Initial sketch of the virtual network constructs.

Change-Id: Ibcdafb9e56edb29fb37b80d7b0da321ad989c564
diff --git a/incubator/api/src/main/java/org/onosproject/incubator/net/virtual/TenantId.java b/incubator/api/src/main/java/org/onosproject/incubator/net/virtual/TenantId.java
new file mode 100644
index 0000000..a00f880
--- /dev/null
+++ b/incubator/api/src/main/java/org/onosproject/incubator/net/virtual/TenantId.java
@@ -0,0 +1,83 @@
+/*
+ * Copyright 2015 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.incubator.net.virtual;
+
+import com.google.common.annotations.Beta;
+
+import java.util.Objects;
+
+import static com.google.common.base.Preconditions.checkArgument;
+
+/**
+ * Representation of network tenant.
+ */
+@Beta
+public final class TenantId {
+
+    /**
+     * Represents no tenant, or an unspecified tenant.
+     */
+    public static final TenantId NONE = new TenantId();
+
+
+    private final String id;
+
+    // Public construction is prohibited
+    private TenantId(String id) {
+        checkArgument(id != null && id.length() > 0, "Tenant ID cannot be null or empty");
+        this.id = id;
+    }
+
+
+    // Default constructor for serialization
+    protected TenantId() {
+        this.id = "";
+    }
+
+    /**
+     * Creates a tenant id using the supplied backing id.
+     *
+     * @param id network id
+     * @return network identifier
+     */
+    public static TenantId tenantId(String id) {
+        return new TenantId(id);
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hash(id);
+    }
+
+    @Override
+    public boolean equals(Object obj) {
+        if (this == obj) {
+            return true;
+        }
+        if (obj instanceof TenantId) {
+            final TenantId that = (TenantId) obj;
+            return this.getClass() == that.getClass() &&
+                    Objects.equals(this.id, that.id);
+        }
+        return false;
+    }
+
+    @Override
+    public String toString() {
+        return id;
+    }
+
+}