Added DistributedPrimitive interface
Added AsyncDistributedSet that provides async set operations

Change-Id: I83494075a7973694ea6b7445ff4799b7a1a50641
diff --git a/core/api/src/main/java/org/onosproject/store/service/DistributedPrimitive.java b/core/api/src/main/java/org/onosproject/store/service/DistributedPrimitive.java
new file mode 100644
index 0000000..342a110
--- /dev/null
+++ b/core/api/src/main/java/org/onosproject/store/service/DistributedPrimitive.java
@@ -0,0 +1,78 @@
+/*
+ * Copyright 2015-2016 Open Networking Laboratory
+ *
+ * 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 org.onosproject.store.service;
+
+import org.onosproject.core.ApplicationId;
+
+/**
+ * Interface for all distributed primitives.
+ */
+public interface DistributedPrimitive {
+
+    /**
+     * Type of distributed primitive.
+     */
+    public enum Type {
+        /**
+         * Map with strong consistency semantics.
+         */
+        CONSISTENT_MAP,
+
+        /**
+         * Map with eventual consistency semantics.
+         */
+        EVENTUALLY_CONSISTENT_MAP,
+
+        /**
+         * distributed set.
+         */
+        SET,
+
+        /**
+         * atomic counter.
+         */
+        COUNTER,
+
+        /**
+         * Atomic value.
+         */
+        VALUE,
+
+        /**
+         * Distributed queue.
+         */
+        QUEUE
+    }
+
+    /**
+     * Returns the name of this primitive.
+     * @return name
+     */
+    String name();
+
+    /**
+     * Returns the type of primitive.
+     * @return primitive type
+     */
+    Type type();
+
+    /**
+     * Returns the application owning this primitive.
+     */
+    default ApplicationId applicationId() {
+        return null;
+    }
+}