diff --git a/navalplanner-business/src/main/java/org/navalplanner/business/orders/entities/OrderElement.java b/navalplanner-business/src/main/java/org/navalplanner/business/orders/entities/OrderElement.java
index 8d68b970d..3607f775d 100644
--- a/navalplanner-business/src/main/java/org/navalplanner/business/orders/entities/OrderElement.java
+++ b/navalplanner-business/src/main/java/org/navalplanner/business/orders/entities/OrderElement.java
@@ -803,7 +803,7 @@ public abstract class OrderElement extends BaseEntity implements
 
     private boolean checkAncestorsNoOtherLabelRepeated(Label newLabel) {
         for (Label label : labels) {
-            if (label.equals(newLabel)) {
+            if (label.isEqualTo(newLabel)) {
                 return false;
             }
         }
@@ -877,10 +877,9 @@ public abstract class OrderElement extends BaseEntity implements
         return null;
     }
 
-    public boolean containsLabel(String name, String type) {
+    public boolean containsLabel(String code) {
         for (Label label : getLabels()) {
-            if (label.getName().equals(name)
-                    && label.getType().getName().equals(type)) {
+            if (label.getCode().equals(code)) {
                 return true;
             }
         }
diff --git a/navalplanner-webapp/src/main/java/org/navalplanner/ws/common/api/LabelDTO.java b/navalplanner-webapp/src/main/java/org/navalplanner/ws/common/api/LabelReferenceDTO.java
similarity index 82%
rename from navalplanner-webapp/src/main/java/org/navalplanner/ws/common/api/LabelDTO.java
rename to navalplanner-webapp/src/main/java/org/navalplanner/ws/common/api/LabelReferenceDTO.java
index ecf7030fa..28b6b7ae9 100644
--- a/navalplanner-webapp/src/main/java/org/navalplanner/ws/common/api/LabelDTO.java
+++ b/navalplanner-webapp/src/main/java/org/navalplanner/ws/common/api/LabelReferenceDTO.java
@@ -26,25 +26,21 @@ import javax.xml.bind.annotation.XmlRootElement;
 import org.navalplanner.business.labels.entities.Label;
 
 /**
- * DTO for {@link Label} entity.
+ * DTO for references to {@link Label} entities.
  *
  * @author Manuel Rego Casasnovas <mrego@igalia.com>
  */
 @XmlRootElement(name = "label")
-public class LabelDTO {
+public class LabelReferenceDTO {
 
     @XmlAttribute
-    public String name;
+    public String code;
 
-    @XmlAttribute
-    public String type;
-
-    public LabelDTO() {
+    public LabelReferenceDTO() {
     }
 
-    public LabelDTO(String name, String type) {
-        this.name = name;
-        this.type = type;
+    public LabelReferenceDTO(String code) {
+        this.code = code;
     }
 
 }
diff --git a/navalplanner-webapp/src/main/java/org/navalplanner/ws/common/api/OrderDTO.java b/navalplanner-webapp/src/main/java/org/navalplanner/ws/common/api/OrderDTO.java
index 02a87bff3..c539fb8a4 100644
--- a/navalplanner-webapp/src/main/java/org/navalplanner/ws/common/api/OrderDTO.java
+++ b/navalplanner-webapp/src/main/java/org/navalplanner/ws/common/api/OrderDTO.java
@@ -48,7 +48,7 @@ public class OrderDTO extends OrderLineGroupDTO {
     }
 
     public OrderDTO(String name, String code, Date initDate, Date deadline,
-            String description, Set<LabelDTO> labels,
+            String description, Set<LabelReferenceDTO> labels,
             Set<MaterialAssignmentDTO> materialAssignments,
             Set<AdvanceMeasurementDTO> advanceMeasurements,
             Set<CriterionRequirementDTO> criterionRequirements,
diff --git a/navalplanner-webapp/src/main/java/org/navalplanner/ws/common/api/OrderElementDTO.java b/navalplanner-webapp/src/main/java/org/navalplanner/ws/common/api/OrderElementDTO.java
index 55213085b..a4132d556 100644
--- a/navalplanner-webapp/src/main/java/org/navalplanner/ws/common/api/OrderElementDTO.java
+++ b/navalplanner-webapp/src/main/java/org/navalplanner/ws/common/api/OrderElementDTO.java
@@ -57,7 +57,7 @@ public class OrderElementDTO {
 
     @XmlElementWrapper(name = "labels")
     @XmlElement(name = "label")
-    public Set<LabelDTO> labels = new HashSet<LabelDTO>();
+    public Set<LabelReferenceDTO> labels = new HashSet<LabelReferenceDTO>();
 
     @XmlElementWrapper(name = "material-assignments")
     @XmlElement(name = "material-assignment")
@@ -77,7 +77,7 @@ public class OrderElementDTO {
     }
 
     public OrderElementDTO(String name, String code, Date initDate,
-            Date deadline, String description, Set<LabelDTO> labels,
+            Date deadline, String description, Set<LabelReferenceDTO> labels,
             Set<MaterialAssignmentDTO> materialAssignments,
             Set<AdvanceMeasurementDTO> advanceMeasurements,
             Set<CriterionRequirementDTO> criterionRequirements) {
diff --git a/navalplanner-webapp/src/main/java/org/navalplanner/ws/common/api/OrderLineDTO.java b/navalplanner-webapp/src/main/java/org/navalplanner/ws/common/api/OrderLineDTO.java
index ac4e9d5be..ce905c0e2 100644
--- a/navalplanner-webapp/src/main/java/org/navalplanner/ws/common/api/OrderLineDTO.java
+++ b/navalplanner-webapp/src/main/java/org/navalplanner/ws/common/api/OrderLineDTO.java
@@ -47,7 +47,7 @@ public class OrderLineDTO extends OrderElementDTO {
     }
 
     public OrderLineDTO(String name, String code, Date initDate, Date deadline,
-            String description, Set<LabelDTO> labels,
+            String description, Set<LabelReferenceDTO> labels,
             Set<MaterialAssignmentDTO> materialAssignments,
             Set<AdvanceMeasurementDTO> advanceMeasurements,
             Set<CriterionRequirementDTO> criterionRequirements,
diff --git a/navalplanner-webapp/src/main/java/org/navalplanner/ws/common/api/OrderLineGroupDTO.java b/navalplanner-webapp/src/main/java/org/navalplanner/ws/common/api/OrderLineGroupDTO.java
index 21242c3a5..206f6020b 100644
--- a/navalplanner-webapp/src/main/java/org/navalplanner/ws/common/api/OrderLineGroupDTO.java
+++ b/navalplanner-webapp/src/main/java/org/navalplanner/ws/common/api/OrderLineGroupDTO.java
@@ -52,7 +52,7 @@ public class OrderLineGroupDTO extends OrderElementDTO {
     }
 
     public OrderLineGroupDTO(String name, String code, Date initDate,
-            Date deadline, String description, Set<LabelDTO> labels,
+            Date deadline, String description, Set<LabelReferenceDTO> labels,
             Set<MaterialAssignmentDTO> materialAssignments,
             Set<AdvanceMeasurementDTO> advanceMeasurements,
             Set<CriterionRequirementDTO> criterionRequirements,
diff --git a/navalplanner-webapp/src/main/java/org/navalplanner/ws/common/impl/LabelConverter.java b/navalplanner-webapp/src/main/java/org/navalplanner/ws/common/impl/LabelConverter.java
deleted file mode 100644
index c5d709634..000000000
--- a/navalplanner-webapp/src/main/java/org/navalplanner/ws/common/impl/LabelConverter.java
+++ /dev/null
@@ -1,103 +0,0 @@
-/*
- * This file is part of ###PROJECT_NAME###
- *
- * Copyright (C) 2009 Fundación para o Fomento da Calidade Industrial e
- *                    Desenvolvemento Tecnolóxico de Galicia
- *
- * This program is free software: you can redistribute it and/or modify
- * it under the terms of the GNU Affero General Public License as published by
- * the Free Software Foundation, either version 3 of the License, or
- * (at your option) any later version.
- *
- * This program is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- * GNU Affero General Public License for more details.
- *
- * You should have received a copy of the GNU Affero General Public License
- * along with this program.  If not, see <http://www.gnu.org/licenses/>.
- */
-
-package org.navalplanner.ws.common.impl;
-
-import java.util.HashSet;
-import java.util.Set;
-
-import org.hibernate.NonUniqueResultException;
-import org.navalplanner.business.common.Registry;
-import org.navalplanner.business.common.exceptions.InstanceNotFoundException;
-import org.navalplanner.business.labels.entities.Label;
-import org.navalplanner.business.labels.entities.LabelType;
-import org.navalplanner.ws.common.api.LabelDTO;
-
-/**
- * Converter from/to {@link Label} entities to/from DTOs.
- *
- * @author Manuel Rego Casasnovas <mrego@igalia.com>
- */
-public final class LabelConverter {
-
-    private LabelConverter() {
-    }
-
-    public final static LabelDTO toDTO(Label label) {
-        return new LabelDTO(label.getName(), label.getType().getName());
-    }
-
-    public final static Label forceToEntity(LabelDTO labelDTO) {
-        LabelType labelType = null;
-        try {
-            labelType = Registry.getLabelTypeDAO().findUniqueByName(
-                    labelDTO.type);
-        } catch (NonUniqueResultException e) {
-            throw new RuntimeException(e);
-        } catch (InstanceNotFoundException e) {
-            labelType = LabelType.create(labelDTO.type);
-            /*
-             * "validate" method avoids that "labelType" goes to the Hibernate's
-             * session if "labelType" is not valid.
-             */
-            labelType.validate();
-            Registry.getLabelTypeDAO().save(labelType);
-        }
-
-        Label label = Registry.getLabelDAO().findByNameAndType(labelDTO.name,
-                labelType);
-        if (label == null) {
-            label = Label.create(labelDTO.name);
-            label.setType(labelType);
-        }
-
-        return label;
-    }
-
-    public static Set<Label> toEntity(Set<LabelDTO> labels)
-            throws InstanceNotFoundException {
-        Set<Label> result = new HashSet<Label>();
-        for (LabelDTO labelDTO : labels) {
-            result.add(toEntity(labelDTO));
-        }
-        return result;
-    }
-
-    public final static Label toEntity(LabelDTO labelDTO)
-            throws InstanceNotFoundException {
-        LabelType labelType = null;
-        try {
-            labelType = Registry.getLabelTypeDAO().findUniqueByName(
-                    labelDTO.type);
-        } catch (NonUniqueResultException e) {
-            throw new RuntimeException(e);
-        }
-
-        Label label = Registry.getLabelDAO().findByNameAndType(labelDTO.name,
-                labelType);
-        if (label == null) {
-            throw new InstanceNotFoundException(labelDTO.name, Label.class
-                    .getName());
-        }
-
-        return label;
-    }
-
-}
\ No newline at end of file
diff --git a/navalplanner-webapp/src/main/java/org/navalplanner/ws/common/impl/LabelReferenceConverter.java b/navalplanner-webapp/src/main/java/org/navalplanner/ws/common/impl/LabelReferenceConverter.java
new file mode 100644
index 000000000..b92d75b18
--- /dev/null
+++ b/navalplanner-webapp/src/main/java/org/navalplanner/ws/common/impl/LabelReferenceConverter.java
@@ -0,0 +1,65 @@
+/*
+ * This file is part of ###PROJECT_NAME###
+ *
+ * Copyright (C) 2009 Fundación para o Fomento da Calidade Industrial e
+ *                    Desenvolvemento Tecnolóxico de Galicia
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+package org.navalplanner.ws.common.impl;
+
+import java.util.HashSet;
+import java.util.Set;
+
+import org.navalplanner.business.common.Registry;
+import org.navalplanner.business.common.exceptions.InstanceNotFoundException;
+import org.navalplanner.business.labels.entities.Label;
+import org.navalplanner.ws.common.api.LabelReferenceDTO;
+
+/**
+ * Converter from/to {@link Label} entities to/from reference DTOs.
+ *
+ * @author Manuel Rego Casasnovas <mrego@igalia.com>
+ */
+public final class LabelReferenceConverter {
+
+    private LabelReferenceConverter() {
+    }
+
+    public final static LabelReferenceDTO toDTO(Label label) {
+        return new LabelReferenceDTO(label.getCode());
+    }
+
+    public static Set<Label> toEntity(Set<LabelReferenceDTO> labels)
+            throws InstanceNotFoundException {
+        Set<Label> result = new HashSet<Label>();
+        for (LabelReferenceDTO labelReferenceDTO : labels) {
+            result.add(toEntity(labelReferenceDTO));
+        }
+        return result;
+    }
+
+    public final static Label toEntity(LabelReferenceDTO labelReferenceDTO)
+            throws InstanceNotFoundException {
+        // FIXME review if this check could be moved to findByCode at
+        // IntegrationEntityDAO
+        if (labelReferenceDTO.code == null) {
+            throw new InstanceNotFoundException(null, Label.class.getName());
+        }
+
+        return Registry.getLabelDAO().findByCode(labelReferenceDTO.code);
+    }
+
+}
diff --git a/navalplanner-webapp/src/main/java/org/navalplanner/ws/common/impl/OrderElementConverter.java b/navalplanner-webapp/src/main/java/org/navalplanner/ws/common/impl/OrderElementConverter.java
index 6ddfb40ca..63dba6414 100644
--- a/navalplanner-webapp/src/main/java/org/navalplanner/ws/common/impl/OrderElementConverter.java
+++ b/navalplanner-webapp/src/main/java/org/navalplanner/ws/common/impl/OrderElementConverter.java
@@ -60,7 +60,7 @@ import org.navalplanner.ws.common.api.DirectCriterionRequirementDTO;
 import org.navalplanner.ws.common.api.HoursGroupDTO;
 import org.navalplanner.ws.common.api.IncompatibleTypeException;
 import org.navalplanner.ws.common.api.IndirectCriterionRequirementDTO;
-import org.navalplanner.ws.common.api.LabelDTO;
+import org.navalplanner.ws.common.api.LabelReferenceDTO;
 import org.navalplanner.ws.common.api.MaterialAssignmentDTO;
 import org.navalplanner.ws.common.api.OrderDTO;
 import org.navalplanner.ws.common.api.OrderElementDTO;
@@ -86,10 +86,10 @@ public final class OrderElementConverter {
         Date deadline = orderElement.getDeadline();
         String description = orderElement.getDescription();
 
-        Set<LabelDTO> labels = new HashSet<LabelDTO>();
+        Set<LabelReferenceDTO> labels = new HashSet<LabelReferenceDTO>();
         if (configuration.isLabels()) {
             for (Label label : orderElement.getLabels()) {
-                labels.add(LabelConverter.toDTO(label));
+                labels.add(LabelReferenceConverter.toDTO(label));
             }
         }
 
@@ -224,7 +224,8 @@ public final class OrderElementConverter {
     }
 
     public final static OrderElement toEntity(OrderElementDTO orderElementDTO,
-            ConfigurationOrderElementConverter configuration) {
+            ConfigurationOrderElementConverter configuration)
+            throws InstanceNotFoundException {
         OrderElement orderElement = toEntityExceptCriterionRequirements(
                 orderElementDTO, configuration);
         if (configuration.isCriterionRequirements()) {
@@ -314,7 +315,8 @@ public final class OrderElementConverter {
 
     private final static OrderElement toEntityExceptCriterionRequirements(
             OrderElementDTO orderElementDTO,
-            ConfigurationOrderElementConverter configuration) {
+            ConfigurationOrderElementConverter configuration)
+            throws InstanceNotFoundException {
         OrderElement orderElement;
 
         if (orderElementDTO instanceof OrderLineDTO) {
@@ -369,8 +371,8 @@ public final class OrderElementConverter {
         orderElement.setDescription(orderElementDTO.description);
 
         if (configuration.isLabels()) {
-            for (LabelDTO labelDTO : orderElementDTO.labels) {
-                orderElement.addLabel(LabelConverter.forceToEntity(labelDTO));
+            for (LabelReferenceDTO labelDTO : orderElementDTO.labels) {
+                orderElement.addLabel(LabelReferenceConverter.toEntity(labelDTO));
             }
         }
 
@@ -454,7 +456,7 @@ public final class OrderElementConverter {
     public final static void update(OrderElement orderElement,
             OrderElementDTO orderElementDTO,
             ConfigurationOrderElementConverter configuration)
-            throws IncompatibleTypeException {
+            throws IncompatibleTypeException, InstanceNotFoundException {
         updateExceptCriterionRequirements(orderElement, orderElementDTO,
                 configuration);
         if (configuration.isCriterionRequirements()) {
@@ -465,7 +467,7 @@ public final class OrderElementConverter {
     private final static void updateExceptCriterionRequirements(
             OrderElement orderElement, OrderElementDTO orderElementDTO,
             ConfigurationOrderElementConverter configuration)
-            throws IncompatibleTypeException {
+            throws IncompatibleTypeException, InstanceNotFoundException {
 
         if (orderElementDTO instanceof OrderLineDTO) {
             if (!(orderElement instanceof OrderLine)) {
@@ -534,9 +536,9 @@ public final class OrderElementConverter {
         }
 
         if (configuration.isLabels()) {
-            for (LabelDTO labelDTO : orderElementDTO.labels) {
-                if (!orderElement.containsLabel(labelDTO.name, labelDTO.type)) {
-                    orderElement.addLabel(LabelConverter.forceToEntity(labelDTO));
+            for (LabelReferenceDTO labelDTO : orderElementDTO.labels) {
+                if (!orderElement.containsLabel(labelDTO.code)) {
+                    orderElement.addLabel(LabelReferenceConverter.toEntity(labelDTO));
                 }
             }
         }
diff --git a/navalplanner-webapp/src/main/java/org/navalplanner/ws/orders/impl/OrderElementServiceREST.java b/navalplanner-webapp/src/main/java/org/navalplanner/ws/orders/impl/OrderElementServiceREST.java
index 83fc53ffb..9e226fefd 100644
--- a/navalplanner-webapp/src/main/java/org/navalplanner/ws/orders/impl/OrderElementServiceREST.java
+++ b/navalplanner-webapp/src/main/java/org/navalplanner/ws/orders/impl/OrderElementServiceREST.java
@@ -94,6 +94,10 @@ public class OrderElementServiceREST implements IOrderElementService {
             instanceConstraintViolationsDTO = ConstraintViolationConverter
                     .toDTO(Util.generateInstanceId(1, orderDTO.code), e
                             .getInvalidValues());
+        } catch (InstanceNotFoundException e) {
+            instanceConstraintViolationsDTO = InstanceConstraintViolationsDTO
+                    .create(Util.generateInstanceId(1, orderDTO.code), e
+                            .getMessage());
         }
 
         if (instanceConstraintViolationsDTO != null) {
diff --git a/navalplanner-webapp/src/main/java/org/navalplanner/ws/subcontract/impl/SubcontractServiceREST.java b/navalplanner-webapp/src/main/java/org/navalplanner/ws/subcontract/impl/SubcontractServiceREST.java
index e01bf8bf6..8423220b7 100644
--- a/navalplanner-webapp/src/main/java/org/navalplanner/ws/subcontract/impl/SubcontractServiceREST.java
+++ b/navalplanner-webapp/src/main/java/org/navalplanner/ws/subcontract/impl/SubcontractServiceREST.java
@@ -153,6 +153,10 @@ public class SubcontractServiceREST implements ISubcontractService {
             instanceConstraintViolationsDTO = ConstraintViolationConverter
                     .toDTO(Util.generateInstanceId(1, orderElementDTO.code), e
                             .getInvalidValues());
+        } catch (InstanceNotFoundException e) {
+            instanceConstraintViolationsDTO = InstanceConstraintViolationsDTO
+                    .create(Util.generateInstanceId(1, orderElementDTO.code), e
+                            .getMessage());
         }
 
         if (instanceConstraintViolationsDTO != null) {
diff --git a/navalplanner-webapp/src/main/java/org/navalplanner/ws/workreports/api/WorkReportDTO.java b/navalplanner-webapp/src/main/java/org/navalplanner/ws/workreports/api/WorkReportDTO.java
index c2f60c02d..a1476fb49 100644
--- a/navalplanner-webapp/src/main/java/org/navalplanner/ws/workreports/api/WorkReportDTO.java
+++ b/navalplanner-webapp/src/main/java/org/navalplanner/ws/workreports/api/WorkReportDTO.java
@@ -31,7 +31,7 @@ import javax.xml.bind.annotation.XmlRootElement;
 
 import org.navalplanner.business.workreports.entities.WorkReport;
 import org.navalplanner.ws.common.api.IntegrationEntityDTO;
-import org.navalplanner.ws.common.api.LabelDTO;
+import org.navalplanner.ws.common.api.LabelReferenceDTO;
 
 /**
  * DTO for {@link WorkReport} entity.
@@ -57,7 +57,7 @@ public class WorkReportDTO extends IntegrationEntityDTO {
 
     @XmlElementWrapper(name = "label-list")
     @XmlElement(name = "label")
-    public Set<LabelDTO> labels = new HashSet<LabelDTO>();
+    public Set<LabelReferenceDTO> labels = new HashSet<LabelReferenceDTO>();
 
     @XmlElementWrapper(name = "text-field-list")
     @XmlElement(name = "text-field")
@@ -71,7 +71,7 @@ public class WorkReportDTO extends IntegrationEntityDTO {
     }
 
     public WorkReportDTO(String code, String workReportType, Date date,
-            String resource, String orderElement, Set<LabelDTO> labels,
+            String resource, String orderElement, Set<LabelReferenceDTO> labels,
             Set<DescriptionValueDTO> descriptionValues,
             Set<WorkReportLineDTO> workReportLines) {
         super(code);
diff --git a/navalplanner-webapp/src/main/java/org/navalplanner/ws/workreports/api/WorkReportLineDTO.java b/navalplanner-webapp/src/main/java/org/navalplanner/ws/workreports/api/WorkReportLineDTO.java
index 844cc559e..834534674 100644
--- a/navalplanner-webapp/src/main/java/org/navalplanner/ws/workreports/api/WorkReportLineDTO.java
+++ b/navalplanner-webapp/src/main/java/org/navalplanner/ws/workreports/api/WorkReportLineDTO.java
@@ -31,7 +31,7 @@ import javax.xml.bind.annotation.XmlRootElement;
 
 import org.navalplanner.business.workreports.entities.WorkReportLine;
 import org.navalplanner.ws.common.api.IntegrationEntityDTO;
-import org.navalplanner.ws.common.api.LabelDTO;
+import org.navalplanner.ws.common.api.LabelReferenceDTO;
 
 /**
  * DTO for {@link WorkReportLine} entity.
@@ -66,7 +66,7 @@ public class WorkReportLineDTO extends IntegrationEntityDTO {
 
     @XmlElementWrapper(name = "label-list")
     @XmlElement(name = "label")
-    public Set<LabelDTO> labels = new HashSet<LabelDTO>();
+    public Set<LabelReferenceDTO> labels = new HashSet<LabelReferenceDTO>();
 
     @XmlElementWrapper(name = "text-field-list")
     @XmlElement(name = "text-field")
@@ -77,7 +77,7 @@ public class WorkReportLineDTO extends IntegrationEntityDTO {
 
     public WorkReportLineDTO(String code, Date date, String resource,
             String orderElement, String typeOfWorkHours, Date clockStart,
-            Date clockFinish, Integer numHours, Set<LabelDTO> labels,
+            Date clockFinish, Integer numHours, Set<LabelReferenceDTO> labels,
             Set<DescriptionValueDTO> descriptionValues) {
         super(code);
         this.date = date;
diff --git a/navalplanner-webapp/src/main/java/org/navalplanner/ws/workreports/impl/WorkReportConverter.java b/navalplanner-webapp/src/main/java/org/navalplanner/ws/workreports/impl/WorkReportConverter.java
index b9f4f8f91..cee5b40d4 100644
--- a/navalplanner-webapp/src/main/java/org/navalplanner/ws/workreports/impl/WorkReportConverter.java
+++ b/navalplanner-webapp/src/main/java/org/navalplanner/ws/workreports/impl/WorkReportConverter.java
@@ -32,7 +32,7 @@ import org.navalplanner.business.workreports.entities.WorkReport;
 import org.navalplanner.business.workreports.entities.WorkReportLine;
 import org.navalplanner.business.workreports.entities.WorkReportType;
 import org.navalplanner.business.workreports.valueobjects.DescriptionValue;
-import org.navalplanner.ws.common.impl.LabelConverter;
+import org.navalplanner.ws.common.impl.LabelReferenceConverter;
 import org.navalplanner.ws.workreports.api.DescriptionValueDTO;
 import org.navalplanner.ws.workreports.api.WorkReportDTO;
 import org.navalplanner.ws.workreports.api.WorkReportLineDTO;
@@ -77,7 +77,7 @@ public final class WorkReportConverter {
         }
 
         if (workReportDTO.labels != null) {
-            workReport.setLabels(LabelConverter.toEntity(workReportDTO.labels));
+            workReport.setLabels(LabelReferenceConverter.toEntity(workReportDTO.labels));
         }
 
         if (workReportDTO.descriptionValues != null) {
@@ -124,7 +124,7 @@ public final class WorkReportConverter {
         }
 
         if (workReportLineDTO.labels != null) {
-            workReportLine.setLabels(LabelConverter
+            workReportLine.setLabels(LabelReferenceConverter
                     .toEntity(workReportLineDTO.labels));
         }
 
diff --git a/navalplanner-webapp/src/test/java/org/navalplanner/web/test/ws/orders/OrderElementServiceTest.java b/navalplanner-webapp/src/test/java/org/navalplanner/web/test/ws/orders/OrderElementServiceTest.java
index 180ef8400..b296cbfce 100644
--- a/navalplanner-webapp/src/test/java/org/navalplanner/web/test/ws/orders/OrderElementServiceTest.java
+++ b/navalplanner-webapp/src/test/java/org/navalplanner/web/test/ws/orders/OrderElementServiceTest.java
@@ -25,7 +25,6 @@ import static org.hamcrest.CoreMatchers.equalTo;
 import static org.hamcrest.CoreMatchers.instanceOf;
 import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertNotNull;
-import static org.junit.Assert.assertNull;
 import static org.junit.Assert.assertThat;
 import static org.junit.Assert.assertTrue;
 import static org.junit.Assert.fail;
@@ -40,12 +39,14 @@ import java.util.HashSet;
 import java.util.List;
 import java.util.Set;
 import java.util.SortedSet;
+import java.util.UUID;
 
 import javax.annotation.Resource;
 
 import org.hamcrest.BaseMatcher;
 import org.hamcrest.Description;
 import org.hamcrest.Matcher;
+import org.hibernate.SessionFactory;
 import org.joda.time.LocalDate;
 import org.junit.Before;
 import org.junit.Test;
@@ -54,11 +55,14 @@ import org.navalplanner.business.IDataBootstrap;
 import org.navalplanner.business.advance.entities.AdvanceMeasurement;
 import org.navalplanner.business.advance.entities.DirectAdvanceAssignment;
 import org.navalplanner.business.common.exceptions.InstanceNotFoundException;
+import org.navalplanner.business.labels.daos.ILabelTypeDAO;
 import org.navalplanner.business.labels.entities.Label;
+import org.navalplanner.business.labels.entities.LabelType;
 import org.navalplanner.business.materials.entities.MaterialAssignment;
 import org.navalplanner.business.orders.daos.IOrderDAO;
 import org.navalplanner.business.orders.daos.IOrderElementDAO;
 import org.navalplanner.business.orders.entities.HoursGroup;
+import org.navalplanner.business.orders.entities.Order;
 import org.navalplanner.business.orders.entities.OrderElement;
 import org.navalplanner.business.orders.entities.OrderLine;
 import org.navalplanner.business.requirements.entities.CriterionRequirement;
@@ -74,7 +78,7 @@ import org.navalplanner.ws.common.api.HoursGroupDTO;
 import org.navalplanner.ws.common.api.IncompatibleTypeException;
 import org.navalplanner.ws.common.api.IndirectCriterionRequirementDTO;
 import org.navalplanner.ws.common.api.InstanceConstraintViolationsDTO;
-import org.navalplanner.ws.common.api.LabelDTO;
+import org.navalplanner.ws.common.api.LabelReferenceDTO;
 import org.navalplanner.ws.common.api.MaterialAssignmentDTO;
 import org.navalplanner.ws.common.api.OrderDTO;
 import org.navalplanner.ws.common.api.OrderLineDTO;
@@ -127,6 +131,30 @@ public class OrderElementServiceTest {
     @Autowired
     private IOrderElementDAO orderElementDAO;
 
+    @Autowired
+    private ILabelTypeDAO labelTypeDAO;
+
+    @Autowired
+    private SessionFactory sessionFactory;
+
+    private Label givenLabelStored() {
+        Label label = Label.create("label-name-" + UUID.randomUUID());
+
+        LabelType labelType = LabelType.create("label-type-"
+                + UUID.randomUUID());
+        labelType.addLabel(label);
+
+        labelTypeDAO.save(labelType);
+        labelTypeDAO.flush();
+        sessionFactory.getCurrentSession().evict(labelType);
+        sessionFactory.getCurrentSession().evict(label);
+
+        labelType.dontPoseAsTransientObjectAnymore();
+        label.dontPoseAsTransientObjectAnymore();
+
+        return label;
+    }
+
     @Test
     public void invalidOrderWithoutAttributes() {
         int previous = orderDAO.getOrders().size();
@@ -483,8 +511,8 @@ public class OrderElementServiceTest {
         orderDTO.code = "order-code";
         orderDTO.initDate = new Date();
 
-        LabelDTO labelDTO = new LabelDTO();
-        orderDTO.labels.add(labelDTO);
+        LabelReferenceDTO labelReferenceDTO = new LabelReferenceDTO();
+        orderDTO.labels.add(labelReferenceDTO);
 
         List<InstanceConstraintViolationsDTO> instanceConstraintViolationsList = orderElementService
                 .addOrder(orderDTO).instanceConstraintViolationsList;
@@ -492,36 +520,7 @@ public class OrderElementServiceTest {
 
         List<ConstraintViolationDTO> constraintViolations = instanceConstraintViolationsList
                 .get(0).constraintViolations;
-        // Mandatory fields: material, units, unitPrice
         assertThat(constraintViolations.size(), equalTo(1));
-        assertThat(constraintViolations.get(0).fieldName,
-                equalTo("LabelType::name"));
-
-        assertThat(orderDAO.getOrders().size(), equalTo(previous));
-    }
-
-    @Test
-    public void orderWithInvalidLabelWithoutName() {
-        int previous = orderDAO.getOrders().size();
-
-        OrderDTO orderDTO = new OrderDTO();
-        orderDTO.name = "Order name";
-        orderDTO.code = "order-code";
-        orderDTO.initDate = new Date();
-
-        LabelDTO labelDTO = new LabelDTO();
-        labelDTO.type = "Label type";
-        orderDTO.labels.add(labelDTO);
-
-        List<InstanceConstraintViolationsDTO> instanceConstraintViolationsList = orderElementService
-                .addOrder(orderDTO).instanceConstraintViolationsList;
-        assertThat(instanceConstraintViolationsList.size(), equalTo(1));
-
-        List<ConstraintViolationDTO> constraintViolations = instanceConstraintViolationsList
-                .get(0).constraintViolations;
-        // Mandatory fields: material, units, unitPrice
-        assertThat(constraintViolations.size(), equalTo(1));
-        assertThat(constraintViolations.get(0).fieldName, mustEnd("name"));
 
         assertThat(orderDAO.getOrders().size(), equalTo(previous));
     }
@@ -536,10 +535,9 @@ public class OrderElementServiceTest {
         orderDTO.code = code;
         orderDTO.initDate = new Date();
 
-        LabelDTO labelDTO = new LabelDTO();
-        labelDTO.name = "Label name";
-        labelDTO.type = "Label type";
-        orderDTO.labels.add(labelDTO);
+        LabelReferenceDTO labelReferenceDTO = new LabelReferenceDTO();
+        labelReferenceDTO.code = givenLabelStored().getCode();
+        orderDTO.labels.add(labelReferenceDTO);
 
         List<InstanceConstraintViolationsDTO> instanceConstraintViolationsList = orderElementService
                 .addOrder(orderDTO).instanceConstraintViolationsList;
@@ -550,7 +548,7 @@ public class OrderElementServiceTest {
     }
 
     @Test
-    public void orderWithLabelRepeatedInTheSameBranch() {
+    public void orderWithLabelRepeatedInTheSameBranchIsNotAddedTwice() {
         int previous = orderDAO.getOrders().size();
 
         OrderDTO orderDTO = new OrderDTO();
@@ -558,10 +556,9 @@ public class OrderElementServiceTest {
         orderDTO.code = "order-code";
         orderDTO.initDate = new Date();
 
-        LabelDTO labelDTO = new LabelDTO();
-        labelDTO.name = "Label name";
-        labelDTO.type = "Label type";
-        orderDTO.labels.add(labelDTO);
+        LabelReferenceDTO labelReferenceDTO = new LabelReferenceDTO();
+        labelReferenceDTO.code = givenLabelStored().getCode();
+        orderDTO.labels.add(labelReferenceDTO);
 
         OrderLineDTO orderLineDTO = new OrderLineDTO();
         orderLineDTO.name = "Order line";
@@ -570,20 +567,22 @@ public class OrderElementServiceTest {
                 ResourceEnumDTO.WORKER, 1000,
                 new HashSet<CriterionRequirementDTO>());
         orderLineDTO.hoursGroups.add(hoursGroupDTO);
-        orderLineDTO.labels.add(labelDTO);
+        orderLineDTO.labels.add(labelReferenceDTO);
         orderDTO.children.add(orderLineDTO);
 
         List<InstanceConstraintViolationsDTO> instanceConstraintViolationsList = orderElementService
                 .addOrder(orderDTO).instanceConstraintViolationsList;
-        assertThat(instanceConstraintViolationsList.size(), equalTo(1));
+        assertThat(instanceConstraintViolationsList.size(), equalTo(0));
 
-        List<ConstraintViolationDTO> constraintViolations = instanceConstraintViolationsList
-                .get(0).constraintViolations;
-        // Mandatory fields: checkConstraintLabelNotRepeatedInTheSameBranch
-        assertThat(constraintViolations.size(), equalTo(1));
-        assertNull(constraintViolations.get(0).fieldName);
+        assertThat(orderDAO.getOrders().size(), equalTo(previous + 1));
 
-        assertThat(orderDAO.getOrders().size(), equalTo(previous));
+        Order order = orderDAO.getOrders().get(previous);
+        assertThat(order.getLabels().size(), equalTo(1));
+        assertThat(order.getLabels().iterator().next().getCode(),
+                equalTo(labelReferenceDTO.code));
+
+        OrderElement orderElement = order.getChildren().get(0);
+        assertThat(orderElement.getLabels().size(), equalTo(0));
     }
 
     @Test
@@ -602,8 +601,9 @@ public class OrderElementServiceTest {
         orderDTO.code = code;
         orderDTO.initDate = new Date();
 
-        LabelDTO labelDTO = new LabelDTO("Label name", "Label type");
-        orderDTO.labels.add(labelDTO);
+        LabelReferenceDTO labelReferenceDTO = new LabelReferenceDTO(givenLabelStored()
+                .getCode());
+        orderDTO.labels.add(labelReferenceDTO);
 
         List<InstanceConstraintViolationsDTO> instanceConstraintViolationsList = orderElementService
                 .addOrder(orderDTO).instanceConstraintViolationsList;
@@ -613,8 +613,9 @@ public class OrderElementServiceTest {
         assertNotNull(orderElement);
         assertThat(orderElement.getLabels().size(), equalTo(1));
 
-        LabelDTO labelDTO2 = new LabelDTO("Label name2", "Label type");
-        orderDTO.labels.add(labelDTO2);
+        LabelReferenceDTO labelReferenceDTO2 = new LabelReferenceDTO(givenLabelStored()
+                .getCode());
+        orderDTO.labels.add(labelReferenceDTO2);
         instanceConstraintViolationsList = orderElementService
                 .updateOrder(orderDTO).instanceConstraintViolationsList;
         assertThat(instanceConstraintViolationsList.size(), equalTo(0));
@@ -622,9 +623,8 @@ public class OrderElementServiceTest {
         orderElement = orderElementDAO.findUniqueByCode(code);
         assertThat(orderElement.getLabels().size(), equalTo(2));
         for (Label label : orderElement.getLabels()) {
-            assertThat(label.getName(), anyOf(equalTo("Label name"),
-                    equalTo("Label name2")));
-            assertThat(label.getType().getName(), equalTo("Label type"));
+            assertThat(label.getCode(), anyOf(equalTo(labelReferenceDTO.code),
+                    equalTo(labelReferenceDTO2.code)));
         }
     }