diff --git a/navalplanner-business/src/main/java/org/navalplanner/business/common/BaseEntity.java b/navalplanner-business/src/main/java/org/navalplanner/business/common/BaseEntity.java
index ddd0ee8ef..458f706cb 100644
--- a/navalplanner-business/src/main/java/org/navalplanner/business/common/BaseEntity.java
+++ b/navalplanner-business/src/main/java/org/navalplanner/business/common/BaseEntity.java
@@ -21,6 +21,12 @@
 
 package org.navalplanner.business.common;
 
+import java.util.Collection;
+import java.util.HashMap;
+import java.util.HashSet;
+import java.util.Map;
+import java.util.Set;
+
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
 import org.hibernate.validator.InvalidValue;
@@ -41,6 +47,24 @@ import org.navalplanner.business.util.deepcopy.Strategy;
  */
 public abstract class BaseEntity implements INewObject {
 
+    /**
+     * Groups the entities by id. Entities with null id are also included.
+     *
+     * @param entities
+     * @return entities grouped by id
+     */
+    public static <T extends BaseEntity> Map<Long, Set<T>> byId(
+            Collection<? extends T> entities) {
+        Map<Long, Set<T>> result = new HashMap<Long, Set<T>>();
+        for (T each : entities) {
+            if (!result.containsKey(each.getId())) {
+                result.put(each.getId(), new HashSet<T>());
+            }
+            result.get(each.getId()).add(each);
+        }
+        return result;
+    }
+
     private static final Log LOG = LogFactory.getLog(BaseEntity.class);
 
     @OnCopy(Strategy.IGNORE)
diff --git a/navalplanner-business/src/main/java/org/navalplanner/business/planner/entities/AssignedEffortDiscounting.java b/navalplanner-business/src/main/java/org/navalplanner/business/planner/entities/AssignedEffortDiscounting.java
index 89e11a7f1..5f072777b 100644
--- a/navalplanner-business/src/main/java/org/navalplanner/business/planner/entities/AssignedEffortDiscounting.java
+++ b/navalplanner-business/src/main/java/org/navalplanner/business/planner/entities/AssignedEffortDiscounting.java
@@ -20,21 +20,31 @@
  */
 package org.navalplanner.business.planner.entities;
 
+import java.util.Collection;
+import java.util.Collections;
+import java.util.Map;
+import java.util.Set;
+
 import org.joda.time.LocalDate;
+import org.navalplanner.business.common.BaseEntity;
 import org.navalplanner.business.resources.entities.Resource;
 import org.navalplanner.business.workingday.EffortDuration;
 
 public class AssignedEffortDiscounting implements
         IAssignedEffortForResource {
 
-    private final Object allocation;
+    private final Map<Long, Set<BaseEntity>> allocations;
 
-    AssignedEffortDiscounting(Object discountFrom) {
-        this.allocation = discountFrom;
+    public AssignedEffortDiscounting(BaseEntity allocationToDiscountFrom) {
+        this(Collections.singleton(allocationToDiscountFrom));
+    }
+
+    AssignedEffortDiscounting(Collection<? extends BaseEntity> discountFrom) {
+        this.allocations = BaseEntity.byId(discountFrom);
     }
 
     public EffortDuration getAssignedDurationAt(Resource resource, LocalDate day) {
-        return resource.getAssignedDurationDiscounting(allocation, day);
+        return resource.getAssignedDurationDiscounting(allocations, day);
     }
 
 }
\ No newline at end of file
diff --git a/navalplanner-business/src/main/java/org/navalplanner/business/planner/entities/DayAssignment.java b/navalplanner-business/src/main/java/org/navalplanner/business/planner/entities/DayAssignment.java
index 0e7a1801b..39b028b31 100644
--- a/navalplanner-business/src/main/java/org/navalplanner/business/planner/entities/DayAssignment.java
+++ b/navalplanner-business/src/main/java/org/navalplanner/business/planner/entities/DayAssignment.java
@@ -267,7 +267,26 @@ public abstract class DayAssignment extends BaseEntity {
 
     protected abstract void detachFromAllocation();
 
-    public abstract boolean belongsTo(Object allocation);
+    public final boolean belongsToSomeOf(Map<Long, Set<BaseEntity>> allocations) {
+        BaseEntity parent = getParent();
+        if (parent.getId() == null) {
+            Set<BaseEntity> entitiesWithNullId = allocations.get(null);
+            return entitiesWithNullId != null
+                    && entitiesWithNullId.contains(parent);
+        }
+        Set<BaseEntity> set = allocations.get(parent.getId());
+        return set != null;
+    }
+
+    protected abstract BaseEntity getParent();
+
+    public final boolean belongsTo(BaseEntity allocation) {
+        if (allocation == null) {
+            return false;
+        }
+        return belongsToSomeOf(BaseEntity.byId(Collections
+                .singleton(allocation)));
+    }
 
     /**
      * @return <code>null</code> if {@link DayAssignment this} day assignment
diff --git a/navalplanner-business/src/main/java/org/navalplanner/business/planner/entities/DerivedDayAssignment.java b/navalplanner-business/src/main/java/org/navalplanner/business/planner/entities/DerivedDayAssignment.java
index 4d17b1a53..b81a15a08 100644
--- a/navalplanner-business/src/main/java/org/navalplanner/business/planner/entities/DerivedDayAssignment.java
+++ b/navalplanner-business/src/main/java/org/navalplanner/business/planner/entities/DerivedDayAssignment.java
@@ -25,6 +25,7 @@ import static org.navalplanner.business.workingday.EffortDuration.hours;
 import org.apache.commons.lang.Validate;
 import org.hibernate.validator.NotNull;
 import org.joda.time.LocalDate;
+import org.navalplanner.business.common.BaseEntity;
 import org.navalplanner.business.resources.entities.Resource;
 import org.navalplanner.business.resources.entities.Worker;
 import org.navalplanner.business.scenarios.entities.Scenario;
@@ -165,9 +166,8 @@ public class DerivedDayAssignment extends DayAssignment {
     }
 
     @Override
-    public boolean belongsTo(Object allocation) {
-        return allocation != null
-                && parentState.getAllocation().equals(allocation);
+    protected BaseEntity getParent() {
+        return parentState.getAllocation();
     }
 
     @Override
diff --git a/navalplanner-business/src/main/java/org/navalplanner/business/planner/entities/GenericDayAssignment.java b/navalplanner-business/src/main/java/org/navalplanner/business/planner/entities/GenericDayAssignment.java
index e142d14de..44b34c439 100644
--- a/navalplanner-business/src/main/java/org/navalplanner/business/planner/entities/GenericDayAssignment.java
+++ b/navalplanner-business/src/main/java/org/navalplanner/business/planner/entities/GenericDayAssignment.java
@@ -30,6 +30,7 @@ import java.util.Set;
 import org.apache.commons.lang.Validate;
 import org.hibernate.validator.NotNull;
 import org.joda.time.LocalDate;
+import org.navalplanner.business.common.BaseEntity;
 import org.navalplanner.business.resources.entities.Resource;
 import org.navalplanner.business.scenarios.entities.Scenario;
 import org.navalplanner.business.util.deepcopy.OnCopy;
@@ -195,9 +196,8 @@ public class GenericDayAssignment extends DayAssignment {
     }
 
     @Override
-    public boolean belongsTo(Object allocation) {
-        return allocation != null
-                && getGenericResourceAllocation().equals(allocation);
+    protected BaseEntity getParent() {
+        return getGenericResourceAllocation();
     }
 
     @Override
diff --git a/navalplanner-business/src/main/java/org/navalplanner/business/planner/entities/SpecificDayAssignment.java b/navalplanner-business/src/main/java/org/navalplanner/business/planner/entities/SpecificDayAssignment.java
index 53b98556a..9660faefa 100644
--- a/navalplanner-business/src/main/java/org/navalplanner/business/planner/entities/SpecificDayAssignment.java
+++ b/navalplanner-business/src/main/java/org/navalplanner/business/planner/entities/SpecificDayAssignment.java
@@ -30,6 +30,7 @@ import java.util.Set;
 import org.apache.commons.lang.Validate;
 import org.hibernate.validator.NotNull;
 import org.joda.time.LocalDate;
+import org.navalplanner.business.common.BaseEntity;
 import org.navalplanner.business.resources.entities.Resource;
 import org.navalplanner.business.scenarios.entities.Scenario;
 import org.navalplanner.business.util.deepcopy.OnCopy;
@@ -186,9 +187,8 @@ public class SpecificDayAssignment extends DayAssignment {
     }
 
     @Override
-    public boolean belongsTo(Object resourceAllocation) {
-        return resourceAllocation != null
-                && getSpecificResourceAllocation().equals(resourceAllocation);
+    protected BaseEntity getParent() {
+        return getSpecificResourceAllocation();
     }
 
     @Override
diff --git a/navalplanner-business/src/main/java/org/navalplanner/business/resources/entities/Resource.java b/navalplanner-business/src/main/java/org/navalplanner/business/resources/entities/Resource.java
index 6a9cbe567..267a1b982 100644
--- a/navalplanner-business/src/main/java/org/navalplanner/business/resources/entities/Resource.java
+++ b/navalplanner-business/src/main/java/org/navalplanner/business/resources/entities/Resource.java
@@ -47,6 +47,7 @@ import org.navalplanner.business.calendars.entities.BaseCalendar;
 import org.navalplanner.business.calendars.entities.ICalendar;
 import org.navalplanner.business.calendars.entities.ResourceCalendar;
 import org.navalplanner.business.calendars.entities.SameWorkHoursEveryDay;
+import org.navalplanner.business.common.BaseEntity;
 import org.navalplanner.business.common.IntegrationEntity;
 import org.navalplanner.business.common.Registry;
 import org.navalplanner.business.common.exceptions.InstanceNotFoundException;
@@ -845,10 +846,13 @@ public abstract class Resource extends IntegrationEntity {
     }
 
     public EffortDuration getAssignedDurationDiscounting(
-            Object alloationFromWhichDiscountHours, LocalDate day) {
+            Map<Long, Set<BaseEntity>> allocationsFromWhichDiscountHours,
+            LocalDate day) {
         EffortDuration result = zero();
         for (DayAssignment dayAssignment : getAssignmentsForDay(day)) {
-            if (!dayAssignment.belongsTo(alloationFromWhichDiscountHours)) {
+
+            if (!dayAssignment
+                    .belongsToSomeOf(allocationsFromWhichDiscountHours)) {
                 result = result.plus(dayAssignment.getDuration());
             }
         }
diff --git a/navalplanner-business/src/test/java/org/navalplanner/business/test/planner/entities/DerivedAllocationGeneratorTest.java b/navalplanner-business/src/test/java/org/navalplanner/business/test/planner/entities/DerivedAllocationGeneratorTest.java
index a2ef5d64b..319fc896f 100644
--- a/navalplanner-business/src/test/java/org/navalplanner/business/test/planner/entities/DerivedAllocationGeneratorTest.java
+++ b/navalplanner-business/src/test/java/org/navalplanner/business/test/planner/entities/DerivedAllocationGeneratorTest.java
@@ -125,7 +125,7 @@ public class DerivedAllocationGeneratorTest {
     private Worker workerWithAlwaysAssignedHours(int assignedHours){
         Worker result = createNiceMock(Worker.class);
         expect(
-                result.getAssignedDurationDiscounting(isA(Object.class),
+                result.getAssignedDurationDiscounting(isA(Map.class),
                         isA(LocalDate.class))).andReturn(hours(assignedHours))
                 .anyTimes();
         replay(result);
diff --git a/navalplanner-business/src/test/java/org/navalplanner/business/test/planner/entities/GenericResourceAllocationTest.java b/navalplanner-business/src/test/java/org/navalplanner/business/test/planner/entities/GenericResourceAllocationTest.java
index 5169c0449..9299b2b43 100644
--- a/navalplanner-business/src/test/java/org/navalplanner/business/test/planner/entities/GenericResourceAllocationTest.java
+++ b/navalplanner-business/src/test/java/org/navalplanner/business/test/planner/entities/GenericResourceAllocationTest.java
@@ -169,7 +169,7 @@ public class GenericResourceAllocationTest {
     public static void mockZeroLoad(Resource... resources) {
         for (Resource each : resources) {
             expect(
-                    each.getAssignedDurationDiscounting(isA(Object.class),
+                    each.getAssignedDurationDiscounting(isA(Map.class),
                             isA(LocalDate.class))).andReturn(zero()).anyTimes();
         }
     }
@@ -223,7 +223,7 @@ public class GenericResourceAllocationTest {
         Worker result = createNiceMock(Worker.class);
         expect(result.getCalendar()).andReturn(resourceCalendar).anyTimes();
         expect(
-                result.getAssignedDurationDiscounting(isA(Object.class),
+                result.getAssignedDurationDiscounting(isA(Map.class),
                         isA(LocalDate.class))).andAnswer(
                 new IAnswer<EffortDuration>() {
 
@@ -807,7 +807,7 @@ public class GenericResourceAllocationTest {
             EffortDuration load) {
         VirtualWorker worker = createNiceMock(VirtualWorker.class);
         expect(
-                worker.getAssignedDurationDiscounting(isA(Object.class),
+                worker.getAssignedDurationDiscounting(isA(Map.class),
                         isA(LocalDate.class))).andReturn(load)
                 .anyTimes();
         expect(worker.getCalendar()).andReturn(