Working on simple topology manager and provider
diff --git a/core/api/src/main/java/org/onlab/onos/event/EventAccumulator.java b/core/api/src/main/java/org/onlab/onos/event/EventAccumulator.java
new file mode 100644
index 0000000..e556afb
--- /dev/null
+++ b/core/api/src/main/java/org/onlab/onos/event/EventAccumulator.java
@@ -0,0 +1,26 @@
+package org.onlab.onos.event;
+
+import java.util.List;
+
+/**
+ * Abstraction of an accumulator capable of collecting events and at some
+ * point in time triggers processing of all previously accumulated events.
+ */
+public interface EventAccumulator {
+
+ /**
+ * Adds an event to the current batch. This operation may, or may not
+ * trigger processing of the current batch of events.
+ *
+ * @param event event to be added to the current batch
+ */
+ void add(Event event);
+
+ /**
+ * Processes the specified list of accumulated events.
+ *
+ * @param events list of accumulated events
+ */
+ void processEvents(List<Event> events);
+
+}