diff --git a/navalplanner-business/src/main/java/org/navalplanner/business/calendars/entities/ResourceCalendar.java b/navalplanner-business/src/main/java/org/navalplanner/business/calendars/entities/ResourceCalendar.java
index 996682d40..0857b6bf5 100644
--- a/navalplanner-business/src/main/java/org/navalplanner/business/calendars/entities/ResourceCalendar.java
+++ b/navalplanner-business/src/main/java/org/navalplanner/business/calendars/entities/ResourceCalendar.java
@@ -20,6 +20,7 @@
 
 package org.navalplanner.business.calendars.entities;
 
+import org.hibernate.validator.AssertTrue;
 import org.joda.time.LocalDate;
 import org.navalplanner.business.resources.entities.Resource;
 
@@ -65,4 +66,9 @@ public class ResourceCalendar extends BaseCalendar {
         return super.getWorkableHours(date);
     }
 
+    @AssertTrue(message = "Capacity must be a positive integer number")
+    public boolean checkCapacityPositiveIntegerNumber() {
+        return (capacity >= 1);
+    }
+
 }
diff --git a/navalplanner-business/src/main/java/org/navalplanner/business/common/Registry.java b/navalplanner-business/src/main/java/org/navalplanner/business/common/Registry.java
index 2005ecb2a..90589a01b 100644
--- a/navalplanner-business/src/main/java/org/navalplanner/business/common/Registry.java
+++ b/navalplanner-business/src/main/java/org/navalplanner/business/common/Registry.java
@@ -32,6 +32,7 @@ import org.navalplanner.business.orders.daos.IOrderElementDAO;
 import org.navalplanner.business.qualityforms.daos.IQualityFormDAO;
 import org.navalplanner.business.resources.daos.ICriterionTypeDAO;
 import org.navalplanner.business.resources.daos.IMachineDAO;
+import org.navalplanner.business.resources.daos.IWorkerDAO;
 import org.navalplanner.business.users.daos.IProfileDAO;
 import org.navalplanner.business.users.daos.IUserDAO;
 import org.navalplanner.business.workreports.daos.IWorkReportTypeDAO;
@@ -100,6 +101,9 @@ public class Registry {
     @Autowired
     private IOrderElementDAO orderElementDAO;
 
+    @Autowired
+    private IWorkerDAO workerDAO;
+
     private Registry() {
     }
 
@@ -167,4 +171,8 @@ public class Registry {
         return getInstance().orderElementDAO;
     }
 
+    public static IWorkerDAO getWorkerDAO() {
+        return getInstance().workerDAO;
+    }
+
 }
\ No newline at end of file
diff --git a/navalplanner-business/src/main/java/org/navalplanner/business/resources/daos/IWorkerDAO.java b/navalplanner-business/src/main/java/org/navalplanner/business/resources/daos/IWorkerDAO.java
index 6f8abc1c9..5f7146466 100644
--- a/navalplanner-business/src/main/java/org/navalplanner/business/resources/daos/IWorkerDAO.java
+++ b/navalplanner-business/src/main/java/org/navalplanner/business/resources/daos/IWorkerDAO.java
@@ -46,7 +46,7 @@ public interface IWorkerDAO extends IGenericDAO<Worker, Long> {
      *            search worker by name(firstname or surname)/NIF
      *
      */
-    List<Worker> findByNameOrNif(String name);
+    List<Worker> findByNameSubpartOrNifCaseInsensitive(String name);
 
     /**
      * Finds a {@link Worker} with the NIF param that should be unique.
@@ -74,4 +74,38 @@ public interface IWorkerDAO extends IGenericDAO<Worker, Long> {
      */
     List<HoursWorkedPerWorkerDTO> getWorkingHoursPerWorker(List<Worker> workers, Date startingDate, Date endingDate);
 
+    /**
+     * Return list of workers with a particular firstName
+     * @param name
+     *            The string with the name searched
+     * @return The list of {@link Worker} entities found
+     */
+    List<Worker> findByFirstNameCaseInsensitive(String name);
+
+    /**
+     * Return list of workers with a particular firstName when called from
+     * inside an external transaction
+     * @param name
+     *            The string with the name searched
+     * @return The list of {@link Worker} entities found
+     */
+    List<Worker> findByFirstNameAnotherTransactionCaseInsensitive(String name);
+
+    /**
+     * Return list of workers with a particular set of firstName, surname and
+     * nif values
+     * @param firstname
+     *            String value for firstname
+     * @param surname
+     *            String value for surname
+     * @param nif
+     *            String value for nif
+     * @return The list of {@link Worker} entities found
+     */
+    List<Worker> findByFirstNameSecondNameAndNif(String firstname,
+            String surname, String nif);
+
+    List<Worker> findByFirstNameSecondNameAndNifAnotherTransaction(
+            String firstname, String surname, String nif);
+
 }
diff --git a/navalplanner-business/src/main/java/org/navalplanner/business/resources/daos/WorkerDAO.java b/navalplanner-business/src/main/java/org/navalplanner/business/resources/daos/WorkerDAO.java
index fd383c79a..011137ad1 100644
--- a/navalplanner-business/src/main/java/org/navalplanner/business/resources/daos/WorkerDAO.java
+++ b/navalplanner-business/src/main/java/org/navalplanner/business/resources/daos/WorkerDAO.java
@@ -33,6 +33,7 @@ import org.navalplanner.business.resources.entities.Worker;
 import org.springframework.beans.factory.config.BeanDefinition;
 import org.springframework.context.annotation.Scope;
 import org.springframework.stereotype.Repository;
+import org.springframework.transaction.annotation.Propagation;
 import org.springframework.transaction.annotation.Transactional;
 
 /**
@@ -69,15 +70,47 @@ public class WorkerDAO extends GenericDAOHibernate<Worker, Long>
 
     @SuppressWarnings("unchecked")
     @Override
-    public List<Worker> findByNameOrNif(String name) {
+    public List<Worker> findByNameSubpartOrNifCaseInsensitive(String name) {
         String containsName = "%" + name + "%";
-        return getSession().createCriteria(Worker.class).add(
+        return getSession().createCriteria(Worker.class)
+                .add(
                         Restrictions.or(Restrictions.or(Restrictions.ilike(
                                 "firstName", containsName), Restrictions.ilike(
                                 "surname", containsName)), Restrictions.like(
                                 "nif", containsName))).list();
     }
 
+    @SuppressWarnings("unchecked")
+    @Override
+    public List<Worker> findByFirstNameCaseInsensitive(String name) {
+        return getSession().createCriteria(Worker.class).add(
+                Restrictions.ilike("firstName", name)).list();
+    }
+
+    @Override
+    @Transactional(readOnly = true, propagation = Propagation.REQUIRES_NEW)
+    public List<Worker> findByFirstNameAnotherTransactionCaseInsensitive(String name) {
+        return findByFirstNameCaseInsensitive(name);
+    }
+
+    @SuppressWarnings("unchecked")
+    @Override
+    public List<Worker> findByFirstNameSecondNameAndNif(String firstname,
+            String secondname, String nif) {
+        return getSession().createCriteria(Worker.class).add(
+                Restrictions.and(Restrictions.ilike("firstName", firstname),
+                        Restrictions.and(Restrictions.ilike("surname",
+                                secondname), Restrictions.like("nif", nif))))
+                .list();
+    }
+
+    @Override
+    @Transactional(readOnly = true, propagation = Propagation.REQUIRES_NEW)
+    public List<Worker> findByFirstNameSecondNameAndNifAnotherTransaction(
+            String firstname, String secondname, String nif) {
+        return findByFirstNameSecondNameAndNif(firstname, secondname, nif);
+    }
+
     @Override
     @Transactional(readOnly = true)
     public List<HoursWorkedPerWorkerDTO> getWorkingHoursPerWorker(List<Worker> workers, Date startingDate, Date endingDate) {
diff --git a/navalplanner-business/src/main/java/org/navalplanner/business/resources/entities/VirtualWorker.java b/navalplanner-business/src/main/java/org/navalplanner/business/resources/entities/VirtualWorker.java
index c52981625..fe75fd8f7 100644
--- a/navalplanner-business/src/main/java/org/navalplanner/business/resources/entities/VirtualWorker.java
+++ b/navalplanner-business/src/main/java/org/navalplanner/business/resources/entities/VirtualWorker.java
@@ -20,6 +20,11 @@
 
 package org.navalplanner.business.resources.entities;
 
+import java.util.List;
+
+import org.hibernate.validator.AssertTrue;
+import org.navalplanner.business.common.Registry;
+
 
 /**
  * This class models a VirtualWorker.
@@ -67,4 +72,19 @@ public class VirtualWorker extends Worker {
         this.observations = observations;
     }
 
+
+    @AssertTrue(message = "Virtual worker group name must be unique")
+    public boolean checkConstraintUniqueVirtualGroupName() {
+
+        List<Worker> list = Registry.getWorkerDAO()
+                .findByFirstNameAnotherTransactionCaseInsensitive(
+                        this.getFirstName());
+
+        if ((isNewObject() && list.isEmpty()) || list.isEmpty()) {
+            return true;
+        } else {
+            return list.get(0).getId().equals(getId());
+        }
+    }
+
 }
diff --git a/navalplanner-business/src/main/java/org/navalplanner/business/resources/entities/Worker.java b/navalplanner-business/src/main/java/org/navalplanner/business/resources/entities/Worker.java
index c6e8f98f4..71cc961dd 100644
--- a/navalplanner-business/src/main/java/org/navalplanner/business/resources/entities/Worker.java
+++ b/navalplanner-business/src/main/java/org/navalplanner/business/resources/entities/Worker.java
@@ -21,8 +21,12 @@
 package org.navalplanner.business.resources.entities;
 
 
+import java.util.List;
+
+import org.hibernate.validator.AssertTrue;
 import org.hibernate.validator.NotEmpty;
 import org.hibernate.validator.NotNull;
+import org.navalplanner.business.common.Registry;
 
 /**
  * This class models a worker.
@@ -111,4 +115,23 @@ public class Worker extends Resource {
         return !isVirtual();
     }
 
+    @AssertTrue(message = "Worker with the same firstname, surname and nif previously existed")
+    public boolean checkConstraintUniqueFirstName() {
+
+        if (this instanceof VirtualWorker) {
+            return true;
+        }
+
+        List<Worker> list = Registry.getWorkerDAO()
+                .findByFirstNameSecondNameAndNifAnotherTransaction(firstName,
+                        surname, nif);
+
+        if ((isNewObject() && list.isEmpty()) || list.isEmpty()) {
+            return true;
+        } else {
+            return list.get(0).getId().equals(getId());
+        }
+
+    }
+
 }
diff --git a/navalplanner-business/src/main/resources/org/navalplanner/business/calendars/entities/Calendars.hbm.xml b/navalplanner-business/src/main/resources/org/navalplanner/business/calendars/entities/Calendars.hbm.xml
index daea70f70..0b11c901d 100644
--- a/navalplanner-business/src/main/resources/org/navalplanner/business/calendars/entities/Calendars.hbm.xml
+++ b/navalplanner-business/src/main/resources/org/navalplanner/business/calendars/entities/Calendars.hbm.xml
@@ -33,7 +33,7 @@
 
         <joined-subclass name="ResourceCalendar">
             <key column="BASE_CALENDAR_ID" />
-            <property name="capacity" />
+            <property name="capacity" not-null="true" />
         </joined-subclass>
     </class>
 
diff --git a/navalplanner-webapp/src/main/java/org/navalplanner/web/resources/search/ResourceSearchModel.java b/navalplanner-webapp/src/main/java/org/navalplanner/web/resources/search/ResourceSearchModel.java
index fc86955f6..3bc8b6b3a 100644
--- a/navalplanner-webapp/src/main/java/org/navalplanner/web/resources/search/ResourceSearchModel.java
+++ b/navalplanner-webapp/src/main/java/org/navalplanner/web/resources/search/ResourceSearchModel.java
@@ -107,7 +107,7 @@ public class ResourceSearchModel implements IResourceSearchModel {
         if (emptyName) {
             return new ArrayList<Resource>(resourcesMatchingCriterions);
         }
-        Set<Resource> result = intersect(workerDAO.findByNameOrNif(name),
+        Set<Resource> result = intersect(workerDAO.findByNameSubpartOrNifCaseInsensitive(name),
                 resourcesMatchingCriterions);
         result.addAll(intersect(machineDAO.findByNameOrCode(name),
                 resourcesMatchingCriterions));
diff --git a/navalplanner-webapp/src/main/java/org/navalplanner/web/resources/worker/WorkerModel.java b/navalplanner-webapp/src/main/java/org/navalplanner/web/resources/worker/WorkerModel.java
index 261ba70d1..04032a8c1 100644
--- a/navalplanner-webapp/src/main/java/org/navalplanner/web/resources/worker/WorkerModel.java
+++ b/navalplanner-webapp/src/main/java/org/navalplanner/web/resources/worker/WorkerModel.java
@@ -523,7 +523,6 @@ public class WorkerModel implements IWorkerModel {
     public void setCapacity(Integer capacity) {
         if (getCalendar() != null) {
             getCalendar().setCapacity(capacity);
-            System.out.println("not null" + getCalendar().getCapacity());
         }
     }
 
diff --git a/navalplanner-webapp/src/main/webapp/resources/worker/_edition.zul b/navalplanner-webapp/src/main/webapp/resources/worker/_edition.zul
index f38e5ed85..51aabeb7e 100644
--- a/navalplanner-webapp/src/main/webapp/resources/worker/_edition.zul
+++ b/navalplanner-webapp/src/main/webapp/resources/worker/_edition.zul
@@ -62,7 +62,7 @@
                         </row>
                         <row visible="@{controller.isVirtualWorker}">
                             <label value="${i18n:_('Capacity')}" />
-                            <intbox value="@{controller.virtualWorkerCapacity}" width="100px" constraint="no negative,no zero" />
+                            <intbox value="@{controller.virtualWorkerCapacity}" width="100px" constraint="no negative,no zero,no empty" />
                         </row>
                         <row visible="@{controller.isVirtualWorker}">
                             <label value="${i18n:_('Observations')}" />
diff --git a/navalplanner-webapp/src/test/java/org/navalplanner/web/resources/WorkerModelTest.java b/navalplanner-webapp/src/test/java/org/navalplanner/web/resources/WorkerModelTest.java
index 85cfdf627..bd33e0392 100644
--- a/navalplanner-webapp/src/test/java/org/navalplanner/web/resources/WorkerModelTest.java
+++ b/navalplanner-webapp/src/test/java/org/navalplanner/web/resources/WorkerModelTest.java
@@ -71,9 +71,9 @@ public class WorkerModelTest {
         workerModel.save();
     }
 
-    @Test(expected = ValidationException.class)
+    @Test(expected = IllegalStateException.class)
     public void testWorkerInvalid() throws ValidationException,
-            InstanceNotFoundException {
+            InstanceNotFoundException, IllegalStateException {
 
         IResourceDAO resourceDAOMock = createMock(IResourceDAO.class);
         ICriterionDAO criterionServiceMock = createMock(ICriterionDAO.class);