diff --git a/libreplan-business/src/main/java/org/libreplan/business/common/entities/AppProperties.java b/libreplan-business/src/main/java/org/libreplan/business/common/entities/AppProperties.java
index a5b977564..7c048051f 100644
--- a/libreplan-business/src/main/java/org/libreplan/business/common/entities/AppProperties.java
+++ b/libreplan-business/src/main/java/org/libreplan/business/common/entities/AppProperties.java
@@ -19,10 +19,22 @@
 
 package org.libreplan.business.common.entities;
 
+import org.hibernate.validator.NotNull;
 import org.libreplan.business.common.BaseEntity;
 
 /**
- * AppProperties Entity
+ * AppProperties Entity, represents application configuration parameters.
+ *
+ * This property can be used by all applications who needs simple name-value
+ * pair configurations. It consists the following properties:
+ * <ul>
+ * <li>majorId: an indication for some large piece of functionality like "jira"
+ * for "jira-connector"</li>
+ * <li>minorId: used for sub module within this majorId. It can be null if not
+ * used</li>
+ * <li>propertyName: holder for the name of a property</li>
+ * <li>propertyValue: holder for the value of a property</li>
+ * </ul>
  *
  * @author Miciele Ghiorghis <m.ghiorghis@antoniusziekenhuis.nl>
  */
@@ -33,8 +45,11 @@ public class AppProperties extends BaseEntity {
     }
 
     private String majorId;
+
     private String minorId;
+
     private String propertyName;
+
     private String propertyValue;
 
     /**
@@ -43,6 +58,7 @@ public class AppProperties extends BaseEntity {
     protected AppProperties() {
     }
 
+    @NotNull(message = "majorId not specified")
     public String getMajorId() {
         return majorId;
     }
@@ -59,6 +75,7 @@ public class AppProperties extends BaseEntity {
         this.minorId = minorId;
     }
 
+    @NotNull(message = "property name not specified")
     public String getPropertyName() {
         return propertyName;
     }
@@ -67,6 +84,7 @@ public class AppProperties extends BaseEntity {
         this.propertyName = propertyName;
     }
 
+    @NotNull(message = "property value not specified")
     public String getPropertyValue() {
         return propertyValue;
     }
diff --git a/libreplan-business/src/main/java/org/libreplan/business/common/entities/JobSchedulerConfiguration.java b/libreplan-business/src/main/java/org/libreplan/business/common/entities/JobSchedulerConfiguration.java
index a0938dc7a..ccee32606 100644
--- a/libreplan-business/src/main/java/org/libreplan/business/common/entities/JobSchedulerConfiguration.java
+++ b/libreplan-business/src/main/java/org/libreplan/business/common/entities/JobSchedulerConfiguration.java
@@ -19,10 +19,17 @@
 
 package org.libreplan.business.common.entities;
 
+import org.hibernate.validator.NotNull;
 import org.libreplan.business.common.BaseEntity;
 
 /**
- * JobSchedulerConfiguration entity
+ * JobSchedulerConfiguration entity, represents parameters for the jobs to be
+ * scheduled. This entity is used by the <code>SchedulerManager</code> to
+ * schedule jobs and in UI to show the scheduler status.
+ *
+ * The <code>jobGroup</code> and <code>jobName</code> together forms a job key
+ * and non of the fields must be null. Moreover it should contain a valid
+ * <code>cronExpression</code>
  *
  * @author Miciele Ghiorghis <m.ghiorghis@antoniusziekenhuis.nl>
  */
@@ -39,12 +46,18 @@ public class JobSchedulerConfiguration extends BaseEntity {
     }
 
     private String jobGroup;
+
     private String jobName;
+
     private String triggerGroup;
+
     private String triggerName;
+
     private String cronExpression;
+
     private String jobClassName;
 
+    @NotNull(message = "job group not specified")
     public String getJobGroup() {
         return jobGroup;
     }
@@ -53,6 +66,7 @@ public class JobSchedulerConfiguration extends BaseEntity {
         this.jobGroup = jobGroup;
     }
 
+    @NotNull(message = "job name not specified")
     public String getJobName() {
         return jobName;
     }
@@ -61,6 +75,7 @@ public class JobSchedulerConfiguration extends BaseEntity {
         this.jobName = jobName;
     }
 
+    @NotNull(message = "trigger group not specified")
     public String getTriggerGroup() {
         return triggerGroup;
     }
@@ -69,6 +84,7 @@ public class JobSchedulerConfiguration extends BaseEntity {
         this.triggerGroup = triggerGroup;
     }
 
+    @NotNull(message = "trigger name not specified")
     public String getTriggerName() {
         return triggerName;
     }
@@ -77,6 +93,7 @@ public class JobSchedulerConfiguration extends BaseEntity {
         this.triggerName = triggerName;
     }
 
+    @NotNull(message = "cron expression not specified")
     public String getCronExpression() {
         return cronExpression;
     }
@@ -85,6 +102,7 @@ public class JobSchedulerConfiguration extends BaseEntity {
         this.cronExpression = cronExpression;
     }
 
+    @NotNull(message = "job class name not specified")
     public String getJobClassName() {
         return jobClassName;
     }
diff --git a/libreplan-business/src/main/resources/org/libreplan/business/common/entities/AppProperties.hbm.xml b/libreplan-business/src/main/resources/org/libreplan/business/common/entities/AppProperties.hbm.xml
index 185cc5a58..789b78d0f 100644
--- a/libreplan-business/src/main/resources/org/libreplan/business/common/entities/AppProperties.hbm.xml
+++ b/libreplan-business/src/main/resources/org/libreplan/business/common/entities/AppProperties.hbm.xml
@@ -15,7 +15,7 @@
         <property name="majorId" column="major_id" not-null="true" />
         <property name="minorId" column="minor_id" />
         <property name="propertyName" column="property_name" not-null="true"/>
-        <property name="propertyValue" column="property_value" />
+        <property name="propertyValue" column="property_value" not-null="true"/>
     </class>
 
 </hibernate-mapping>
diff --git a/libreplan-webapp/src/main/java/org/libreplan/importers/RosterException.java b/libreplan-webapp/src/main/java/org/libreplan/importers/RosterException.java
index 29ac804d0..43de84ea0 100644
--- a/libreplan-webapp/src/main/java/org/libreplan/importers/RosterException.java
+++ b/libreplan-webapp/src/main/java/org/libreplan/importers/RosterException.java
@@ -71,6 +71,22 @@ public class RosterException {
     /**
      * updates the <code>exceptionType</code> and <code>effortDuration</code>
      *
+     * In Tim you can divide your exception day in different
+     * <code>exceptionType</code>, for example on Monday:
+     * <ul>
+     * <li>4 hours RESOURCE_HOLIDAY</li>
+     * <li>2 hours STRIKE</li>
+     * <li>2 hours BANK_HOLIDAY</li>
+     * </ul>
+     *
+     * But Libreplan allows only one <code>exceptionType</code> per day.
+     *
+     * In order to store different <code>exceptionTypes</code> per day as one
+     * <code>exceptionType</code>, this method gets the
+     * <code>exceptionType</code> from the <code>rosterDTO</code> with the
+     * highest duration, in this example RESOURCE_HOLIDAY as a valid exception
+     * type, but the total duration is the sum of all these exception types
+     *
      * @param rosterExceptionItem
      *            the rosterException item
      * @param rosterDTOs