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Posted to commits@samza.apache.org by ni...@apache.org on 2016/10/04 23:23:05 UTC

[5/5] samza git commit: SAMZA-914: Creating the fluent programming APIs w/ operators

SAMZA-914: Creating the fluent programming APIs w/ operators


Project: http://git-wip-us.apache.org/repos/asf/samza/repo
Commit: http://git-wip-us.apache.org/repos/asf/samza/commit/fbdd76da
Tree: http://git-wip-us.apache.org/repos/asf/samza/tree/fbdd76da
Diff: http://git-wip-us.apache.org/repos/asf/samza/diff/fbdd76da

Branch: refs/heads/samza-sql
Commit: fbdd76daada63e52575815737b9e5c1d4e787e71
Parents: f29c614
Author: Yi Pan (Data Infrastructure) <ni...@gmail.com>
Authored: Tue Oct 4 14:56:14 2016 -0700
Committer: Yi Pan (Data Infrastructure) <ni...@gmail.com>
Committed: Tue Oct 4 14:56:14 2016 -0700

----------------------------------------------------------------------
 build.gradle                                    |   6 +-
 gradle/dependency-versions.gradle               |   4 +-
 .../org/apache/samza/config/TestConfig.java     |   7 +-
 samza-operator/README.md                        |  17 +
 .../samza/operators/api/MessageStream.java      | 162 +++++++
 .../samza/operators/api/MessageStreams.java     |  80 ++++
 .../samza/operators/api/TriggerBuilder.java     | 314 +++++++++++++
 .../apache/samza/operators/api/WindowState.java |  77 +++
 .../org/apache/samza/operators/api/Windows.java | 195 ++++++++
 .../apache/samza/operators/api/data/Data.java   |  57 +++
 .../api/data/IncomingSystemMessage.java         |  76 +++
 .../operators/api/data/InputSystemMessage.java  |  43 ++
 .../samza/operators/api/data/LongOffset.java    |  75 +++
 .../samza/operators/api/data/Message.java       |  58 +++
 .../apache/samza/operators/api/data/Offset.java |  27 ++
 .../apache/samza/operators/api/data/Schema.java |  58 +++
 .../samza/operators/api/internal/Operators.java | 468 +++++++++++++++++++
 .../samza/operators/api/internal/Trigger.java   |  95 ++++
 .../samza/operators/api/internal/WindowFn.java  |  60 +++
 .../operators/api/internal/WindowOutput.java    |  55 +++
 .../samza/operators/impl/ChainedOperators.java  |  73 +++
 .../samza/operators/impl/OperatorImpl.java      |  92 ++++
 .../samza/operators/impl/ProcessorContext.java  |  53 +++
 .../operators/impl/SimpleOperatorImpl.java      |  49 ++
 .../samza/operators/impl/SinkOperatorImpl.java  |  41 ++
 .../samza/operators/impl/StateStoreImpl.java    |  56 +++
 .../operators/impl/data/avro/AvroData.java      | 262 +++++++++++
 .../operators/impl/data/avro/AvroSchema.java    | 296 ++++++++++++
 .../impl/data/serializers/SqlAvroSerde.java     | 108 +++++
 .../data/serializers/SqlAvroSerdeFactory.java   |  40 ++
 .../impl/data/serializers/SqlStringSerde.java   |  44 ++
 .../data/serializers/SqlStringSerdeFactory.java |  33 ++
 .../operators/impl/data/string/StringData.java  | 101 ++++
 .../impl/data/string/StringSchema.java          |  73 +++
 .../impl/window/SessionWindowImpl.java          |  66 +++
 .../samza/task/StreamOperatorAdaptorTask.java   |  85 ++++
 .../apache/samza/task/StreamOperatorTask.java   |  42 ++
 .../apache/samza/operators/api/TestMessage.java |  47 ++
 .../samza/operators/api/TestMessageStreams.java |  35 ++
 .../samza/operators/api/TestTriggerBuilder.java | 211 +++++++++
 .../apache/samza/operators/api/TestWindows.java | 106 +++++
 .../api/data/TestIncomingSystemMessage.java     |  53 +++
 .../operators/api/data/TestLongOffset.java      |  76 +++
 .../operators/api/internal/TestOperators.java   | 129 +++++
 .../operators/api/internal/TestTrigger.java     |  62 +++
 .../api/internal/TestWindowOutput.java          |  36 ++
 .../samza/operators/impl/TestOperatorImpl.java  |  70 +++
 .../samza/operators/impl/TestOutputMessage.java |  47 ++
 .../operators/impl/TestProcessorContext.java    |  40 ++
 .../operators/impl/TestSimpleOperatorImpl.java  |  54 +++
 .../operators/impl/TestSinkOperatorImpl.java    |  45 ++
 .../operators/impl/TestStateStoreImpl.java      |  69 +++
 .../impl/data/serializers/SqlAvroSerdeTest.java | 102 ++++
 .../impl/window/TestSessionWindowImpl.java      | 132 ++++++
 .../samza/task/BroadcastOperatorTask.java       | 110 +++++
 .../samza/task/InputJsonSystemMessage.java      |  63 +++
 .../org/apache/samza/task/JoinOperatorTask.java |  79 ++++
 .../task/TestStreamOperatorAdaptorTask.java     |  79 ++++
 .../samza/task/TestStreamOperatorTasks.java     | 105 +++++
 .../apache/samza/task/WindowOperatorTask.java   |  70 +++
 .../calcite/schema/TestAvroSchemaConverter.java |   3 +-
 samza-sql-core/README.md                        |  17 -
 .../org/apache/samza/sql/api/data/Data.java     |  54 ---
 .../apache/samza/sql/api/data/EntityName.java   | 140 ------
 .../org/apache/samza/sql/api/data/Relation.java |  40 --
 .../org/apache/samza/sql/api/data/Schema.java   |  55 ---
 .../org/apache/samza/sql/api/data/Stream.java   |  40 --
 .../org/apache/samza/sql/api/data/Table.java    |  38 --
 .../org/apache/samza/sql/api/data/Tuple.java    |  75 ---
 .../samza/sql/api/operators/Operator.java       |  73 ---
 .../sql/api/operators/OperatorCallback.java     |  70 ---
 .../samza/sql/api/operators/OperatorRouter.java |  54 ---
 .../samza/sql/api/operators/OperatorSpec.java   |  58 ---
 .../samza/sql/api/operators/SimpleOperator.java |  34 --
 .../sql/api/operators/SqlOperatorFactory.java   |  37 --
 .../samza/sql/data/IncomingMessageTuple.java    |  94 ----
 .../apache/samza/sql/data/avro/AvroData.java    | 262 -----------
 .../apache/samza/sql/data/avro/AvroSchema.java  | 296 ------------
 .../sql/data/serializers/SqlAvroSerde.java      | 109 -----
 .../data/serializers/SqlAvroSerdeFactory.java   |  40 --
 .../sql/data/serializers/SqlStringSerde.java    |  45 --
 .../data/serializers/SqlStringSerdeFactory.java |  33 --
 .../samza/sql/data/string/StringData.java       | 101 ----
 .../samza/sql/data/string/StringSchema.java     |  73 ---
 .../operators/factory/NoopOperatorCallback.java |  50 --
 .../factory/SimpleOperatorFactoryImpl.java      |  51 --
 .../operators/factory/SimpleOperatorImpl.java   | 136 ------
 .../operators/factory/SimpleOperatorSpec.java   | 106 -----
 .../sql/operators/factory/SimpleRouter.java     | 136 ------
 .../sql/operators/join/StreamStreamJoin.java    | 117 -----
 .../operators/join/StreamStreamJoinSpec.java    |  38 --
 .../sql/operators/partition/PartitionOp.java    | 120 -----
 .../sql/operators/partition/PartitionSpec.java  |  91 ----
 .../sql/operators/window/BoundedTimeWindow.java | 161 -------
 .../samza/sql/operators/window/WindowSpec.java  |  67 ---
 .../samza/sql/operators/window/WindowState.java |  44 --
 .../sql/window/storage/OrderedStoreKey.java     |  26 --
 .../org/apache/samza/system/sql/LongOffset.java |  66 ---
 .../org/apache/samza/system/sql/Offset.java     |  27 --
 .../samza/task/sql/RouterMessageCollector.java  |  56 ---
 .../samza/task/sql/SimpleMessageCollector.java  | 114 -----
 .../sql/data/serializers/SqlAvroSerdeTest.java  | 102 ----
 .../task/sql/RandomWindowOperatorTask.java      |  96 ----
 .../apache/samza/task/sql/StreamSqlTask.java    | 104 -----
 .../samza/task/sql/UserCallbacksSqlTask.java    | 150 ------
 settings.gradle                                 |   2 +-
 106 files changed, 5265 insertions(+), 3704 deletions(-)
----------------------------------------------------------------------


http://git-wip-us.apache.org/repos/asf/samza/blob/fbdd76da/build.gradle
----------------------------------------------------------------------
diff --git a/build.gradle b/build.gradle
index 8fe4c46..aeefd1c 100644
--- a/build.gradle
+++ b/build.gradle
@@ -336,7 +336,7 @@ project(":samza-yarn_$scalaVersion") {
 }
 
 if (JavaVersion.current().isJava8Compatible()) {
-  project(":samza-sql-core") {
+  project(":samza-operator") {
     apply plugin: 'java'
     
     sourceCompatibility = 1.8
@@ -345,7 +345,9 @@ if (JavaVersion.current().isJava8Compatible()) {
       compile project(':samza-api')
       compile project(":samza-core_$scalaVersion")
       compile "commons-collections:commons-collections:$commonsCollectionVersion"
+      compile "org.apache.commons:commons-lang3:$commonsLang3Version"
       compile "org.apache.avro:avro:$avroVersion"
+      compile "org.reactivestreams:reactive-streams:$reactiveStreamVersion"
       testCompile "junit:junit:$junitVersion"
       testCompile "org.mockito:mockito-all:$mockitoVersion"
     }
@@ -363,7 +365,7 @@ if (JavaVersion.current().isJava8Compatible()) {
     sourceCompatibility = 1.8
 
     dependencies {
-      compile project(":samza-sql-core")
+      compile project(":samza-operator")
       compile "org.apache.calcite:calcite-core:$calciteVersion"
       testCompile "junit:junit:$junitVersion"
       testCompile "org.mockito:mockito-all:$mockitoVersion"

http://git-wip-us.apache.org/repos/asf/samza/blob/fbdd76da/gradle/dependency-versions.gradle
----------------------------------------------------------------------
diff --git a/gradle/dependency-versions.gradle b/gradle/dependency-versions.gradle
index c52960c..845a3fd 100644
--- a/gradle/dependency-versions.gradle
+++ b/gradle/dependency-versions.gradle
@@ -36,7 +36,9 @@
   guavaVersion = "17.0"
   commonsCodecVersion = "1.9"
   commonsCollectionVersion = "3.2.1"
-  avroVersion = "1.7.7"
+  avroVersion = "1.4.0"
   calciteVersion = "1.2.0-incubating"
   httpClientVersion="4.4.1"
+  reactiveStreamVersion="1.0.0"
+  commonsLang3Version="3.4"
 }

http://git-wip-us.apache.org/repos/asf/samza/blob/fbdd76da/samza-api/src/test/java/org/apache/samza/config/TestConfig.java
----------------------------------------------------------------------
diff --git a/samza-api/src/test/java/org/apache/samza/config/TestConfig.java b/samza-api/src/test/java/org/apache/samza/config/TestConfig.java
index 5d066c5..7d9d56c 100644
--- a/samza-api/src/test/java/org/apache/samza/config/TestConfig.java
+++ b/samza-api/src/test/java/org/apache/samza/config/TestConfig.java
@@ -19,12 +19,13 @@
 
 package org.apache.samza.config;
 
-import static org.junit.Assert.*;
+import org.junit.Test;
 
-import java.util.Map;
 import java.util.HashMap;
+import java.util.Map;
 
-import org.junit.Test;
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
 
 public class TestConfig {
   /**

http://git-wip-us.apache.org/repos/asf/samza/blob/fbdd76da/samza-operator/README.md
----------------------------------------------------------------------
diff --git a/samza-operator/README.md b/samza-operator/README.md
new file mode 100644
index 0000000..15d2092
--- /dev/null
+++ b/samza-operator/README.md
@@ -0,0 +1,17 @@
+<!--
+   Licensed to the Apache Software Foundation (ASF) under one or more
+   contributor license agreements.  See the NOTICE file distributed with
+   this work for additional information regarding copyright ownership.
+   The ASF licenses this file to You 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.
+-->
+samza-operator is an experimental module that is under development (SAMZA-552).

http://git-wip-us.apache.org/repos/asf/samza/blob/fbdd76da/samza-operator/src/main/java/org/apache/samza/operators/api/MessageStream.java
----------------------------------------------------------------------
diff --git a/samza-operator/src/main/java/org/apache/samza/operators/api/MessageStream.java b/samza-operator/src/main/java/org/apache/samza/operators/api/MessageStream.java
new file mode 100644
index 0000000..a01cee9
--- /dev/null
+++ b/samza-operator/src/main/java/org/apache/samza/operators/api/MessageStream.java
@@ -0,0 +1,162 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you 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.
+ */
+
+package org.apache.samza.operators.api;
+
+import org.apache.samza.operators.api.data.Message;
+import org.apache.samza.operators.api.internal.WindowOutput;
+import org.apache.samza.operators.api.internal.Operators;
+import org.apache.samza.operators.api.Windows.Window;
+import org.apache.samza.system.SystemStream;
+import org.apache.samza.task.MessageCollector;
+import org.apache.samza.task.TaskCoordinator;
+
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.function.BiFunction;
+import java.util.function.Function;
+
+
+/**
+ * This class defines either the input or output streams to/from the operators. Users use the API methods defined here to
+ * directly program the stream processing stages that processes a stream and generate another one.
+ *
+ * @param <M>  Type of message in this stream
+ */
+public class MessageStream<M extends Message> {
+
+  /**
+   * Public API methods start here
+   */
+
+  /**
+   * Defines a function API that takes three input parameters w/ types {@code A}, {@code B}, and {@code C} and w/o a return value
+   *
+   * @param <A>  the type of input {@code a}
+   * @param <B>  the type of input {@code b}
+   * @param <C>  the type of input {@code c}
+   */
+  @FunctionalInterface
+  public interface VoidFunction3 <A, B, C> {
+    public void apply(A a, B b, C c);
+  }
+
+  /**
+   * Method to apply a map function (1:1) on a {@link MessageStream}
+   *
+   * @param mapper  the mapper function to map one input {@link Message} to one output {@link Message}
+   * @param <OM>  the type of the output {@link Message} in the output {@link MessageStream}
+   * @return the output {@link MessageStream} by applying the map function on the input {@link MessageStream}
+   */
+  public <OM extends Message> MessageStream<OM> map(Function<M, OM> mapper) {
+    return Operators.<M, OM>getStreamOperator(m -> new ArrayList<OM>() {{
+      OM r = mapper.apply(m);
+      if (r != null) {
+        this.add(r);
+      }
+    }}).getOutputStream();
+  }
+
+  /**
+   * Method to apply a flatMap function (1:n) on a {@link MessageStream}
+   *
+   * @param flatMapper  the flat mapper function to map one input {@link Message} to zero or more output {@link Message}s
+   * @param <OM>  the type of the output {@link Message} in the output {@link MessageStream}
+   * @return the output {@link MessageStream} by applying the map function on the input {@link MessageStream}
+   */
+  public <OM extends Message> MessageStream<OM> flatMap(Function<M, Collection<OM>> flatMapper) {
+    return Operators.getStreamOperator(flatMapper).getOutputStream();
+  }
+
+  /**
+   * Method to apply a filter function on a {@link MessageStream}
+   *
+   * @param filter  the filter function to filter input {@link Message}s from the input {@link MessageStream}
+   * @return the output {@link MessageStream} after applying the filter function on the input {@link MessageStream}
+   */
+  public MessageStream<M> filter(Function<M, Boolean> filter) {
+    return Operators.<M, M>getStreamOperator(t -> new ArrayList<M>() {{
+      if (filter.apply(t)) {
+        this.add(t);
+      }
+    }}).getOutputStream();
+  }
+
+  /**
+   * Method to send an input {@link MessageStream} to an output {@link SystemStream}, and allows the output {@link MessageStream}
+   * to be consumed by downstream stream operators again.
+   *
+   * @param sink  the user-defined sink function to send the input {@link Message}s to the external output systems
+   */
+  public void sink(VoidFunction3<M, MessageCollector, TaskCoordinator> sink) {
+    Operators.getSinkOperator(sink);
+  }
+
+  /**
+   * Method to perform a window function (i.e. a group-by, aggregate function) on a {@link MessageStream}
+   *
+   * @param window  the window function to group and aggregate the input {@link Message}s from the input {@link MessageStream}
+   * @param <WK>  the type of key in the output {@link Message} from the {@link Window} function
+   * @param <WV>  the type of output value from
+   * @param <WS>  the type of window state kept in the {@link Window} function
+   * @param <WM>  the type of {@link WindowOutput} message from the {@link Window} function
+   * @return the output {@link MessageStream} after applying the window function on the input {@link MessageStream}
+   */
+  public <WK, WV, WS extends WindowState<WV>, WM extends WindowOutput<WK, WV>> MessageStream<WM> window(Window<M, WK, WV, WM> window) {
+    return Operators.getWindowOperator(Windows.getInternalWindowFn(window)).getOutputStream();
+  }
+
+  /**
+   * Method to add an input {@link MessageStream} to a join function. Note that we currently only support 2-way joins.
+   *
+   * @param other  the other stream to be joined w/
+   * @param merger  the common function to merge messages from this {@link MessageStream} and {@code other}
+   * @param <K>  the type of join key
+   * @param <JM>  the type of message in the {@link Message} from the other join stream
+   * @param <RM>  the type of message in the {@link Message} from the join function
+   * @return the output {@link MessageStream} from the join function {@code joiner}
+   */
+  public <K, JM extends Message<K, ?>, RM extends Message> MessageStream<RM> join(MessageStream<JM> other,
+      BiFunction<M, JM, RM> merger) {
+    MessageStream<RM> outputStream = new MessageStream<>();
+
+    BiFunction<M, JM, RM> parJoin1 = merger::apply;
+    BiFunction<JM, M, RM> parJoin2 = (m, t1) -> merger.apply(t1, m);
+
+    // TODO: need to add default store functions for the two partial join functions
+
+    Operators.<JM, K, M, RM>getPartialJoinOperator(parJoin2, outputStream);
+    Operators.<M, K, JM, RM>getPartialJoinOperator(parJoin1, outputStream);
+    return outputStream;
+  }
+
+  /**
+   * Method to merge all {@code others} streams w/ this {@link MessageStream}. The merging streams must have the same type {@code M}
+   *
+   * @param others  other streams to be merged w/ this one
+   * @return  the merged output stream
+   */
+  public MessageStream<M> merge(Collection<MessageStream<M>> others) {
+    MessageStream<M> outputStream = new MessageStream<>();
+
+    others.add(this);
+    others.forEach(other -> Operators.getMergeOperator(outputStream));
+    return outputStream;
+  }
+}

http://git-wip-us.apache.org/repos/asf/samza/blob/fbdd76da/samza-operator/src/main/java/org/apache/samza/operators/api/MessageStreams.java
----------------------------------------------------------------------
diff --git a/samza-operator/src/main/java/org/apache/samza/operators/api/MessageStreams.java b/samza-operator/src/main/java/org/apache/samza/operators/api/MessageStreams.java
new file mode 100644
index 0000000..59dd91c
--- /dev/null
+++ b/samza-operator/src/main/java/org/apache/samza/operators/api/MessageStreams.java
@@ -0,0 +1,80 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you 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.
+ */
+package org.apache.samza.operators.api;
+
+import org.apache.samza.operators.api.data.IncomingSystemMessage;
+import org.apache.samza.system.SystemStreamPartition;
+
+
+/**
+ * This class defines all methods to create a {@link MessageStream} object. Users can use this to create an {@link MessageStream}
+ * from a specific input source.
+ *
+ */
+
+public final class MessageStreams {
+
+  /**
+   * private constructor to prevent instantiation
+   */
+  private MessageStreams() {}
+
+  /**
+   * private class for system input/output {@link MessageStream}
+   */
+  public static final class SystemMessageStream extends MessageStream<IncomingSystemMessage> {
+    /**
+     * The corresponding {@link org.apache.samza.system.SystemStream}
+     */
+    private final SystemStreamPartition ssp;
+
+    /**
+     * Constructor for input system stream
+     *
+     * @param ssp  the input {@link SystemStreamPartition} for the input {@link SystemMessageStream}
+     */
+    private SystemMessageStream(SystemStreamPartition ssp) {
+      this.ssp = ssp;
+    }
+
+    /**
+     * Getter for the {@link SystemStreamPartition} of the input
+     *
+     * @return the input {@link SystemStreamPartition}
+     */
+    public SystemStreamPartition getSystemStreamPartition() {
+      return this.ssp;
+    }
+  }
+
+  /**
+   * Public static API methods start here
+   */
+
+  /**
+   * Static API method to create a {@link MessageStream} from a system input stream
+   *
+   * @param ssp  the input {@link SystemStreamPartition}
+   * @return the {@link MessageStream} object takes {@code ssp} as the input
+   */
+  public static SystemMessageStream input(SystemStreamPartition ssp) {
+    return new SystemMessageStream(ssp);
+  }
+
+}

http://git-wip-us.apache.org/repos/asf/samza/blob/fbdd76da/samza-operator/src/main/java/org/apache/samza/operators/api/TriggerBuilder.java
----------------------------------------------------------------------
diff --git a/samza-operator/src/main/java/org/apache/samza/operators/api/TriggerBuilder.java b/samza-operator/src/main/java/org/apache/samza/operators/api/TriggerBuilder.java
new file mode 100644
index 0000000..fc3ea37
--- /dev/null
+++ b/samza-operator/src/main/java/org/apache/samza/operators/api/TriggerBuilder.java
@@ -0,0 +1,314 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you 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.
+ */
+package org.apache.samza.operators.api;
+
+import org.apache.samza.operators.api.data.Message;
+import org.apache.samza.operators.api.internal.Trigger;
+
+import java.util.concurrent.TimeUnit;
+import java.util.function.BiFunction;
+import java.util.function.Function;
+
+
+/**
+ * This class defines a builder of {@link Trigger} object for a {@link Windows.Window}. The triggers are categorized into
+ * three types:
+ *
+ * <p>
+ *   early trigger: defines the condition when the first output from the window function is sent.
+ *   late trigger: defines the condition when the updated output after the first output is sent.
+ *   timer trigger: defines a system timeout condition to trigger output if no more inputs are received to enable early/late triggers
+ * </p>
+ *
+ * If multiple conditions are defined for a specific type of trigger, the aggregated trigger is the disjunction of the each individual trigger (i.e. OR).
+ *
+ * NOTE: Programmers should not use classes defined in {@link org.apache.samza.operators.api.internal} to create triggers
+ *
+ *
+ * @param <M>  the type of input {@link Message} to the {@link Windows.Window}
+ * @param <V>  the type of output value from the {@link Windows.Window}
+ */
+public final class TriggerBuilder<M extends Message, V> {
+
+  /**
+   * Predicate helper to OR multiple trigger conditions
+   */
+  static class PredicateHelper {
+    static <M, S> BiFunction<M, S, Boolean> or(BiFunction<M, S, Boolean> lhs, BiFunction<M, S, Boolean> rhs) {
+      return (m, s) -> lhs.apply(m, s) || rhs.apply(m, s);
+    }
+
+    static <S> Function<S, Boolean> or(Function<S, Boolean> lhs, Function<S, Boolean> rhs) {
+      return s -> lhs.apply(s) || rhs.apply(s);
+    }
+  }
+
+  /**
+   * The early trigger condition that determines the first output from the {@link Windows.Window}
+   */
+  private BiFunction<M, WindowState<V>, Boolean> earlyTrigger = null;
+
+  /**
+   * The late trigger condition that determines the late output(s) from the {@link Windows.Window}
+   */
+  private BiFunction<M, WindowState<V>, Boolean> lateTrigger = null;
+
+  /**
+   * The system timer based trigger conditions that guarantees the {@link Windows.Window} proceeds forward
+   */
+  private Function<WindowState<V>, Boolean> timerTrigger = null;
+
+  /**
+   * The state updater function to be applied after the first output is triggered
+   */
+  private Function<WindowState<V>, WindowState<V>> earlyTriggerUpdater = Function.identity();
+
+  /**
+   * The state updater function to be applied after the late output is triggered
+   */
+  private Function<WindowState<V>, WindowState<V>> lateTriggerUpdater = Function.identity();
+
+  /**
+   * Helper method to add a trigger condition
+   *
+   * @param currentTrigger  current trigger condition
+   * @param newTrigger  new trigger condition
+   * @return  combined trigger condition that is {@code currentTrigger} OR {@code newTrigger}
+   */
+  private BiFunction<M, WindowState<V>, Boolean> addTrigger(BiFunction<M, WindowState<V>, Boolean> currentTrigger,
+      BiFunction<M, WindowState<V>, Boolean> newTrigger) {
+    if (currentTrigger == null) {
+      return newTrigger;
+    }
+
+    return PredicateHelper.or(currentTrigger, newTrigger);
+  }
+
+  /**
+   * Helper method to add a system timer trigger
+   *
+   * @param currentTimer  current timer condition
+   * @param newTimer  new timer condition
+   * @return  combined timer condition that is {@code currentTimer} OR {@code newTimer}
+   */
+  private Function<WindowState<V>, Boolean> addTimerTrigger(Function<WindowState<V>, Boolean> currentTimer,
+      Function<WindowState<V>, Boolean> newTimer) {
+    if (currentTimer == null) {
+      return newTimer;
+    }
+
+    return PredicateHelper.or(currentTimer, newTimer);
+  }
+
+  /**
+   * default constructor to prevent instantiation
+   */
+  private TriggerBuilder() {}
+
+  /**
+   * Constructor that set the size limit as the early trigger for a window
+   *
+   * @param sizeLimit  the number of messages in a window that would trigger the first output
+   */
+  private TriggerBuilder(long sizeLimit) {
+    this.earlyTrigger = (m, s) -> s.getNumberMessages() > sizeLimit;
+  }
+
+  /**
+   * Constructor that set the event time length as the early trigger
+   *
+   * @param eventTimeFunction  the function that calculate the event time in nano-second from the input {@link Message}
+   * @param wndLenMs  the window length in event time in milli-second
+   */
+  private TriggerBuilder(Function<M, Long> eventTimeFunction, long wndLenMs) {
+    this.earlyTrigger = (m, s) ->
+        TimeUnit.NANOSECONDS.toMillis(Math.max(s.getLatestEventTimeNs() - s.getEarliestEventTimeNs(),
+            eventTimeFunction.apply(m) - s.getEarliestEventTimeNs())) > wndLenMs;
+  }
+
+  /**
+   * Constructor that set the special token message as the early trigger
+   *
+   * @param tokenFunc  the function that checks whether an input {@link Message} is a token message that triggers window output
+   */
+  private TriggerBuilder(Function<M, Boolean> tokenFunc) {
+    this.earlyTrigger = (m, s) -> tokenFunc.apply(m);
+  }
+
+  /**
+   * Build method that creates an {@link Trigger} object based on the trigger conditions set in {@link TriggerBuilder}
+   * This is kept package private and only used by {@link Windows} to convert the mutable {@link TriggerBuilder} object to an immutable {@link Trigger} object
+   *
+   * @return  the final {@link Trigger} object
+   */
+  Trigger<M, WindowState<V>> build() {
+    return Trigger.createTrigger(this.timerTrigger, this.earlyTrigger, this.lateTrigger, this.earlyTriggerUpdater, this.lateTriggerUpdater);
+  }
+
+  /**
+   * Public API methods start here
+   */
+
+
+  /**
+   * API method to allow users to set an update method to update the output value after the first window output is triggered
+   * by the early trigger condition
+   *
+   * @param onTriggerFunc  the method to update the output value after the early trigger
+   * @return  the {@link TriggerBuilder} object
+   */
+  public TriggerBuilder<M, V> onEarlyTrigger(Function<V, V> onTriggerFunc) {
+    this.earlyTriggerUpdater = s -> { s.setOutputValue(onTriggerFunc.apply(s.getOutputValue())); return s; };
+    return this;
+  }
+
+  /**
+   * API method to allow users to set an update method to update the output value after a late window output is triggered
+   * by the late trigger condition
+   *
+   * @param onTriggerFunc  the method to update the output value after the late trigger
+   * @return  the {@link TriggerBuilder} object
+   */
+  public TriggerBuilder<M, V> onLateTrigger(Function<V, V> onTriggerFunc) {
+    this.lateTriggerUpdater = s -> { s.setOutputValue(onTriggerFunc.apply(s.getOutputValue())); return s; };
+    return this;
+  }
+
+  /**
+   * API method to allow users to add a system timer trigger based on timeout after the last message received in the window
+   *
+   * @param timeoutMs  the timeout in ms after the last message received in the window
+   * @return  the {@link TriggerBuilder} object
+   */
+  public TriggerBuilder<M, V> addTimeoutSinceLastMessage(long timeoutMs) {
+    this.timerTrigger = this.addTimerTrigger(this.timerTrigger,
+        s -> TimeUnit.NANOSECONDS.toMillis(s.getLastMessageTimeNs()) + timeoutMs < System.currentTimeMillis());
+    return this;
+  }
+
+  /**
+   * API method to allow users to add a system timer trigger based on the timeout after the first message received in the window
+   *
+   * @param timeoutMs  the timeout in ms after the first message received in the window
+   * @return  the {@link TriggerBuilder} object
+   */
+  public TriggerBuilder<M, V> addTimeoutSinceFirstMessage(long timeoutMs) {
+    this.timerTrigger = this.addTimerTrigger(this.timerTrigger, s ->
+        TimeUnit.NANOSECONDS.toMillis(s.getFirstMessageTimeNs()) + timeoutMs < System.currentTimeMillis());
+    return this;
+  }
+
+  /**
+   * API method allow users to add a late trigger based on the window size limit
+   *
+   * @param sizeLimit  limit on the number of messages in window
+   * @return  the {@link TriggerBuilder} object
+   */
+  public TriggerBuilder<M, V> addLateTriggerOnSizeLimit(long sizeLimit) {
+    this.lateTrigger = this.addTrigger(this.lateTrigger, (m, s) -> s.getNumberMessages() > sizeLimit);
+    return this;
+  }
+
+  /**
+   * API method to allow users to define a customized late trigger function based on input message and the window state
+   *
+   * @param lateTrigger  the late trigger condition based on input {@link Message} and the current {@link WindowState}
+   * @return  the {@link TriggerBuilder} object
+   */
+  public TriggerBuilder<M, V> addLateTrigger(BiFunction<M, WindowState<V>, Boolean> lateTrigger) {
+    this.lateTrigger = this.addTrigger(this.lateTrigger, lateTrigger);
+    return this;
+  }
+
+  /**
+   * Static API method to create a {@link TriggerBuilder} w/ early trigger condition based on window size limit
+   *
+   * @param sizeLimit  window size limit
+   * @param <M>  the type of input {@link Message}
+   * @param <V>  the type of {@link Windows.Window} output value
+   * @return  the {@link TriggerBuilder} object
+   */
+  public static <M extends Message, V> TriggerBuilder<M, V> earlyTriggerWhenExceedWndLen(long sizeLimit) {
+    return new TriggerBuilder<M, V>(sizeLimit);
+  }
+
+  /**
+   * Static API method to create a {@link TriggerBuilder} w/ early trigger condition based on event time window
+   *
+   *
+   * @param eventTimeFunc  the function to get the event time from the input message
+   * @param eventTimeWndSizeMs  the event time window size in Ms
+   * @param <M>  the type of input {@link Message}
+   * @param <V>  the type of {@link Windows.Window} output value
+   * @return  the {@link TriggerBuilder} object
+   */
+  public static <M extends Message, V> TriggerBuilder<M, V> earlyTriggerOnEventTime(Function<M, Long> eventTimeFunc, long eventTimeWndSizeMs) {
+    return new TriggerBuilder<M, V>(eventTimeFunc, eventTimeWndSizeMs);
+  }
+
+  /**
+   * Static API method to create a {@link TriggerBuilder} w/ early trigger condition based on token messages
+   *
+   * @param tokenFunc  the function to determine whether an input message is a window token or not
+   * @param <M>  the type of input {@link Message}
+   * @param <V>  the type of {@link Windows.Window} output value
+   * @return  the {@link TriggerBuilder} object
+   */
+  public static <M extends Message, V> TriggerBuilder<M, V> earlyTriggerOnTokenMsg(Function<M, Boolean> tokenFunc) {
+    return new TriggerBuilder<M, V>(tokenFunc);
+  }
+
+  /**
+   * Static API method to allow customized early trigger condition based on input {@link Message} and the corresponding {@link WindowState}
+   *
+   * @param earlyTrigger  the user defined early trigger condition
+   * @param <M>   the input message type
+   * @param <V>   the output value from the window
+   * @return   the {@link TriggerBuilder} object
+   */
+  public static <M extends Message, V> TriggerBuilder<M, V> earlyTrigger(BiFunction<M, WindowState<V>, Boolean> earlyTrigger) {
+    TriggerBuilder<M, V> newTriggers =  new TriggerBuilder<M, V>();
+    newTriggers.earlyTrigger = newTriggers.addTrigger(newTriggers.earlyTrigger, earlyTrigger);
+    return newTriggers;
+  }
+
+  /**
+   * Static API method to create a {@link TriggerBuilder} w/ system timeout after the last message received in the window
+   *
+   * @param timeoutMs  timeout in ms after the last message received
+   * @param <M>  the type of input {@link Message}
+   * @param <V>  the type of {@link Windows.Window} output value
+   * @return  the {@link TriggerBuilder} object
+   */
+  public static <M extends Message, V> TriggerBuilder<M, V> timeoutSinceLastMessage(long timeoutMs) {
+    return new TriggerBuilder<M, V>().addTimeoutSinceLastMessage(timeoutMs);
+  }
+
+  /**
+   * Static API method to create a {@link TriggerBuilder} w/ system timeout after the first message received in the window
+   *
+   * @param timeoutMs  timeout in ms after the first message received
+   * @param <M>  the type of input {@link Message}
+   * @param <V>  the type of {@link Windows.Window} output value
+   * @return  the {@link TriggerBuilder} object
+   */
+  public static <M extends Message, V> TriggerBuilder<M, V> timeoutSinceFirstMessage(long timeoutMs) {
+    return new TriggerBuilder<M, V>().addTimeoutSinceFirstMessage(timeoutMs);
+  }
+}

http://git-wip-us.apache.org/repos/asf/samza/blob/fbdd76da/samza-operator/src/main/java/org/apache/samza/operators/api/WindowState.java
----------------------------------------------------------------------
diff --git a/samza-operator/src/main/java/org/apache/samza/operators/api/WindowState.java b/samza-operator/src/main/java/org/apache/samza/operators/api/WindowState.java
new file mode 100644
index 0000000..402cc42
--- /dev/null
+++ b/samza-operator/src/main/java/org/apache/samza/operators/api/WindowState.java
@@ -0,0 +1,77 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you 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.
+ */
+package org.apache.samza.operators.api;
+
+/**
+ * This interface defines the methods a window state class has to implement. The programmers are allowed to implement
+ * customized window state to be stored in window state stores by implementing this interface class.
+ *
+ * @param <WV>  the type for window output value
+ */
+public interface WindowState<WV> {
+  /**
+   * Method to get the system time when the first message in the window is received
+   *
+   * @return  nano-second of system time for the first message received in the window
+   */
+  long getFirstMessageTimeNs();
+
+  /**
+   * Method to get the system time when the last message in the window is received
+   *
+   * @return  nano-second of system time for the last message received in the window
+   */
+  long getLastMessageTimeNs();
+
+  /**
+   * Method to get the earliest event time in the window
+   *
+   * @return  the earliest event time in nano-second in the window
+   */
+  long getEarliestEventTimeNs();
+
+  /**
+   * Method to get the latest event time in the window
+   *
+   * @return  the latest event time in nano-second in the window
+   */
+  long getLatestEventTimeNs();
+
+  /**
+   * Method to get the total number of messages received in the window
+   *
+   * @return  number of messages in the window
+   */
+  long getNumberMessages();
+
+  /**
+   * Method to get the corresponding window's output value
+   *
+   * @return  the corresponding window's output value
+   */
+  WV getOutputValue();
+
+  /**
+   * Method to set the corresponding window's output value
+   *
+   * @param value  the corresponding window's output value
+   */
+  void setOutputValue(WV value);
+
+}

http://git-wip-us.apache.org/repos/asf/samza/blob/fbdd76da/samza-operator/src/main/java/org/apache/samza/operators/api/Windows.java
----------------------------------------------------------------------
diff --git a/samza-operator/src/main/java/org/apache/samza/operators/api/Windows.java b/samza-operator/src/main/java/org/apache/samza/operators/api/Windows.java
new file mode 100644
index 0000000..e557b34
--- /dev/null
+++ b/samza-operator/src/main/java/org/apache/samza/operators/api/Windows.java
@@ -0,0 +1,195 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you 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.
+ */
+package org.apache.samza.operators.api;
+
+import org.apache.samza.operators.api.data.Message;
+import org.apache.samza.operators.api.internal.WindowOutput;
+import org.apache.samza.operators.api.internal.Trigger;
+import org.apache.samza.operators.api.internal.Operators;
+import org.apache.samza.operators.api.internal.WindowFn;
+import org.apache.samza.storage.kv.Entry;
+
+import java.util.Collection;
+import java.util.function.BiFunction;
+import java.util.function.Function;
+
+
+/**
+ * This class defines a collection of {@link Window} functions. The public classes and methods here are intended to be
+ * used by the user (i.e. programmers) to create {@link Window} function directly.
+ *
+ */
+public final class Windows {
+
+  /**
+   * private constructor to prevent instantiation
+   */
+  private Windows() {}
+
+  /**
+   * This class defines a session window function class
+   *
+   * @param <M>  the type of input {@link Message}
+   * @param <WK>  the type of session key in the session window
+   * @param <WV>  the type of output value in each session window
+   */
+  static class SessionWindow<M extends Message, WK, WV> implements Window<M, WK, WV, WindowOutput<WK, WV>> {
+
+    /**
+     * Constructor. Made private s.t. it can only be instantiated via the static API methods in {@link Windows}
+     *
+     * @param sessionKeyFunction  function to get the session key from the input {@link Message}
+     * @param aggregator  function to calculate the output value based on the input {@link Message} and current output value
+     */
+    private SessionWindow(Function<M, WK> sessionKeyFunction, BiFunction<M, WV, WV> aggregator) {
+      this.wndKeyFunction = sessionKeyFunction;
+      this.aggregator = aggregator;
+    }
+
+    /**
+     * function to calculate the window key from input message
+     */
+    private final Function<M, WK> wndKeyFunction;
+
+    /**
+     * function to calculate the output value from the input message and the current output value
+     */
+    private final BiFunction<M, WV, WV> aggregator;
+
+    /**
+     * trigger condition that determines when to send out the output value in a {@link WindowOutput} message
+     */
+    private Trigger<M, WindowState<WV>> trigger = null;
+
+    //TODO: need to create a set of {@link StoreFunctions} that is default to input {@link Message} type for {@link Window}
+    private Operators.StoreFunctions<M, WK, WindowState<WV>> storeFunctions = null;
+
+    /**
+     * Public API methods start here
+     */
+
+    /**
+     * Public API method to define the watermark trigger for the window operator
+     *
+     * @param wndTrigger {@link Trigger} function defines the watermark trigger for this {@link SessionWindow}
+     * @return The window operator w/ the defined watermark trigger
+     */
+    @Override
+    public Window<M, WK, WV, WindowOutput<WK, WV>> setTriggers(TriggerBuilder<M, WV> wndTrigger) {
+      this.trigger = wndTrigger.build();
+      return this;
+    }
+
+    private BiFunction<M, Entry<WK, WindowState<WV>>, WindowOutput<WK, WV>> getTransformFunc() {
+      // TODO: actual implementation of the main session window logic, based on the wndKeyFunction, aggregator, and triggers;
+      return null;
+    }
+
+    private WindowFn<M, WK, WindowState<WV>, WindowOutput<WK, WV>> getInternalWindowFn() {
+      return new WindowFn<M, WK, WindowState<WV>, WindowOutput<WK, WV>>() {
+
+        @Override public BiFunction<M, Entry<WK, WindowState<WV>>, WindowOutput<WK, WV>> getTransformFunc() {
+          return SessionWindow.this.getTransformFunc();
+        }
+
+        @Override public Operators.StoreFunctions<M, WK, WindowState<WV>> getStoreFuncs() {
+          return SessionWindow.this.storeFunctions;
+        }
+
+        @Override public Trigger<M, WindowState<WV>> getTrigger() {
+          return SessionWindow.this.trigger;
+        }
+      };
+    }
+  }
+
+  static <M extends Message, WK, WV, WS extends WindowState<WV>, WM extends WindowOutput<WK, WV>> WindowFn<M, WK, WS, WM> getInternalWindowFn(
+      Window<M, WK, WV, WM> window) {
+    if (window instanceof SessionWindow) {
+      SessionWindow<M, WK, WV> sessionWindow = (SessionWindow<M, WK, WV>) window;
+      return (WindowFn<M, WK, WS, WM>) sessionWindow.getInternalWindowFn();
+    }
+    throw new IllegalArgumentException("Input window type not supported.");
+  }
+
+  /**
+   * Public static API methods start here
+   *
+   */
+
+  /**
+   * The public programming interface class for window function
+   *
+   * @param <M>  the type of input {@link Message}
+   * @param <WK>  the type of key to the {@link Window}
+   * @param <WV>  the type of output value in the {@link WindowOutput}
+   * @param <WM>  the type of message in the window output stream
+   */
+  public interface Window<M extends Message, WK, WV, WM extends WindowOutput<WK, WV>> {
+
+    /**
+     * Set the triggers for this {@link Window}
+     *
+     * @param wndTrigger  trigger conditions set by the programmers
+     * @return  the {@link Window} function w/ the trigger {@code wndTrigger}
+     */
+    Window<M, WK, WV, WM> setTriggers(TriggerBuilder<M, WV> wndTrigger);
+  }
+
+  /**
+   * Static API method to create a {@link SessionWindow} in which the output value is simply the collection of input messages
+   *
+   * @param sessionKeyFunction  function to calculate session window key
+   * @param <M>  type of input {@link Message}
+   * @param <WK>  type of the session window key
+   * @return  the {@link Window} function for the session
+   */
+  public static <M extends Message, WK> Window<M, WK, Collection<M>, WindowOutput<WK, Collection<M>>> intoSessions(Function<M, WK> sessionKeyFunction) {
+    return new SessionWindow<>(sessionKeyFunction, (m, c) -> { c.add(m); return c; });
+  }
+
+  /**
+   * Static API method to create a {@link SessionWindow} in which the output value is a collection of {@code SI} from the input messages
+   *
+   * @param sessionKeyFunction  function to calculate session window key
+   * @param sessionInfoExtractor  function to retrieve session info of type {@code SI} from the input message of type {@code M}
+   * @param <M>  type of the input {@link Message}
+   * @param <WK>  type of the session window key
+   * @param <SI>  type of the session information retrieved from each input message of type {@code M}
+   * @return  the {@link Window} function for the session
+   */
+  public static <M extends Message, WK, SI> Window<M, WK, Collection<SI>, WindowOutput<WK, Collection<SI>>> intoSessions(Function<M, WK> sessionKeyFunction,
+      Function<M, SI> sessionInfoExtractor) {
+    return new SessionWindow<>(sessionKeyFunction,
+        (m, c) -> { c.add(sessionInfoExtractor.apply(m)); return c; } );
+  }
+
+  /**
+   * Static API method to create a {@link SessionWindow} as a counter of input messages
+   *
+   * @param sessionKeyFunction  function to calculate session window key
+   * @param <M>  type of the input {@link Message}
+   * @param <WK>  type of the session window key
+   * @return  the {@link Window} function for the session
+   */
+  public static <M extends Message, WK> Window<M, WK, Integer, WindowOutput<WK, Integer>> intoSessionCounter(Function<M, WK> sessionKeyFunction) {
+    return new SessionWindow<>(sessionKeyFunction, (m, c) -> c + 1);
+  }
+
+}

http://git-wip-us.apache.org/repos/asf/samza/blob/fbdd76da/samza-operator/src/main/java/org/apache/samza/operators/api/data/Data.java
----------------------------------------------------------------------
diff --git a/samza-operator/src/main/java/org/apache/samza/operators/api/data/Data.java b/samza-operator/src/main/java/org/apache/samza/operators/api/data/Data.java
new file mode 100644
index 0000000..69a3bee
--- /dev/null
+++ b/samza-operator/src/main/java/org/apache/samza/operators/api/data/Data.java
@@ -0,0 +1,57 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you 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.
+ */
+
+package org.apache.samza.operators.api.data;
+
+import java.util.List;
+import java.util.Map;
+
+
+/**
+ * A generic data interface that allows to implement data access / deserialization w/ {@link Schema}
+ */
+public interface Data {
+
+  Schema schema();
+
+  Object value();
+
+  int intValue();
+
+  long longValue();
+
+  float floatValue();
+
+  double doubleValue();
+
+  boolean booleanValue();
+
+  String strValue();
+
+  byte[] bytesValue();
+
+  List<Object> arrayValue();
+
+  Map<Object, Object> mapValue();
+
+  Data getElement(int index);
+
+  Data getFieldData(String fldName);
+
+}

http://git-wip-us.apache.org/repos/asf/samza/blob/fbdd76da/samza-operator/src/main/java/org/apache/samza/operators/api/data/IncomingSystemMessage.java
----------------------------------------------------------------------
diff --git a/samza-operator/src/main/java/org/apache/samza/operators/api/data/IncomingSystemMessage.java b/samza-operator/src/main/java/org/apache/samza/operators/api/data/IncomingSystemMessage.java
new file mode 100644
index 0000000..ba74618
--- /dev/null
+++ b/samza-operator/src/main/java/org/apache/samza/operators/api/data/IncomingSystemMessage.java
@@ -0,0 +1,76 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you 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.
+ */
+package org.apache.samza.operators.api.data;
+
+import org.apache.samza.system.IncomingMessageEnvelope;
+import org.apache.samza.system.SystemStreamPartition;
+
+
+/**
+ * This class implements a {@link Message} that encapsulates an {@link IncomingMessageEnvelope} from the system
+ *
+ */
+public class IncomingSystemMessage implements Message<Object, Object>, InputSystemMessage<Offset> {
+  /**
+   * Incoming message envelope
+   */
+  private final IncomingMessageEnvelope imsg;
+
+  /**
+   * The receive time of this incoming message
+   */
+  private final long recvTimeNano;
+
+  /**
+   * Ctor to create a {@code IncomingSystemMessage} from {@link IncomingMessageEnvelope}
+   *
+   * @param imsg The incoming system message
+   */
+  public IncomingSystemMessage(IncomingMessageEnvelope imsg) {
+    this.imsg = imsg;
+    this.recvTimeNano = System.nanoTime();
+  }
+
+  @Override
+  public Object getMessage() {
+    return this.imsg.getMessage();
+  }
+
+  @Override
+  public Object getKey() {
+    return this.imsg.getKey();
+  }
+
+  @Override
+  public long getTimestamp() {
+    return this.recvTimeNano;
+  }
+
+  @Override
+  public Offset getOffset() {
+    // TODO: need to add offset factory to generate different types of offset. This is just a placeholder,
+    // assuming incoming message carries long value as offset (i.e. Kafka case)
+    return new LongOffset(this.imsg.getOffset());
+  }
+
+  @Override
+  public SystemStreamPartition getSystemStreamPartition() {
+    return imsg.getSystemStreamPartition();
+  }
+}

http://git-wip-us.apache.org/repos/asf/samza/blob/fbdd76da/samza-operator/src/main/java/org/apache/samza/operators/api/data/InputSystemMessage.java
----------------------------------------------------------------------
diff --git a/samza-operator/src/main/java/org/apache/samza/operators/api/data/InputSystemMessage.java b/samza-operator/src/main/java/org/apache/samza/operators/api/data/InputSystemMessage.java
new file mode 100644
index 0000000..c786025
--- /dev/null
+++ b/samza-operator/src/main/java/org/apache/samza/operators/api/data/InputSystemMessage.java
@@ -0,0 +1,43 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you 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.
+ */
+package org.apache.samza.operators.api.data;
+
+import org.apache.samza.system.SystemStreamPartition;
+
+
+/**
+ * This interface defines additional methods a message from an system input should implement, including the methods to
+ * get {@link SystemStreamPartition} and the {@link Offset} of the input system message.
+ */
+public interface InputSystemMessage<O extends Offset> {
+
+  /**
+   * Get the input message's {@link SystemStreamPartition}
+   *
+   * @return  the {@link SystemStreamPartition} this message is coming from
+   */
+  SystemStreamPartition getSystemStreamPartition();
+
+  /**
+   * Get the offset of the message in the input stream. This should be used to uniquely identify a message in an input stream.
+   *
+   * @return The offset of the message in the input stream.
+   */
+  O getOffset();
+}

http://git-wip-us.apache.org/repos/asf/samza/blob/fbdd76da/samza-operator/src/main/java/org/apache/samza/operators/api/data/LongOffset.java
----------------------------------------------------------------------
diff --git a/samza-operator/src/main/java/org/apache/samza/operators/api/data/LongOffset.java b/samza-operator/src/main/java/org/apache/samza/operators/api/data/LongOffset.java
new file mode 100644
index 0000000..f059b33
--- /dev/null
+++ b/samza-operator/src/main/java/org/apache/samza/operators/api/data/LongOffset.java
@@ -0,0 +1,75 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you 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.
+ */
+
+package org.apache.samza.operators.api.data;
+
+/**
+ * An implementation of {@link org.apache.samza.operators.api.data.Offset}, w/ {@code long} value as the offset
+ */
+public class LongOffset implements Offset {
+
+  /**
+   * The offset value in {@code long}
+   */
+  private final Long offset;
+
+  private LongOffset(long offset) {
+    this.offset = offset;
+  }
+
+  public LongOffset(String offset) {
+    this.offset = Long.valueOf(offset);
+  }
+
+  @Override
+  public int compareTo(Offset o) {
+    if (!(o instanceof LongOffset)) {
+      throw new IllegalArgumentException("Not comparable offset classes. LongOffset vs " + o.getClass().getName());
+    }
+    LongOffset other = (LongOffset) o;
+    return this.offset.compareTo(other.offset);
+  }
+
+  @Override
+  public boolean equals(Object other) {
+    if (!(other instanceof LongOffset)) {
+      return false;
+    }
+    LongOffset o = (LongOffset) other;
+    return this.offset.equals(o.offset);
+  }
+
+  /**
+   * Helper method to get the minimum offset
+   *
+   * @return The minimum offset
+   */
+  public static LongOffset getMinOffset() {
+    return new LongOffset(Long.MIN_VALUE);
+  }
+
+  /**
+   * Helper method to get the maximum offset
+   *
+   * @return The maximum offset
+   */
+  public static LongOffset getMaxOffset() {
+    return new LongOffset(Long.MAX_VALUE);
+  }
+}

http://git-wip-us.apache.org/repos/asf/samza/blob/fbdd76da/samza-operator/src/main/java/org/apache/samza/operators/api/data/Message.java
----------------------------------------------------------------------
diff --git a/samza-operator/src/main/java/org/apache/samza/operators/api/data/Message.java b/samza-operator/src/main/java/org/apache/samza/operators/api/data/Message.java
new file mode 100644
index 0000000..9b53b45
--- /dev/null
+++ b/samza-operator/src/main/java/org/apache/samza/operators/api/data/Message.java
@@ -0,0 +1,58 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you 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.
+ */
+
+package org.apache.samza.operators.api.data;
+
+/**
+ * This class defines the generic interface of {@link Message}, which is a entry in the input/output stream.
+ *
+ * <p>The {@link Message} models the basic operatible unit in streaming SQL processes in Samza.
+ *
+ */
+public interface Message<K, M> {
+
+  /**
+   * Access method to get the corresponding message body in {@link Message}
+   *
+   * @return Message object in this {@link Message}
+   */
+  M getMessage();
+
+  /**
+   * Method to indicate whether this {@link Message} indicates deletion of a message w/ the message key
+   *
+   * @return A boolean value indicates whether the current message is a delete or insert message
+   */
+  default boolean isDelete() { return false; };
+
+  /**
+   * Access method to the key of the message
+   *
+   * @return The key of the message
+   */
+  K getKey();
+
+  /**
+   * Get the message creation timestamp of the message.
+   *
+   * @return The message's timestamp in nano seconds.
+   */
+  long getTimestamp();
+
+}

http://git-wip-us.apache.org/repos/asf/samza/blob/fbdd76da/samza-operator/src/main/java/org/apache/samza/operators/api/data/Offset.java
----------------------------------------------------------------------
diff --git a/samza-operator/src/main/java/org/apache/samza/operators/api/data/Offset.java b/samza-operator/src/main/java/org/apache/samza/operators/api/data/Offset.java
new file mode 100644
index 0000000..0fac2c0
--- /dev/null
+++ b/samza-operator/src/main/java/org/apache/samza/operators/api/data/Offset.java
@@ -0,0 +1,27 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you 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.
+ */
+
+package org.apache.samza.operators.api.data;
+
+/**
+ * A generic interface extending {@link java.lang.Comparable} to be used as {@code Offset} in a stream
+ */
+public interface Offset extends Comparable<Offset> {
+
+}

http://git-wip-us.apache.org/repos/asf/samza/blob/fbdd76da/samza-operator/src/main/java/org/apache/samza/operators/api/data/Schema.java
----------------------------------------------------------------------
diff --git a/samza-operator/src/main/java/org/apache/samza/operators/api/data/Schema.java b/samza-operator/src/main/java/org/apache/samza/operators/api/data/Schema.java
new file mode 100644
index 0000000..dc3f8f4
--- /dev/null
+++ b/samza-operator/src/main/java/org/apache/samza/operators/api/data/Schema.java
@@ -0,0 +1,58 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you 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.
+ */
+
+package org.apache.samza.operators.api.data;
+
+import java.util.Map;
+
+
+/**
+ * This defines an interface for generic schema access methods
+ */
+public interface Schema {
+
+  enum Type {
+    INTEGER,
+    LONG,
+    FLOAT,
+    DOUBLE,
+    BOOLEAN,
+    STRING,
+    BYTES,
+    STRUCT,
+    ARRAY,
+    MAP
+  };
+
+  Type getType();
+
+  Schema getElementType();
+
+  Schema getValueType();
+
+  Map<String, Schema> getFields();
+
+  Schema getFieldType(String fldName);
+
+  Data read(Object object);
+
+  Data transform(Data inputData);
+
+  boolean equals(Schema other);
+}

http://git-wip-us.apache.org/repos/asf/samza/blob/fbdd76da/samza-operator/src/main/java/org/apache/samza/operators/api/internal/Operators.java
----------------------------------------------------------------------
diff --git a/samza-operator/src/main/java/org/apache/samza/operators/api/internal/Operators.java b/samza-operator/src/main/java/org/apache/samza/operators/api/internal/Operators.java
new file mode 100644
index 0000000..f220285
--- /dev/null
+++ b/samza-operator/src/main/java/org/apache/samza/operators/api/internal/Operators.java
@@ -0,0 +1,468 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you 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.
+ */
+
+package org.apache.samza.operators.api.internal;
+
+import org.apache.samza.operators.api.MessageStream;
+import org.apache.samza.operators.api.WindowState;
+import org.apache.samza.operators.api.data.Message;
+import org.apache.samza.storage.kv.Entry;
+import org.apache.samza.task.MessageCollector;
+import org.apache.samza.task.TaskCoordinator;
+
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.UUID;
+import java.util.function.BiFunction;
+import java.util.function.Function;
+
+
+/**
+ * This class defines all basic stream operator classes used by internal implementation only. All classes defined in
+ * this file are immutable.
+ *
+ * NOTE: Programmers should not use the operators defined in this class directly. All {@link Operator} objects
+ * should be initiated via {@link MessageStream} API methods
+ */
+public class Operators {
+  /**
+   * Private constructor to prevent instantiation of the {@link Operators} class
+   */
+  private Operators() {}
+
+  private static String getOperatorId() {
+    // TODO: need to change the IDs to be a consistent, durable IDs that can be recovered across container and job restarts
+    return UUID.randomUUID().toString();
+  }
+
+  /**
+   * Private interface for stream operator functions. The interface class defines the output of the stream operator function.
+   *
+   */
+  private interface Operator<OM extends Message> {
+    MessageStream<OM> getOutputStream();
+  }
+
+  /**
+   * Linear stream operator function that takes 1 input {@link Message} and output a collection of output {@link Message}s.
+   *
+   * @param <M>  the type of input {@link Message}
+   * @param <OM>  the type of output {@link Message}
+   */
+  public static class StreamOperator<M extends Message, OM extends Message> implements Operator<OM> {
+    /**
+     * The output {@link MessageStream}
+     */
+    private final MessageStream<OM> outputStream;
+
+    /**
+     * The transformation function
+     */
+    private final Function<M, Collection<OM>> txfmFunction;
+
+    /**
+     * Constructor of {@link StreamOperator}. Make it private s.t. it can only be created within {@link Operators}.
+     *
+     * @param transformFn  the transformation function to be applied that transforms 1 input {@link Message} into a collection
+     *                     of output {@link Message}s
+     */
+    private StreamOperator(Function<M, Collection<OM>> transformFn) {
+      this(transformFn, new MessageStream<>());
+    }
+
+    /**
+     * Constructor of {@link StreamOperator} which allows the user to define the output {@link MessageStream}
+     *
+     * @param transformFn  the transformation function
+     * @param outputStream  the output {@link MessageStream}
+     */
+    private StreamOperator(Function<M, Collection<OM>> transformFn, MessageStream<OM> outputStream) {
+      this.outputStream = outputStream;
+      this.txfmFunction = transformFn;
+    }
+
+    @Override
+    public MessageStream<OM> getOutputStream() {
+      return this.outputStream;
+    }
+
+    /**
+     * Method to get the transformation function.
+     *
+     * @return the {@code txfmFunction}
+     */
+    public Function<M, Collection<OM>> getFunction() {
+      return this.txfmFunction;
+    }
+
+  }
+
+  /**
+   * A sink operator function that allows customized code to send the output to external system. This is the terminal
+   * operator that does not have any output {@link MessageStream} that allows further processing in the same {@link org.apache.samza.task.StreamOperatorTask}
+   *
+   * @param <M>  the type of input {@link Message}
+   */
+  public static class SinkOperator<M extends Message> implements Operator {
+
+    /**
+     * The user-defined sink function
+     */
+    private final MessageStream.VoidFunction3<M, MessageCollector, TaskCoordinator> sink;
+
+    /**
+     * Default constructor for {@link SinkOperator}. Make it private s.t. it can only be created within {@link Operators}.
+     *
+     * @param sink  the user-defined sink function
+     */
+    private SinkOperator(MessageStream.VoidFunction3<M, MessageCollector, TaskCoordinator> sink) {
+      this.sink = sink;
+    }
+
+    @Override
+    public MessageStream getOutputStream() {
+      return null;
+    }
+
+    /**
+     * Method to get the user-defined function implements the {@link SinkOperator}
+     *
+     * @return a {@link MessageStream.VoidFunction3} function that allows the caller to pass in an input message, {@link MessageCollector}
+     *         and {@link TaskCoordinator} to the sink function
+     */
+    public MessageStream.VoidFunction3<M, MessageCollector, TaskCoordinator> getFunction() {
+      return this.sink;
+    }
+  }
+
+  /**
+   * The store functions that are used by {@link WindowOperator} and {@link PartialJoinOperator} to store and retrieve
+   * buffered messages and partial aggregation results
+   *
+   * @param <SK>  the type of key used to store the operator states
+   * @param <SS>  the type of operator state. e.g. could be the partial aggregation result for a window, or a buffered
+   *             input message from the join stream for a join
+   */
+  public static class StoreFunctions<M extends Message, SK, SS> {
+    /**
+     * Function to define the key to query in the operator state store, according to the incoming {@link Message}
+     * This method only supports finding the unique key for the incoming message, which supports use case of non-overlapping
+     * windows and unique-key-based join.
+     *
+     * TODO: for windows that overlaps (i.e. sliding windows and hopping windows) and non-unique-key-based join, the query
+     * to the state store is usually a range scan. We need to add a rangeKeyFinder function to map from a single input
+     * message to a range of keys in the store.
+     */
+    private final Function<M, SK> storeKeyFinder;
+
+    /**
+     * Function to update the store entry based on the current state and the incoming {@link Message}
+     *
+     * TODO: this is assuming a 1:1 mapping from the input message to the store entry. When implementing sliding/hopping
+     * windows and non-unique-key-based join, we may need to include the corresponding state key, in addition to the
+     * state value.
+     */
+    private final BiFunction<M, SS, SS> stateUpdater;
+
+    /**
+     * Constructor of state store functions.
+     *
+     */
+    private StoreFunctions(Function<M, SK> keyFinder,
+        BiFunction<M, SS, SS> stateUpdater) {
+      this.storeKeyFinder = keyFinder;
+      this.stateUpdater = stateUpdater;
+    }
+
+    /**
+     * Method to get the {@code storeKeyFinder} function
+     *
+     * @return  the function to calculate the key from an input {@link Message}
+     */
+    public Function<M, SK> getStoreKeyFinder() {
+      return this.storeKeyFinder;
+    }
+
+    /**
+     * Method to get the {@code stateUpdater} function
+     *
+     * @return  the function to update the corresponding state according to an input {@link Message}
+     */
+    public BiFunction<M, SS, SS> getStateUpdater() {
+      return this.stateUpdater;
+    }
+  }
+
+  /**
+   * Defines a window operator function that takes one {@link MessageStream} as an input, accumulate the window state, and generate
+   * an output {@link MessageStream} w/ output type {@code WM} which extends {@link WindowOutput}
+   *
+   * @param <M>  the type of input {@link Message}
+   * @param <WK>  the type of key in the output {@link Message} from the {@link WindowOperator} function
+   * @param <WS>  the type of window state in the {@link WindowOperator} function
+   * @param <WM>  the type of window output {@link Message}
+   */
+  public static class WindowOperator<M extends Message, WK, WS extends WindowState, WM extends WindowOutput<WK, ?>> implements Operator<WM> {
+    /**
+     * The output {@link MessageStream}
+     */
+    private final MessageStream<WM> outputStream;
+
+    /**
+     * The main window transformation function that takes {@link Message}s from one input stream, aggregates w/ the window
+     * state(s) from the window state store, and generate output {@link Message}s to the output stream.
+     */
+    private final BiFunction<M, Entry<WK, WS>, WM> txfmFunction;
+
+    /**
+     * The state store functions for the {@link WindowOperator}
+     */
+    private final StoreFunctions<M, WK, WS> storeFunctions;
+
+    /**
+     * The window trigger function
+     */
+    private final Trigger<M, WS> trigger;
+
+    /**
+     * The unique ID of stateful operators
+     */
+    private final String opId;
+
+    /**
+     * Constructor for {@link WindowOperator}. Make it private s.t. it can only be created within {@link Operators}.
+     *
+     * @param windowFn  description of the window function
+     * @param operatorId  auto-generated unique ID of the operator
+     */
+    private WindowOperator(WindowFn<M, WK, WS, WM> windowFn, String operatorId) {
+      this.outputStream = new MessageStream<>();
+      this.txfmFunction = windowFn.getTransformFunc();
+      this.storeFunctions = windowFn.getStoreFuncs();
+      this.trigger = windowFn.getTrigger();
+      this.opId = operatorId;
+    }
+
+    @Override
+    public String toString() {
+      return this.opId;
+    }
+
+    @Override
+    public MessageStream<WM> getOutputStream() {
+      return this.outputStream;
+    }
+
+    /**
+     * Method to get the window's {@link StoreFunctions}.
+     *
+     * @return  the window operator's {@code storeFunctions}
+     */
+    public StoreFunctions<M, WK, WS> getStoreFunctions() {
+      return this.storeFunctions;
+    }
+
+    /**
+     * Method to get the window operator's main function
+     *
+     * @return   the window operator's {@code txfmFunction}
+     */
+    public BiFunction<M, Entry<WK, WS>, WM> getFunction() {
+      return this.txfmFunction;
+    }
+
+    /**
+     * Method to get the trigger functions
+     *
+     * @return  the {@link Trigger} for this {@link WindowOperator}
+     */
+    public Trigger<M, WS> getTrigger() {
+      return this.trigger;
+    }
+
+    /**
+     * Method to generate the window operator's state store name
+     *
+     * @param inputStream the input {@link MessageStream} to this state store
+     * @return   the persistent store name of the window operator
+     */
+    public String getStoreName(MessageStream<M> inputStream) {
+      //TODO: need to get the persistent name of ds and the operator in a serialized form
+      return String.format("input-%s-wndop-%s", inputStream.toString(), this.toString());
+    }
+  }
+
+  /**
+   * The partial join operator that takes {@link Message}s from one input stream and join w/ buffered {@link Message}s from
+   * another stream and generate join output to {@code output}
+   *
+   * @param <M>  the type of input {@link Message}
+   * @param <K>  the type of join key
+   * @param <JM>  the type of message of {@link Message} in the other join stream
+   * @param <RM>  the type of message of {@link Message} in the join output stream
+   */
+  public static class PartialJoinOperator<M extends Message<K, ?>, K, JM extends Message<K, ?>, RM extends Message> implements Operator<RM> {
+
+    private final MessageStream<RM> joinOutput;
+
+    /**
+     * The main transformation function of {@link PartialJoinOperator} that takes a type {@code M} input message,
+     * join w/ a stream of buffered {@link Message}s from another stream w/ type {@code JM}, and generate joined type {@code RM}.
+     */
+    private final BiFunction<M, JM, RM> txfmFunction;
+
+    /**
+     * The message store functions that read the buffered messages from the other stream in the join
+     */
+    private final StoreFunctions<JM, K, JM> joinStoreFunctions;
+
+    /**
+     * The message store functions that save the buffered messages of this {@link MessageStream} in the join
+     */
+    private final StoreFunctions<M, K, M> selfStoreFunctions;
+
+    /**
+     * The unique ID for the stateful operator
+     */
+    private final String opId;
+
+    /**
+     * Default constructor to create a {@link PartialJoinOperator} object
+     *
+     * @param partialJoin  partial join function that take type {@code M} of input {@link Message} and join w/ type
+     *                     {@code JM} of buffered {@link Message} from another stream
+     * @param joinOutput  the output {@link MessageStream} of the join results
+     */
+    private PartialJoinOperator(BiFunction<M, JM, RM> partialJoin, MessageStream<RM> joinOutput, String opId) {
+      this.joinOutput = joinOutput;
+      this.txfmFunction = partialJoin;
+      // Read-only join store, no creator/updater functions specified
+      this.joinStoreFunctions = new StoreFunctions<>(m -> m.getKey(), null);
+      // Buffered message store for this input stream
+      this.selfStoreFunctions = new StoreFunctions<>(m -> m.getKey(), (m, s1) -> m);
+      this.opId = opId;
+    }
+
+    @Override
+    public String toString() {
+      return this.opId;
+    }
+
+    @Override
+    public MessageStream<RM> getOutputStream() {
+      return this.joinOutput;
+    }
+
+    /**
+     * Method to get {@code joinStoreFunctions}
+     *
+     * @return  {@code joinStoreFunctions}
+     */
+    public StoreFunctions<JM, K, JM> getJoinStoreFunctions() {
+      return this.joinStoreFunctions;
+    }
+
+    /**
+     * Method to get {@code selfStoreFunctions}
+     *
+     * @return  {@code selfStoreFunctions}
+     */
+    public StoreFunctions<M, K, M> getSelfStoreFunctions() {
+      return this.selfStoreFunctions;
+    }
+
+    /**
+     * Method to get {@code txfmFunction}
+     *
+     * @return  {@code txfmFunction}
+     */
+    public BiFunction<M, JM, RM> getFunction() {
+      return this.txfmFunction;
+    }
+  }
+
+  /**
+   * The method only to be used internally in {@link MessageStream} to create {@link StreamOperator}
+   *
+   * @param transformFn  the corresponding transformation function
+   * @param <M>  type of input {@link Message}
+   * @param <OM>  type of output {@link Message}
+   * @return  the {@link StreamOperator}
+   */
+  public static <M extends Message, OM extends Message> StreamOperator<M, OM> getStreamOperator(Function<M, Collection<OM>> transformFn) {
+    return new StreamOperator<>(transformFn);
+  }
+
+  /**
+   * The method only to be used internally in {@link MessageStream} to create {@link SinkOperator}
+   *
+   * @param sinkFn  the sink function
+   * @param <M>  type of input {@link Message}
+   * @return   the {@link SinkOperator}
+   */
+  public static <M extends Message> SinkOperator<M> getSinkOperator(MessageStream.VoidFunction3<M, MessageCollector, TaskCoordinator> sinkFn) {
+    return new SinkOperator<>(sinkFn);
+  }
+
+  /**
+   * The method only to be used internally in {@link MessageStream} to create {@link WindowOperator}
+   *
+   * @param windowFn  the {@link WindowFn} function
+   * @param <M>  type of input {@link Message}
+   * @param <WK>  type of window key
+   * @param <WS>  type of {@link WindowState}
+   * @param <WM>  type of output {@link WindowOutput}
+   * @return  the {@link WindowOperator}
+   */
+  public static <M extends Message, WK, WS extends WindowState, WM extends WindowOutput<WK, ?>> WindowOperator<M, WK, WS, WM> getWindowOperator(
+    WindowFn<M, WK, WS, WM> windowFn) {
+    return new WindowOperator<>(windowFn, Operators.getOperatorId());
+  }
+
+  /**
+   * The method only to be used internally in {@link MessageStream} to create {@link WindowOperator}
+   *
+   * @param joiner  the {@link WindowFn} function
+   * @param joinOutput  the output {@link MessageStream}
+   * @param <M>  type of input {@link Message}
+   * @param <K>  type of join key
+   * @param <JM>  the type of message in the {@link Message} from the other join stream
+   * @param <RM>  the type of message in the {@link Message} from the join function
+   * @return  the {@link PartialJoinOperator}
+   */
+  public static <M extends Message<K, ?>, K, JM extends Message<K, ?>, RM extends Message> PartialJoinOperator<M, K, JM, RM> getPartialJoinOperator(
+    BiFunction<M, JM, RM> joiner, MessageStream<RM> joinOutput) {
+    return new PartialJoinOperator<>(joiner, joinOutput, Operators.getOperatorId());
+  }
+
+  /**
+   * The method only to be used internally in {@link MessageStream} to create {@link StreamOperator} as a merger function
+   *
+   * @param mergeOutput  the common output {@link MessageStream} from the merger
+   * @param <M>  the type of input {@link Message}
+   * @return  the {@link StreamOperator} for merge
+   */
+  public static <M extends Message> StreamOperator<M, M> getMergeOperator(MessageStream<M> mergeOutput) {
+    return new StreamOperator<M, M>(t ->
+      new ArrayList<M>() {{
+        this.add(t);
+      }},
+      mergeOutput);
+  }
+}

http://git-wip-us.apache.org/repos/asf/samza/blob/fbdd76da/samza-operator/src/main/java/org/apache/samza/operators/api/internal/Trigger.java
----------------------------------------------------------------------
diff --git a/samza-operator/src/main/java/org/apache/samza/operators/api/internal/Trigger.java b/samza-operator/src/main/java/org/apache/samza/operators/api/internal/Trigger.java
new file mode 100644
index 0000000..33a0134
--- /dev/null
+++ b/samza-operator/src/main/java/org/apache/samza/operators/api/internal/Trigger.java
@@ -0,0 +1,95 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you 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.
+ */
+package org.apache.samza.operators.api.internal;
+
+import org.apache.samza.operators.api.WindowState;
+import org.apache.samza.operators.api.data.Message;
+
+import java.util.function.BiFunction;
+import java.util.function.Function;
+
+/**
+ * Defines the trigger functions for {@link Operators.WindowOperator}. This class is immutable.
+ *
+ * @param <M>  the type of message from the input stream
+ * @param <S>  the type of state variable in the window's state store
+ */
+public class Trigger<M extends Message, S extends WindowState> {
+
+  /**
+   * System timer based trigger condition. This is the only guarantee that the {@link Operators.WindowOperator} will proceed forward
+   */
+  private final Function<S, Boolean> timerTrigger;
+
+  /**
+   * early trigger condition that determines when to send the first output from the {@link Operators.WindowOperator}
+   */
+  private final BiFunction<M, S, Boolean> earlyTrigger;
+
+  /**
+   * late trigger condition that determines when to send the updated output after the first one from a {@link Operators.WindowOperator}
+   */
+  private final BiFunction<M, S, Boolean> lateTrigger;
+
+  /**
+   * the function to updated the window state when the first output is triggered
+   */
+  private final Function<S, S> earlyTriggerUpdater;
+
+  /**
+   * the function to updated the window state when the late output is triggered
+   */
+  private final Function<S, S> lateTriggerUpdater;
+
+  /**
+   * Private constructor to prevent instantiation
+   *
+   * @param timerTrigger  system timer trigger condition
+   * @param earlyTrigger  early trigger condition
+   * @param lateTrigger   late trigger condition
+   * @param earlyTriggerUpdater  early trigger state updater
+   * @param lateTriggerUpdater   late trigger state updater
+   */
+  private Trigger(Function<S, Boolean> timerTrigger, BiFunction<M, S, Boolean> earlyTrigger, BiFunction<M, S, Boolean> lateTrigger,
+      Function<S, S> earlyTriggerUpdater, Function<S, S> lateTriggerUpdater) {
+    this.timerTrigger = timerTrigger;
+    this.earlyTrigger = earlyTrigger;
+    this.lateTrigger = lateTrigger;
+    this.earlyTriggerUpdater = earlyTriggerUpdater;
+    this.lateTriggerUpdater = lateTriggerUpdater;
+  }
+
+  /**
+   * Static method to create a {@link Trigger} object
+   *
+   * @param timerTrigger  system timer trigger condition
+   * @param earlyTrigger  early trigger condition
+   * @param lateTrigger  late trigger condition
+   * @param earlyTriggerUpdater  early trigger state updater
+   * @param lateTriggerUpdater  late trigger state updater
+   * @param <M>  the type of input {@link Message}
+   * @param <S>  the type of window state extends {@link WindowState}
+   * @return  the {@link Trigger} function
+   */
+  public static <M extends Message, S extends WindowState> Trigger<M, S> createTrigger(Function<S, Boolean> timerTrigger,
+      BiFunction<M, S, Boolean> earlyTrigger, BiFunction<M, S, Boolean> lateTrigger, Function<S, S> earlyTriggerUpdater,
+      Function<S, S> lateTriggerUpdater) {
+    return new Trigger(timerTrigger, earlyTrigger, lateTrigger, earlyTriggerUpdater, lateTriggerUpdater);
+  }
+}

http://git-wip-us.apache.org/repos/asf/samza/blob/fbdd76da/samza-operator/src/main/java/org/apache/samza/operators/api/internal/WindowFn.java
----------------------------------------------------------------------
diff --git a/samza-operator/src/main/java/org/apache/samza/operators/api/internal/WindowFn.java b/samza-operator/src/main/java/org/apache/samza/operators/api/internal/WindowFn.java
new file mode 100644
index 0000000..1fd88e7
--- /dev/null
+++ b/samza-operator/src/main/java/org/apache/samza/operators/api/internal/WindowFn.java
@@ -0,0 +1,60 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you 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.
+ */
+package org.apache.samza.operators.api.internal;
+
+import org.apache.samza.operators.api.WindowState;
+import org.apache.samza.operators.api.data.Message;
+import org.apache.samza.storage.kv.Entry;
+
+import java.util.function.BiFunction;
+
+
+/**
+ * Defines an internal representation of a window function. This class SHOULD NOT be used by the programmer directly. It is used
+ * by the internal representation and implementation classes in operators.
+ *
+ * @param <M> type of input stream {@link Message} for window
+ * @param <WK>  type of window key in the output {@link Message}
+ * @param <WS>  type of {@link WindowState} variable in the state store
+ * @param <WM>  type of the message in the output stream
+ */
+public interface WindowFn<M extends Message, WK, WS extends WindowState, WM extends WindowOutput<WK, ?>> {
+
+  /**
+   * get the transformation function of the {@link WindowFn}
+   *
+   * @return  the transformation function takes type {@code M} message and the window state entry, then transform to an {@link WindowOutput}
+   */
+  BiFunction<M, Entry<WK, WS>, WM> getTransformFunc();
+
+  /**
+   * get the state store functions for this {@link WindowFn}
+   *
+   * @return  the collection of state store methods
+   */
+  Operators.StoreFunctions<M, WK, WS> getStoreFuncs();
+
+  /**
+   * get the trigger conditions for this {@link WindowFn}
+   *
+   * @return  the trigger condition for the {@link WindowFn} function
+   */
+  Trigger<M, WS> getTrigger();
+
+}