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diff --git a/api/src/main/java/io/opencensus/tags/TagContext.java b/api/src/main/java/io/opencensus/tags/TagContext.java
new file mode 100644
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+++ b/api/src/main/java/io/opencensus/tags/TagContext.java
@@ -0,0 +1,109 @@
+/*
+ * 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 java.util.HashMap;
+import java.util.Iterator;
+import javax.annotation.Nullable;
+import javax.annotation.concurrent.Immutable;
+
+/**
+ * A map from {@link TagKey} to {@link TagValue} that can be used to label anything that is
+ * associated with a specific operation.
+ *
+ * <p>For example, {@code TagContext}s can be used to label stats, log messages, or debugging
+ * information.
+ *
+ * @since 0.8
+ */
+@Immutable
+public abstract class TagContext {
+
+  /**
+   * Returns an iterator over the tags in this {@code TagContext}.
+   *
+   * @return an iterator over the tags in this {@code TagContext}.
+   * @since 0.8
+   */
+  // This method is protected to prevent client code from accessing the tags of any TagContext. We
+  // don't currently support efficient access to tags. However, every TagContext subclass needs to
+  // provide access to its tags to the stats and tagging implementations by implementing this
+  // method. If we decide to support access to tags in the future, we can add a public iterator()
+  // method and implement it for all subclasses by calling getIterator().
+  //
+  // The stats and tagging implementations can access any TagContext's tags through
+  // io.opencensus.tags.InternalUtils.getTags, which calls this method.
+  protected abstract Iterator<Tag> getIterator();
+
+  @Override
+  public String toString() {
+    return "TagContext";
+  }
+
+  /**
+   * Returns true iff the other object is an instance of {@code TagContext} and contains the same
+   * key-value pairs. Implementations are free to override this method to provide better
+   * performance.
+   */
+  @Override
+  public boolean equals(@Nullable Object other) {
+    if (!(other instanceof TagContext)) {
+      return false;
+    }
+    TagContext otherTags = (TagContext) other;
+    Iterator<Tag> iter1 = getIterator();
+    Iterator<Tag> iter2 = otherTags.getIterator();
+    HashMap<Tag, Integer> tags = new HashMap<Tag, Integer>();
+    while (iter1 != null && iter1.hasNext()) {
+      Tag tag = iter1.next();
+      if (tags.containsKey(tag)) {
+        tags.put(tag, tags.get(tag) + 1);
+      } else {
+        tags.put(tag, 1);
+      }
+    }
+    while (iter2 != null && iter2.hasNext()) {
+      Tag tag = iter2.next();
+      if (!tags.containsKey(tag)) {
+        return false;
+      }
+      int count = tags.get(tag);
+      if (count > 1) {
+        tags.put(tag, count - 1);
+      } else {
+        tags.remove(tag);
+      }
+    }
+    return tags.isEmpty();
+  }
+
+  @Override
+  public final int hashCode() {
+    int hashCode = 0;
+    Iterator<Tag> i = getIterator();
+    if (i == null) {
+      return hashCode;
+    }
+    while (i.hasNext()) {
+      Tag tag = i.next();
+      if (tag != null) {
+        hashCode += tag.hashCode();
+      }
+    }
+    return hashCode;
+  }
+}