.SpanContext` with a copy of this span's immutable state.
         """
 
-    def set_attribute(self: 'Span',
-                      key: str,
-                      value: types.AttributeValue,
-                      ) -> None:
-        """Sets an Attribute.
-
-        Sets a single Attribute with the key and value passed as arguments.
-        """
-
-    def add_event(self: 'Span',
-                  name: str,
-                  attributes: types.Attributes = None,
-                  ) -> None:
-        """Adds an Event.
-
-        Adds a single Event with the name and, optionally, attributes passed
-        as arguments.
-        """
-
-    def add_link(self: 'Span',
-                 link_target_context: 'SpanContext',
-                 attributes: types.Attributes = None,
-                 ) -> None:
-        """Adds a Link to another span.
-
-        Adds a single Link from this Span to another Span identified by the
-        `SpanContext` passed as argument.
-        """
-
 
 class TraceOptions(int):
     """A bitmask that represents options specific to the trace.
@@ -165,7 +131,6 @@ class TraceState(typing.Dict[str, str]):
     .. _W3C Trace Context - Tracestate:
         https://www.w3.org/TR/trace-context/#tracestate-field
     """
-
     @classmethod
     def get_default(cls) -> 'TraceState':
         return cls()
@@ -194,13 +159,11 @@ class SpanContext:
         options: Trace options to propagate.
         state: Tracing-system-specific info to propagate.
     """
-
     def __init__(self,
                  trace_id: int,
                  span_id: int,
                  trace_options: 'TraceOptions' = None,
-                 trace_state: 'TraceState' = None
-                 ) -> None:
+                 trace_state: 'TraceState' = None) -> None:
         if trace_options is None:
             trace_options = DEFAULT_TRACE_OPTIONS
         if trace_state is None:
@@ -211,12 +174,9 @@ def __init__(self,
         self.trace_state = trace_state
 
     def __repr__(self) -> str:
-        return ("{}(trace_id={}, span_id={})"
-                .format(
-                    type(self).__name__,
-                    format_trace_id(self.trace_id),
-                    format_span_id(self.span_id)
-                ))
+        return ("{}(trace_id={}, span_id={})".format(
+            type(self).__name__, format_trace_id(self.trace_id),
+            format_span_id(self.span_id)))
 
     def is_valid(self) -> bool:
         """Get whether this `SpanContext` is valid.
@@ -227,8 +187,8 @@ def is_valid(self) -> bool:
         Returns:
             True if the `SpanContext` is valid, false otherwise.
         """
-        return (self.trace_id != INVALID_TRACE_ID and
-                self.span_id != INVALID_SPAN_ID)
+        return (self.trace_id != INVALID_TRACE_ID
+                and self.span_id != INVALID_SPAN_ID)
 
 
 class DefaultSpan(Span):
@@ -271,13 +231,8 @@ def get_current_span(self) -> 'Span':
             The currently active :class:`.Span`, or a placeholder span with an
             invalid :class:`.SpanContext`.
         """
-        # pylint: disable=no-self-use
-        return INVALID_SPAN
-
     @contextmanager  # type: ignore
-    def start_span(self,
-                   name: str,
-                   parent: ParentSpan = CURRENT_SPAN
+    def start_span(self, name: str, parent: ParentSpan = CURRENT_SPAN
                    ) -> typing.Iterator['Span']:
         """Context manager for span creation.
 
@@ -321,13 +276,8 @@ def start_span(self,
         Yields:
             The newly-created span.
         """
-        # pylint: disable=unused-argument,no-self-use
-        yield INVALID_SPAN
-
-    def create_span(self,
-                    name: str,
-                    parent: ParentSpan = CURRENT_SPAN
-                    ) -> 'Span':
+    def create_span(self, name: str,
+                    parent: ParentSpan = CURRENT_SPAN) -> 'Span':
         """Creates a span.
 
         Creating the span does not start it, and should not affect the tracer's
@@ -358,9 +308,6 @@ def create_span(self,
         Returns:
             The newly-created span.
         """
-        # pylint: disable=unused-argument,no-self-use
-        return INVALID_SPAN
-
     @contextmanager  # type: ignore
     def use_span(self, span: 'Span') -> typing.Iterator[None]:
         """Context manager for controlling a span's lifetime.
@@ -374,8 +321,6 @@ def use_span(self, span: 'Span') -> typing.Iterator[None]:
         Args:
             span: The span to start and make current.
         """
-        # pylint: disable=unused-argument,no-self-use
-        yield
 
 
 _TRACER: typing.Optional[Tracer] = None
@@ -399,9 +344,8 @@ def tracer() -> Tracer:
 
 
 def set_preferred_tracer_implementation(
-        factory: typing.Callable[
-            [typing.Type[Tracer]], typing.Optional[Tracer]]
-        ) -> None:
+        factory: typing.Callable[[typing.Type[Tracer]], typing.
+                                 Optional[Tracer]]) -> None:
     """Set the factory to be used to create the tracer.
 
     See :mod:`opentelemetry.loader` for details.
diff --git a/opentelemetry-api/tests/trace/test_tracer.py b/opentelemetry-api/tests/trace/test_tracer.py
deleted file mode 100644
index f1aa402ffa5..00000000000
--- a/opentelemetry-api/tests/trace/test_tracer.py
+++ /dev/null
@@ -1,39 +0,0 @@
-# Copyright 2019, OpenTelemetry Authors
-#
-# 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 unittest
-
-from opentelemetry import trace
-
-
-class TestTracer(unittest.TestCase):
-    def setUp(self):
-        self.tracer = trace.Tracer()
-
-    def test_get_current_span(self):
-        span = self.tracer.get_current_span()
-        self.assertIsInstance(span, trace.Span)
-
-    def test_start_span(self):
-        with self.tracer.start_span("") as span:
-            self.assertIsInstance(span, trace.Span)
-
-    def test_create_span(self):
-        span = self.tracer.create_span("")
-        self.assertIsInstance(span, trace.Span)
-
-    def test_use_span(self):
-        span = trace.Span()
-        with self.tracer.use_span(span):
-            pass
diff --git a/opentelemetry-sdk/src/opentelemetry/sdk/context/propagation/b3_format.py b/opentelemetry-sdk/src/opentelemetry/sdk/context/propagation/b3_format.py
index eaeeb577d2b..23b2e5a73de 100644
--- a/opentelemetry-sdk/src/opentelemetry/sdk/context/propagation/b3_format.py
+++ b/opentelemetry-sdk/src/opentelemetry/sdk/context/propagation/b3_format.py
@@ -32,7 +32,7 @@ class B3Format(HTTPTextFormat):
     _SAMPLE_PROPAGATE_VALUES = set(["1", "True", "true", "d"])
 
     @classmethod
-    def extract(cls, get_from_carrier, carrier):
+    def extract(cls, context, get_from_carrier, carrier):
         trace_id = format_trace_id(trace.INVALID_TRACE_ID)
         span_id = format_span_id(trace.INVALID_SPAN_ID)
         sampled = 0
@@ -56,7 +56,7 @@ def extract(cls, get_from_carrier, carrier):
             elif len(fields) == 4:
                 trace_id, span_id, sampled, _parent_span_id = fields
             else:
-                return trace.INVALID_SPAN_CONTEXT
+                return
         else:
             trace_id = _extract_first_element(
                 get_from_carrier(carrier, cls.TRACE_ID_KEY)) or trace_id
@@ -75,7 +75,7 @@ def extract(cls, get_from_carrier, carrier):
         if sampled in cls._SAMPLE_PROPAGATE_VALUES or flags == "1":
             options |= trace.TraceOptions.RECORDED
 
-        return trace.SpanContext(
+        context.span = trace.SpanContext(
             # trace an span ids are encoded in hex, so must be converted
             trace_id=int(trace_id, 16),
             span_id=int(span_id, 16),
@@ -85,11 +85,12 @@ def extract(cls, get_from_carrier, carrier):
 
     @classmethod
     def inject(cls, context, set_in_carrier, carrier):
-        sampled = (trace.TraceOptions.RECORDED & context.trace_options) != 0
+        sampled = (trace.TraceOptions.RECORDED
+                   & context.span.trace_options) != 0
         set_in_carrier(carrier, cls.TRACE_ID_KEY,
-                       format_trace_id(context.trace_id))
+                       format_trace_id(context.span.trace_id))
         set_in_carrier(carrier, cls.SPAN_ID_KEY,
-                       format_span_id(context.span_id))
+                       format_span_id(context.span.span_id))
         set_in_carrier(carrier, cls.SAMPLED_KEY, "1" if sampled else "0")
 
 
diff --git a/opentelemetry-sdk/src/opentelemetry/sdk/trace/__init__.py b/opentelemetry-sdk/src/opentelemetry/sdk/trace/__init__.py
index 0a85c14c67b..44f321e6c96 100644
--- a/opentelemetry-sdk/src/opentelemetry/sdk/trace/__init__.py
+++ b/opentelemetry-sdk/src/opentelemetry/sdk/trace/__init__.py
@@ -230,7 +230,7 @@ def get_context(self):
 
     def set_attribute(self: 'Span',
                       key: str,
-                      value: types.AttributeValue,
+                      value: 'types.AttributeValue'
                       ) -> None:
         if self.attributes is Span.empty_attributes:
             self.attributes = BoundedDict(MAX_NUM_ATTRIBUTES)
@@ -238,26 +238,22 @@ def set_attribute(self: 'Span',
 
     def add_event(self: 'Span',
                   name: str,
-                  attributes: types.Attributes = None,
+                  attributes: 'types.Attributes',
                   ) -> None:
         if self.events is Span.empty_events:
             self.events = BoundedList(MAX_NUM_EVENTS)
-        if attributes is None:
-            attributes = Span.empty_attributes
         self.events.append(Event(name, attributes))
 
     def add_link(self: 'Span',
-                 link_target_context: 'trace_api.SpanContext',
-                 attributes: types.Attributes = None,
+                 context: 'trace_api.SpanContext',
+                 attributes: 'types.Attributes',
                  ) -> None:
         if self.links is Span.empty_links:
             self.links = BoundedList(MAX_NUM_LINKS)
-        if attributes is None:
-            attributes = Span.empty_attributes
-        self.links.append(Link(link_target_context, attributes))
+        self.links.append(Link(context, attributes))
 
     def start(self):
-        if self.start_time is None:
+        if self.end_time is None:
             self.start_time = util.time_ns()
 
     def end(self):
diff --git a/opentelemetry-sdk/tests/context/propagation/test_b3_format.py b/opentelemetry-sdk/tests/context/propagation/test_b3_format.py
index a24dd01c668..f98b078742e 100644
--- a/opentelemetry-sdk/tests/context/propagation/test_b3_format.py
+++ b/opentelemetry-sdk/tests/context/propagation/test_b3_format.py
@@ -17,6 +17,9 @@
 import opentelemetry.sdk.context.propagation.b3_format as b3_format
 import opentelemetry.sdk.trace as trace
 
+from opentelemetry.context import UnifiedContext
+from opentelemetry.sdk.trace import tracer
+
 FORMAT = b3_format.B3Format()
 
 
@@ -33,6 +36,11 @@ def setUpClass(cls):
         cls.serialized_span_id = b3_format.format_span_id(
             trace.generate_span_id())
 
+    def setUp(self):
+        span_context = tracer.create_span("").context
+        self.context = UnifiedContext.create(span_context)
+        self.carrier = {}
+
     def test_extract_multi_header(self):
         """Test the extraction of B3 headers."""
         carrier = {
@@ -40,14 +48,13 @@ def test_extract_multi_header(self):
             FORMAT.SPAN_ID_KEY: self.serialized_span_id,
             FORMAT.SAMPLED_KEY: "1",
         }
-        span_context = FORMAT.extract(get_as_list, carrier)
-        new_carrier = {}
-        FORMAT.inject(span_context, dict.__setitem__, new_carrier)
-        self.assertEqual(new_carrier[FORMAT.TRACE_ID_KEY],
+        FORMAT.extract(self.context, get_as_list, carrier)
+        FORMAT.inject(self.context, dict.__setitem__, self.carrier)
+        self.assertEqual(self.carrier[FORMAT.TRACE_ID_KEY],
                          self.serialized_trace_id)
-        self.assertEqual(new_carrier[FORMAT.SPAN_ID_KEY],
+        self.assertEqual(self.carrier[FORMAT.SPAN_ID_KEY],
                          self.serialized_span_id)
-        self.assertEqual(new_carrier[FORMAT.SAMPLED_KEY], "1")
+        self.assertEqual(self.carrier[FORMAT.SAMPLED_KEY], "1")
 
     def test_extract_single_header(self):
         """Test the extraction from a single b3 header."""
@@ -55,14 +62,13 @@ def test_extract_single_header(self):
             FORMAT.SINGLE_HEADER_KEY:
             "{}-{}".format(self.serialized_trace_id, self.serialized_span_id)
         }
-        span_context = FORMAT.extract(get_as_list, carrier)
-        new_carrier = {}
-        FORMAT.inject(span_context, dict.__setitem__, new_carrier)
-        self.assertEqual(new_carrier[FORMAT.TRACE_ID_KEY],
+        FORMAT.extract(self.context, get_as_list, carrier)
+        FORMAT.inject(self.context, dict.__setitem__, self.carrier)
+        self.assertEqual(self.carrier[FORMAT.TRACE_ID_KEY],
                          self.serialized_trace_id)
-        self.assertEqual(new_carrier[FORMAT.SPAN_ID_KEY],
+        self.assertEqual(self.carrier[FORMAT.SPAN_ID_KEY],
                          self.serialized_span_id)
-        self.assertEqual(new_carrier[FORMAT.SAMPLED_KEY], "1")
+        self.assertEqual(self.carrier[FORMAT.SAMPLED_KEY], "1")
 
     def test_extract_header_precedence(self):
         """A single b3 header should take precedence over multiple
@@ -79,10 +85,9 @@ def test_extract_header_precedence(self):
             FORMAT.SAMPLED_KEY:
             "1",
         }
-        span_context = FORMAT.extract(get_as_list, carrier)
-        new_carrier = {}
-        FORMAT.inject(span_context, dict.__setitem__, new_carrier)
-        self.assertEqual(new_carrier[FORMAT.TRACE_ID_KEY],
+        FORMAT.extract(self.context, get_as_list, carrier)
+        FORMAT.inject(self.context, dict.__setitem__, self.carrier)
+        self.assertEqual(self.carrier[FORMAT.TRACE_ID_KEY],
                          single_header_trace_id)
 
     def test_enabled_sampling(self):
@@ -93,10 +98,9 @@ def test_enabled_sampling(self):
                 FORMAT.SPAN_ID_KEY: self.serialized_span_id,
                 FORMAT.SAMPLED_KEY: variant,
             }
-            span_context = FORMAT.extract(get_as_list, carrier)
-            new_carrier = {}
-            FORMAT.inject(span_context, dict.__setitem__, new_carrier)
-            self.assertEqual(new_carrier[FORMAT.SAMPLED_KEY], "1")
+            FORMAT.extract(self.context, get_as_list, carrier)
+            FORMAT.inject(self.context, dict.__setitem__, self.carrier)
+            self.assertEqual(self.carrier[FORMAT.SAMPLED_KEY], "1")
 
     def test_disabled_sampling(self):
         """Test b3 sample key variants that turn off sampling."""
@@ -106,10 +110,9 @@ def test_disabled_sampling(self):
                 FORMAT.SPAN_ID_KEY: self.serialized_span_id,
                 FORMAT.SAMPLED_KEY: variant,
             }
-            span_context = FORMAT.extract(get_as_list, carrier)
-            new_carrier = {}
-            FORMAT.inject(span_context, dict.__setitem__, new_carrier)
-            self.assertEqual(new_carrier[FORMAT.SAMPLED_KEY], "0")
+            FORMAT.extract(self.context, get_as_list, carrier)
+            FORMAT.inject(self.context, dict.__setitem__, self.carrier)
+            self.assertEqual(self.carrier[FORMAT.SAMPLED_KEY], "0")
 
     def test_flags(self):
         """x-b3-flags set to "1" should result in propagation."""
@@ -118,10 +121,9 @@ def test_flags(self):
             FORMAT.SPAN_ID_KEY: self.serialized_span_id,
             FORMAT.FLAGS_KEY: "1",
         }
-        span_context = FORMAT.extract(get_as_list, carrier)
-        new_carrier = {}
-        FORMAT.inject(span_context, dict.__setitem__, new_carrier)
-        self.assertEqual(new_carrier[FORMAT.SAMPLED_KEY], "1")
+        FORMAT.extract(self.context, get_as_list, carrier)
+        FORMAT.inject(self.context, dict.__setitem__, self.carrier)
+        self.assertEqual(self.carrier[FORMAT.SAMPLED_KEY], "1")
 
     def test_flags_and_sampling(self):
         """Propagate if b3 flags and sampling are set."""
@@ -130,10 +132,9 @@ def test_flags_and_sampling(self):
             FORMAT.SPAN_ID_KEY: self.serialized_span_id,
             FORMAT.FLAGS_KEY: "1",
         }
-        span_context = FORMAT.extract(get_as_list, carrier)
-        new_carrier = {}
-        FORMAT.inject(span_context, dict.__setitem__, new_carrier)
-        self.assertEqual(new_carrier[FORMAT.SAMPLED_KEY], "1")
+        FORMAT.extract(self.context, get_as_list, carrier)
+        FORMAT.inject(self.context, dict.__setitem__, self.carrier)
+        self.assertEqual(self.carrier[FORMAT.SAMPLED_KEY], "1")
 
     def test_64bit_trace_id(self):
         """64 bit trace ids should be padded to 128 bit trace ids."""
@@ -143,20 +144,22 @@ def test_64bit_trace_id(self):
             FORMAT.SPAN_ID_KEY: self.serialized_span_id,
             FORMAT.FLAGS_KEY: "1",
         }
-        span_context = FORMAT.extract(get_as_list, carrier)
-        new_carrier = {}
-        FORMAT.inject(span_context, dict.__setitem__, new_carrier)
-        self.assertEqual(new_carrier[FORMAT.TRACE_ID_KEY],
+        FORMAT.extract(self.context, get_as_list, carrier)
+        FORMAT.inject(self.context, dict.__setitem__, self.carrier)
+        self.assertEqual(self.carrier[FORMAT.TRACE_ID_KEY],
                          "0" * 16 + trace_id_64_bit)
 
     def test_invalid_single_header(self):
         """If an invalid single header is passed, return an
         invalid SpanContext.
         """
+        self.context.span.trace_id = api_trace.INVALID_TRACE_ID
+        self.context.span.span_id = api_trace.INVALID_SPAN_ID
         carrier = {FORMAT.SINGLE_HEADER_KEY: "0-1-2-3-4-5-6-7"}
-        span_context = FORMAT.extract(get_as_list, carrier)
-        self.assertEqual(span_context.trace_id, api_trace.INVALID_TRACE_ID)
-        self.assertEqual(span_context.span_id, api_trace.INVALID_SPAN_ID)
+        FORMAT.extract(self.context, get_as_list, carrier)
+        self.assertEqual(self.context.span.trace_id,
+                         api_trace.INVALID_TRACE_ID)
+        self.assertEqual(self.context.span.span_id, api_trace.INVALID_SPAN_ID)
 
     def test_missing_trace_id(self):
         """If a trace id is missing, populate an invalid trace id."""
@@ -164,8 +167,9 @@ def test_missing_trace_id(self):
             FORMAT.SPAN_ID_KEY: self.serialized_span_id,
             FORMAT.FLAGS_KEY: "1"
         }
-        span_context = FORMAT.extract(get_as_list, carrier)
-        self.assertEqual(span_context.trace_id, api_trace.INVALID_TRACE_ID)
+        FORMAT.extract(self.context, get_as_list, carrier)
+        self.assertEqual(self.context.span.trace_id,
+                         api_trace.INVALID_TRACE_ID)
 
     def test_missing_span_id(self):
         """If a trace id is missing, populate an invalid trace id."""
@@ -173,5 +177,5 @@ def test_missing_span_id(self):
             FORMAT.TRACE_ID_KEY: self.serialized_trace_id,
             FORMAT.FLAGS_KEY: "1"
         }
-        span_context = FORMAT.extract(get_as_list, carrier)
-        self.assertEqual(span_context.span_id, api_trace.INVALID_SPAN_ID)
+        FORMAT.extract(self.context, get_as_list, carrier)
+        self.assertEqual(self.context.span.span_id, api_trace.INVALID_SPAN_ID)
diff --git a/opentelemetry-sdk/tests/trace/test_trace.py b/opentelemetry-sdk/tests/trace/test_trace.py
index 7a4faf78d11..7a91d23765e 100644
--- a/opentelemetry-sdk/tests/trace/test_trace.py
+++ b/opentelemetry-sdk/tests/trace/test_trace.py
@@ -114,74 +114,6 @@ def test_start_span_explicit(self):
             self.assertIs(tracer.get_current_span(), root)
             self.assertIsNotNone(child.end_time)
 
-    def test_span_members(self):
-        context = contextvars.ContextVar('test_span_members')
-        tracer = trace.Tracer(context)
-
-        other_context1 = trace_api.SpanContext(
-            trace_id=trace.generate_trace_id(),
-            span_id=trace.generate_span_id()
-        )
-        other_context2 = trace_api.SpanContext(
-            trace_id=trace.generate_trace_id(),
-            span_id=trace.generate_span_id()
-        )
-
-        self.assertIsNone(tracer.get_current_span())
-
-        with tracer.start_span('root') as root:
-            root.set_attribute('component', 'http')
-            root.set_attribute('http.method', 'GET')
-            root.set_attribute('http.url',
-                               'https://example.com:779/path/12/?q=d#123')
-            root.set_attribute('http.status_code', 200)
-            root.set_attribute('http.status_text', 'OK')
-            root.set_attribute('misc.pi', 3.14)
-
-            # Setting an attribute with the same key as an existing attribute
-            # SHOULD overwrite the existing attribute's value.
-            root.set_attribute('attr-key', 'attr-value1')
-            root.set_attribute('attr-key', 'attr-value2')
-
-            root.add_event('event0')
-            root.add_event('event1', {'name': 'birthday'})
-
-            root.add_link(other_context1)
-            root.add_link(other_context2, {'name': 'neighbor'})
-
-            # The public API does not expose getters.
-            # Checks by accessing the span members directly
-
-            self.assertEqual(len(root.attributes), 7)
-            self.assertEqual(root.attributes['component'], 'http')
-            self.assertEqual(root.attributes['http.method'], 'GET')
-            self.assertEqual(root.attributes['http.url'],
-                             'https://example.com:779/path/12/?q=d#123')
-            self.assertEqual(root.attributes['http.status_code'], 200)
-            self.assertEqual(root.attributes['http.status_text'], 'OK')
-            self.assertEqual(root.attributes['misc.pi'], 3.14)
-            self.assertEqual(root.attributes['attr-key'], 'attr-value2')
-
-            self.assertEqual(len(root.events), 2)
-            self.assertEqual(root.events[0],
-                             trace.Event(name='event0',
-                                         attributes={}))
-            self.assertEqual(root.events[1],
-                             trace.Event(name='event1',
-                                         attributes={'name': 'birthday'}))
-
-            self.assertEqual(len(root.links), 2)
-            self.assertEqual(root.links[0].context.trace_id,
-                             other_context1.trace_id)
-            self.assertEqual(root.links[0].context.span_id,
-                             other_context1.span_id)
-            self.assertEqual(root.links[0].attributes, {})
-            self.assertEqual(root.links[1].context.trace_id,
-                             other_context2.trace_id)
-            self.assertEqual(root.links[1].context.span_id,
-                             other_context2.span_id)
-            self.assertEqual(root.links[1].attributes, {'name': 'neighbor'})
-
 
 class TestSpan(unittest.TestCase):