Starting to experiment with flow tracking.
diff --git a/core/net/src/main/java/org/onlab/onos/net/intent/impl/FlowTrackerService.java b/core/net/src/main/java/org/onlab/onos/net/intent/impl/FlowTrackerService.java
new file mode 100644
index 0000000..b96de7c
--- /dev/null
+++ b/core/net/src/main/java/org/onlab/onos/net/intent/impl/FlowTrackerService.java
@@ -0,0 +1,44 @@
+package org.onlab.onos.net.intent.impl;
+
+import org.onlab.onos.net.Link;
+import org.onlab.onos.net.intent.IntentId;
+
+import java.util.Collection;
+
+/**
+ * Auxiliary service for tracking intent path flows and for notifying the
+ * intent service of environment changes via topology change delegate.
+ */
+public interface FlowTrackerService {
+
+ /**
+ * Sets a topology change delegate.
+ *
+ * @param delegate topology change delegate
+ */
+ void setDelegate(TopologyChangeDelegate delegate);
+
+ /**
+ * Unsets topology change delegate.
+ *
+ * @param delegate topology change delegate
+ */
+ void unsetDelegate(TopologyChangeDelegate delegate);
+
+ /**
+ * Adds a path flow to be tracked.
+ *
+ * @param intentId intent identity on whose behalf the path is being tracked
+ * @param resources resources to track
+ */
+ public void addTrackedResources(IntentId intentId, Collection<Link> resources);
+
+ /**
+ * Removes a path flow to be tracked.
+ *
+ * @param intentId intent identity on whose behalf the path is being tracked
+ * @param resources resources to stop tracking
+ */
+ public void removeTrackedResources(IntentId intentId, Collection<Link> resources);
+
+}