Added application ID store; both trivial and distributed variants.
diff --git a/core/api/src/main/java/org/onlab/onos/core/ApplicationIdStore.java b/core/api/src/main/java/org/onlab/onos/core/ApplicationIdStore.java
new file mode 100644
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--- /dev/null
+++ b/core/api/src/main/java/org/onlab/onos/core/ApplicationIdStore.java
@@ -0,0 +1,52 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. The ASF licenses this file
+ * to you 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.onos.core;
+
+import java.util.Set;
+
+/**
+ * Manages application IDs.
+ */
+public interface ApplicationIdStore {
+
+ /**
+ * Returns the set of currently registered application identifiers.
+ *
+ * @return set of application ids
+ */
+ Set<ApplicationId> getAppIds();
+
+ /**
+ * Returns an existing application id from a given id.
+ * @param id the short value of the id
+ * @return an application id
+ */
+ ApplicationId getAppId(Short id);
+
+ /**
+ * Registers a new application by its name, which is expected
+ * to follow the reverse DNS convention, e.g.
+ * {@code org.flying.circus.app}
+ *
+ * @param identifier string identifier
+ * @return the application id
+ */
+ ApplicationId registerApplication(String identifier);
+
+}