Introducing concept of a physical or logical region to facilitate
support of geographically distributed cluster and to lay ground
for multiple/filtered topology layouts.

Added implementation of manager and store; unit-tests included.

Change-Id: Ia01673a0b711b8785c0ea68768552c2f61d7ea6d
diff --git a/utils/misc/src/main/java/org/onlab/util/Identifier.java b/utils/misc/src/main/java/org/onlab/util/Identifier.java
new file mode 100644
index 0000000..7fcfcfe
--- /dev/null
+++ b/utils/misc/src/main/java/org/onlab/util/Identifier.java
@@ -0,0 +1,93 @@
+/*
+ * Copyright 2014-2016 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.onlab.util;
+
+import java.util.Objects;
+
+import static com.google.common.base.Preconditions.checkNotNull;
+
+/**
+ * Abstract identifier backed by another value, e.g. string, int.
+ */
+public class Identifier<T> {
+
+    protected final T identifier; // backing identifier value
+
+    /**
+     * Constructor for serialization.
+     */
+    protected Identifier() {
+        this.identifier = null;
+    }
+
+    /**
+     * Constructs an identifier backed by the specified value.
+     *
+     * @param value the backing value
+     */
+    protected Identifier(T value) {
+        this.identifier = checkNotNull(value, "Identifier cannot be null.");
+    }
+
+    /**
+     * Returns the backing identifier value.
+     *
+     * @return identifier
+     */
+    public T id() {
+        return identifier;
+    }
+
+    /**
+     * Returns the hashcode of the identifier.
+     *
+     * @return hashcode
+     */
+    @Override
+    public int hashCode() {
+        return identifier.hashCode();
+    }
+
+    /**
+     * Compares two device key identifiers for equality.
+     *
+     * @param obj to compare against
+     * @return true if the objects are equal, false otherwise.
+     */
+    @Override
+    public boolean equals(Object obj) {
+        if (this == obj) {
+            return true;
+        }
+        if (obj instanceof Identifier) {
+            Identifier that = (Identifier) obj;
+            return this.getClass() == that.getClass() &&
+                    Objects.equals(this.identifier, that.identifier);
+        }
+        return false;
+    }
+
+    /**
+     * Returns a string representation of a DeviceKeyId.
+     *
+     * @return string
+     */
+    public String toString() {
+        return identifier.toString();
+    }
+
+}
diff --git a/utils/misc/src/test/java/org/onlab/util/IdentifierTest.java b/utils/misc/src/test/java/org/onlab/util/IdentifierTest.java
new file mode 100644
index 0000000..dda556e
--- /dev/null
+++ b/utils/misc/src/test/java/org/onlab/util/IdentifierTest.java
@@ -0,0 +1,49 @@
+/*
+ * Copyright 2014-2016 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.onlab.util;
+
+import com.google.common.testing.EqualsTester;
+import org.junit.Test;
+
+import static org.junit.Assert.*;
+
+/**
+ * Test of the base identifier.
+ */
+public class IdentifierTest {
+
+    @Test
+    public void basics() {
+        FooId id = new FooId(123);
+        assertEquals("incorrect value", 123, (int) id.id());
+    }
+
+    @Test
+    public void equality() {
+        FooId a = new FooId(1);
+        FooId b = new FooId(1);
+        FooId c = new FooId(2);
+        new EqualsTester().addEqualityGroup(a, b).addEqualityGroup(c).testEquals();
+    }
+
+    static class FooId extends Identifier<Integer> {
+        FooId(int id) {
+            super(id);
+        }
+    }
+
+}
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