Starting to experiment with flow tracking.
diff --git a/core/api/src/main/java/org/onlab/onos/net/intent/InstallableIntent.java b/core/api/src/main/java/org/onlab/onos/net/intent/InstallableIntent.java
index 66bc759..488695c 100644
--- a/core/api/src/main/java/org/onlab/onos/net/intent/InstallableIntent.java
+++ b/core/api/src/main/java/org/onlab/onos/net/intent/InstallableIntent.java
@@ -1,8 +1,22 @@
 package org.onlab.onos.net.intent;
 
+import org.onlab.onos.net.Link;
+
+import java.util.Collection;
+
 /**
  * Abstraction of an intent that can be installed into
  * the underlying system without additional compilation.
  */
 public interface InstallableIntent extends Intent {
+
+    /**
+     * Returns the collection of links that are required for this installable
+     * intent to exist.
+     *
+     * @return collection of links
+     */
+    // FIXME: replace this with 'NetworkResource'
+    Collection<Link> requiredLinks();
+
 }