basic instructions implemented
diff --git a/core/api/src/main/java/org/onlab/onos/net/flow/TrafficSelector.java b/core/api/src/main/java/org/onlab/onos/net/flow/TrafficSelector.java
index 9678dc1..906e505 100644
--- a/core/api/src/main/java/org/onlab/onos/net/flow/TrafficSelector.java
+++ b/core/api/src/main/java/org/onlab/onos/net/flow/TrafficSelector.java
@@ -2,6 +2,8 @@
 
 import java.util.List;
 
+import org.onlab.onos.net.flow.criteria.Criterion;
+
 /**
  * Abstraction of a slice of network traffic.
  */