initial impl of criteria
diff --git a/core/api/src/main/java/org/onlab/onos/net/flow/criteria/Criterion.java b/core/api/src/main/java/org/onlab/onos/net/flow/criteria/Criterion.java
index d105f7c..567e100 100644
--- a/core/api/src/main/java/org/onlab/onos/net/flow/criteria/Criterion.java
+++ b/core/api/src/main/java/org/onlab/onos/net/flow/criteria/Criterion.java
@@ -1,5 +1,6 @@
 package org.onlab.onos.net.flow.criteria;
 
+
 /**
  * Representation of a single header field selection.
  */
@@ -92,6 +93,12 @@
         IPV6_EXTHDR
     }
 
+    /**
+     * Returns the type of criterion.
+     * @return type of criterion
+     */
+    public Type type();
+
     // TODO: Create factory class 'Criteria' that will have various factory
     // to create specific criterions.