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diff --git a/api/src/main/java/io/opencensus/tags/Tagger.java b/api/src/main/java/io/opencensus/tags/Tagger.java
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+++ b/api/src/main/java/io/opencensus/tags/Tagger.java
@@ -0,0 +1,86 @@
+/*
+ * Copyright 2017, OpenCensus 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.
+ */
+
+package io.opencensus.tags;
+
+import io.opencensus.common.Scope;
+
+/**
+ * Object for creating new {@link TagContext}s and {@code TagContext}s based on the current context.
+ *
+ * <p>This class returns {@link TagContextBuilder builders} that can be used to create the
+ * implementation-dependent {@link TagContext}s.
+ *
+ * <p>Implementations may have different constraints and are free to convert tag contexts to their
+ * own subtypes. This means callers cannot assume the {@link #getCurrentTagContext() current
+ * context} is the same instance as the one {@link #withTagContext(TagContext) placed into scope}.
+ *
+ * @since 0.8
+ */
+public abstract class Tagger {
+
+  /**
+   * Returns an empty {@code TagContext}.
+   *
+   * @return an empty {@code TagContext}.
+   * @since 0.8
+   */
+  public abstract TagContext empty();
+
+  /**
+   * Returns the current {@code TagContext}.
+   *
+   * @return the current {@code TagContext}.
+   * @since 0.8
+   */
+  public abstract TagContext getCurrentTagContext();
+
+  /**
+   * Returns a new empty {@code Builder}.
+   *
+   * @return a new empty {@code Builder}.
+   * @since 0.8
+   */
+  public abstract TagContextBuilder emptyBuilder();
+
+  /**
+   * Returns a builder based on this {@code TagContext}.
+   *
+   * @return a builder based on this {@code TagContext}.
+   * @since 0.8
+   */
+  public abstract TagContextBuilder toBuilder(TagContext tags);
+
+  /**
+   * Returns a new builder created from the current {@code TagContext}.
+   *
+   * @return a new builder created from the current {@code TagContext}.
+   * @since 0.8
+   */
+  public abstract TagContextBuilder currentBuilder();
+
+  /**
+   * Enters the scope of code where the given {@code TagContext} is in the current context
+   * (replacing the previous {@code TagContext}) and returns an object that represents that scope.
+   * The scope is exited when the returned object is closed.
+   *
+   * @param tags the {@code TagContext} to be set to the current context.
+   * @return an object that defines a scope where the given {@code TagContext} is set to the current
+   *     context.
+   * @since 0.8
+   */
+  public abstract Scope withTagContext(TagContext tags);
+}