diff --git a/core/api/src/main/java/org/onlab/onos/net/resource/BandwidthResourceAllocation.java b/core/api/src/main/java/org/onlab/onos/net/resource/BandwidthResourceAllocation.java
index 77db287..86f8b4e 100644
--- a/core/api/src/main/java/org/onlab/onos/net/resource/BandwidthResourceAllocation.java
+++ b/core/api/src/main/java/org/onlab/onos/net/resource/BandwidthResourceAllocation.java
@@ -3,7 +3,8 @@
 /**
  * Representation of allocated bandwidth resource.
  */
-public class BandwidthResourceAllocation extends BandwidthResourceRequest {
+public class BandwidthResourceAllocation extends BandwidthResourceRequest
+        implements ResourceAllocation {
     /**
      * Creates a new {@link BandwidthResourceAllocation} with {@link Bandwidth}
      * object.
diff --git a/core/api/src/main/java/org/onlab/onos/net/resource/LambdaResourceAllocation.java b/core/api/src/main/java/org/onlab/onos/net/resource/LambdaResourceAllocation.java
index a8686ea..62ce1bd 100644
--- a/core/api/src/main/java/org/onlab/onos/net/resource/LambdaResourceAllocation.java
+++ b/core/api/src/main/java/org/onlab/onos/net/resource/LambdaResourceAllocation.java
@@ -3,7 +3,8 @@
 /**
  * Representation of allocated lambda resource.
  */
-public class LambdaResourceAllocation extends LambdaResourceRequest {
+public class LambdaResourceAllocation extends LambdaResourceRequest
+        implements ResourceAllocation {
     private final Lambda lambda;
 
     /**
diff --git a/core/api/src/main/java/org/onlab/onos/net/resource/LinkResourceAllocations.java b/core/api/src/main/java/org/onlab/onos/net/resource/LinkResourceAllocations.java
index a3d3e87..412cecd 100644
--- a/core/api/src/main/java/org/onlab/onos/net/resource/LinkResourceAllocations.java
+++ b/core/api/src/main/java/org/onlab/onos/net/resource/LinkResourceAllocations.java
@@ -1,5 +1,7 @@
 package org.onlab.onos.net.resource;
 
+import java.util.Set;
+
 import org.onlab.onos.net.Link;
 
 /**
@@ -12,5 +14,5 @@
      * @param link the target link
      * @return allocated resource for the link
      */
-    ResourceAllocation getResourceAllocation(Link link);
+    Set<ResourceAllocation> getResourceAllocation(Link link);
 }