Javadoc improvements
diff --git a/core/store/dist/src/main/java/org/onlab/onos/store/service/impl/DatabaseStateMachine.java b/core/store/dist/src/main/java/org/onlab/onos/store/service/impl/DatabaseStateMachine.java
index c974486..ad6773e 100644
--- a/core/store/dist/src/main/java/org/onlab/onos/store/service/impl/DatabaseStateMachine.java
+++ b/core/store/dist/src/main/java/org/onlab/onos/store/service/impl/DatabaseStateMachine.java
@@ -19,6 +19,13 @@
 
 import com.google.common.collect.Maps;
 
+/**
+ * StateMachine whose transitions are coordinated/replicated
+ * by Raft consensus.
+ * Each Raft cluster member has a instance of this state machine that is
+ * independently updated in lock step once there is consensus
+ * on the next transition.
+ */
 public class DatabaseStateMachine implements StateMachine {
 
     public static final KryoSerializer SERIALIZER = new KryoSerializer() {