diff --git a/src/main/java/ch/eitchnet/privilege/i18n/AccessDeniedException.java b/src/main/java/ch/eitchnet/privilege/base/AccessDeniedException.java
similarity index 96%
rename from src/main/java/ch/eitchnet/privilege/i18n/AccessDeniedException.java
rename to src/main/java/ch/eitchnet/privilege/base/AccessDeniedException.java
index 818335103..0c8fa5283 100644
--- a/src/main/java/ch/eitchnet/privilege/i18n/AccessDeniedException.java
+++ b/src/main/java/ch/eitchnet/privilege/base/AccessDeniedException.java
@@ -17,7 +17,7 @@
  * along with Privilege.  If not, see <http://www.gnu.org/licenses/>.
  * 
  */
-package ch.eitchnet.privilege.i18n;
+package ch.eitchnet.privilege.base;
 
 /**
  * Exception thrown if access is denied during login, or if a certain privilege is not granted
diff --git a/src/main/java/ch/eitchnet/privilege/i18n/PrivilegeException.java b/src/main/java/ch/eitchnet/privilege/base/PrivilegeException.java
similarity index 97%
rename from src/main/java/ch/eitchnet/privilege/i18n/PrivilegeException.java
rename to src/main/java/ch/eitchnet/privilege/base/PrivilegeException.java
index 0f9fe5111..dc254418a 100644
--- a/src/main/java/ch/eitchnet/privilege/i18n/PrivilegeException.java
+++ b/src/main/java/ch/eitchnet/privilege/base/PrivilegeException.java
@@ -17,7 +17,7 @@
  * along with Privilege.  If not, see <http://www.gnu.org/licenses/>.
  * 
  */
-package ch.eitchnet.privilege.i18n;
+package ch.eitchnet.privilege.base;
 
 /**
  * Main {@link RuntimeException} thrown if something goes wrong in Privilege
diff --git a/src/main/java/ch/eitchnet/privilege/handler/DefaultEncryptionHandler.java b/src/main/java/ch/eitchnet/privilege/handler/DefaultEncryptionHandler.java
index 1dbd99a0f..fb614673e 100644
--- a/src/main/java/ch/eitchnet/privilege/handler/DefaultEncryptionHandler.java
+++ b/src/main/java/ch/eitchnet/privilege/handler/DefaultEncryptionHandler.java
@@ -28,9 +28,9 @@ import java.util.Map;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
+import ch.eitchnet.privilege.base.PrivilegeException;
 import ch.eitchnet.privilege.helper.HashHelper;
 import ch.eitchnet.privilege.helper.XmlConstants;
-import ch.eitchnet.privilege.i18n.PrivilegeException;
 
 /**
  * <p>
diff --git a/src/main/java/ch/eitchnet/privilege/handler/DefaultPrivilegeHandler.java b/src/main/java/ch/eitchnet/privilege/handler/DefaultPrivilegeHandler.java
index 9cc7e9127..a152e8cbd 100644
--- a/src/main/java/ch/eitchnet/privilege/handler/DefaultPrivilegeHandler.java
+++ b/src/main/java/ch/eitchnet/privilege/handler/DefaultPrivilegeHandler.java
@@ -31,9 +31,9 @@ import java.util.Set;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
+import ch.eitchnet.privilege.base.AccessDeniedException;
+import ch.eitchnet.privilege.base.PrivilegeException;
 import ch.eitchnet.privilege.helper.ClassHelper;
-import ch.eitchnet.privilege.i18n.AccessDeniedException;
-import ch.eitchnet.privilege.i18n.PrivilegeException;
 import ch.eitchnet.privilege.model.Certificate;
 import ch.eitchnet.privilege.model.PrivilegeRep;
 import ch.eitchnet.privilege.model.Restrictable;
@@ -718,7 +718,8 @@ public class DefaultPrivilegeHandler implements PrivilegeHandler {
 			DefaultPrivilegeHandler.logger.info("User " + username + " authenticated: " + session);
 
 		} catch (RuntimeException e) {
-			DefaultPrivilegeHandler.logger.error("User " + username + " Failed to authenticate: " + e.getLocalizedMessage());
+			DefaultPrivilegeHandler.logger.error("User " + username + " Failed to authenticate: "
+					+ e.getLocalizedMessage());
 			throw e;
 		} finally {
 			clearPassword(password);
@@ -786,7 +787,8 @@ public class DefaultPrivilegeHandler implements PrivilegeHandler {
 
 			Role role = this.persistenceHandler.getRole(roleName);
 			if (role == null) {
-				DefaultPrivilegeHandler.logger.error("No role is defined with name " + roleName + " which is configured for user " + user);
+				DefaultPrivilegeHandler.logger.error("No role is defined with name " + roleName
+						+ " which is configured for user " + user);
 				continue;
 			}
 
@@ -1188,7 +1190,8 @@ public class DefaultPrivilegeHandler implements PrivilegeHandler {
 		this.sessionMap.put(sessionId, new CertificateSessionPair(session, systemUserCertificate));
 
 		// log
-		DefaultPrivilegeHandler.logger.info("The system user " + systemUsername + " is logged in with session " + session);
+		DefaultPrivilegeHandler.logger.info("The system user " + systemUsername + " is logged in with session "
+				+ session);
 
 		return systemUserCertificate;
 	}
diff --git a/src/main/java/ch/eitchnet/privilege/handler/PersistenceHandler.java b/src/main/java/ch/eitchnet/privilege/handler/PersistenceHandler.java
index bba8f20c0..498f6e8e7 100644
--- a/src/main/java/ch/eitchnet/privilege/handler/PersistenceHandler.java
+++ b/src/main/java/ch/eitchnet/privilege/handler/PersistenceHandler.java
@@ -118,7 +118,7 @@ public interface PersistenceHandler {
 	/**
 	 * Informs this {@link PersistenceHandler} to persist any changes which need to be saved
 	 * 
-	 * @return true if changes were persisted successfully, false if something went wrong
+	 * @return true if changes were persisted successfully, false if nothing needed to be persisted
 	 */
 	public boolean persist();
 
diff --git a/src/main/java/ch/eitchnet/privilege/handler/PrivilegeHandler.java b/src/main/java/ch/eitchnet/privilege/handler/PrivilegeHandler.java
index 4f2c54b2a..7889905e7 100644
--- a/src/main/java/ch/eitchnet/privilege/handler/PrivilegeHandler.java
+++ b/src/main/java/ch/eitchnet/privilege/handler/PrivilegeHandler.java
@@ -22,8 +22,8 @@ package ch.eitchnet.privilege.handler;
 import java.util.List;
 import java.util.Locale;
 
-import ch.eitchnet.privilege.i18n.AccessDeniedException;
-import ch.eitchnet.privilege.i18n.PrivilegeException;
+import ch.eitchnet.privilege.base.AccessDeniedException;
+import ch.eitchnet.privilege.base.PrivilegeException;
 import ch.eitchnet.privilege.model.Certificate;
 import ch.eitchnet.privilege.model.PrivilegeRep;
 import ch.eitchnet.privilege.model.Restrictable;
@@ -401,7 +401,7 @@ public interface PrivilegeHandler {
 	 * </p>
 	 * 
 	 * <p>
-	 * If the user is not the administrator, then a {@link ch.eitchnet.privilege.i18n.PrivilegeException} is thrown
+	 * If the user is not the administrator, then a {@link ch.eitchnet.privilege.base.PrivilegeException} is thrown
 	 * </p>
 	 * 
 	 * @param certificate
diff --git a/src/main/java/ch/eitchnet/privilege/handler/XmlPersistenceHandler.java b/src/main/java/ch/eitchnet/privilege/handler/XmlPersistenceHandler.java
index 2d5fc12b8..6ea6fda2e 100644
--- a/src/main/java/ch/eitchnet/privilege/handler/XmlPersistenceHandler.java
+++ b/src/main/java/ch/eitchnet/privilege/handler/XmlPersistenceHandler.java
@@ -35,9 +35,9 @@ import org.dom4j.Element;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
+import ch.eitchnet.privilege.base.PrivilegeException;
 import ch.eitchnet.privilege.helper.XmlConstants;
 import ch.eitchnet.privilege.helper.XmlHelper;
-import ch.eitchnet.privilege.i18n.PrivilegeException;
 import ch.eitchnet.privilege.model.UserState;
 import ch.eitchnet.privilege.model.internal.Privilege;
 import ch.eitchnet.privilege.model.internal.Role;
@@ -150,11 +150,13 @@ public class XmlPersistenceHandler implements PersistenceHandler {
 			throw new PrivilegeException("[" + PersistenceHandler.class.getName() + "] Defined parameter "
 					+ XmlConstants.XML_PARAM_MODEL_FILE + " is invalid");
 		}
+
 		// get model file
 		File modelFile = new File(this.modelPath);
 		boolean modelFileUnchanged = modelFile.exists() && modelFile.lastModified() == this.modelsFileDate;
-		if (!(modelFileUnchanged && this.roleMapDirty && this.userMapDirty)) {
-			XmlPersistenceHandler.logger.warn("Not persisting as current file is unchanged and model data is not dirty");
+		if (modelFileUnchanged && !this.roleMapDirty && !this.userMapDirty) {
+			XmlPersistenceHandler.logger
+					.warn("Not persisting as current file is unchanged and model data is not dirty");
 			return false;
 		}
 
@@ -181,19 +183,14 @@ public class XmlPersistenceHandler implements PersistenceHandler {
 		}
 		rootElement.add(rolesElement);
 
-		// reset dirty states and return if something was dirty, false otherwise
-		if (this.userMapDirty || this.roleMapDirty) {
-			this.userMapDirty = false;
-			this.roleMapDirty = false;
-
-			return true;
-
-		}
+		// now write the file
+		XmlHelper.writeElement(rootElement, modelFile);
 
+		// reset dirty states
 		this.userMapDirty = false;
 		this.roleMapDirty = false;
 
-		return false;
+		return true;
 	}
 
 	/**
@@ -259,10 +256,13 @@ public class XmlPersistenceHandler implements PersistenceHandler {
 	 * @see ch.eitchnet.privilege.handler.PersistenceHandler#initialize(java.util.Map)
 	 */
 	@Override
-	public void initialize(Map<String, String> parameterMap) {
+	public void initialize(Map<String, String> paramsMap) {
+
+		// copy parameter map
+		this.parameterMap = Collections.unmodifiableMap(new HashMap<String, String>(paramsMap));
 
 		// get and validate base bath
-		String basePath = parameterMap.get(XmlConstants.XML_PARAM_BASE_PATH);
+		String basePath = this.parameterMap.get(XmlConstants.XML_PARAM_BASE_PATH);
 		File basePathF = new File(basePath);
 		if (!basePathF.exists() && !basePathF.isDirectory()) {
 			throw new PrivilegeException("[" + PersistenceHandler.class.getName() + "] Defined parameter "
@@ -270,7 +270,7 @@ public class XmlPersistenceHandler implements PersistenceHandler {
 		}
 
 		// get model file name
-		String modelFileName = parameterMap.get(XmlConstants.XML_PARAM_MODEL_FILE);
+		String modelFileName = this.parameterMap.get(XmlConstants.XML_PARAM_MODEL_FILE);
 		if (modelFileName == null || modelFileName.isEmpty()) {
 			throw new PrivilegeException("[" + PersistenceHandler.class.getName() + "] Defined parameter "
 					+ XmlConstants.XML_PARAM_MODEL_FILE + " is invalid");
@@ -321,9 +321,11 @@ public class XmlPersistenceHandler implements PersistenceHandler {
 			for (Element roleElement : rolesElementList) {
 				String roleName = roleElement.getTextTrim();
 				if (roleName.isEmpty()) {
-					XmlPersistenceHandler.logger.error("User " + username + " has a role defined with no name, Skipped.");
+					XmlPersistenceHandler.logger.error("User " + username
+							+ " has a role defined with no name, Skipped.");
 				} else if (!this.roleMap.containsKey(roleName)) {
-					XmlPersistenceHandler.logger.error("User " + username + " has a inexistant role " + roleName + ", Skipped.");
+					XmlPersistenceHandler.logger.error("User " + username + " has a inexistant role " + roleName
+							+ ", Skipped.");
 				} else {
 					roles.add(roleName);
 				}
diff --git a/src/main/java/ch/eitchnet/privilege/helper/ClassHelper.java b/src/main/java/ch/eitchnet/privilege/helper/ClassHelper.java
index 41b10b775..5852805d8 100644
--- a/src/main/java/ch/eitchnet/privilege/helper/ClassHelper.java
+++ b/src/main/java/ch/eitchnet/privilege/helper/ClassHelper.java
@@ -19,7 +19,7 @@
  */
 package ch.eitchnet.privilege.helper;
 
-import ch.eitchnet.privilege.i18n.PrivilegeException;
+import ch.eitchnet.privilege.base.PrivilegeException;
 
 /**
  * The {@link ClassHelper} class is a helper to instantiate classes using reflection
diff --git a/src/main/java/ch/eitchnet/privilege/helper/InitializationHelper.java b/src/main/java/ch/eitchnet/privilege/helper/InitializationHelper.java
index 94ff3d9d2..401cdb5fd 100644
--- a/src/main/java/ch/eitchnet/privilege/helper/InitializationHelper.java
+++ b/src/main/java/ch/eitchnet/privilege/helper/InitializationHelper.java
@@ -29,11 +29,11 @@ import org.dom4j.Element;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
+import ch.eitchnet.privilege.base.PrivilegeException;
 import ch.eitchnet.privilege.handler.DefaultPrivilegeHandler;
 import ch.eitchnet.privilege.handler.EncryptionHandler;
 import ch.eitchnet.privilege.handler.PersistenceHandler;
 import ch.eitchnet.privilege.handler.PrivilegeHandler;
-import ch.eitchnet.privilege.i18n.PrivilegeException;
 import ch.eitchnet.privilege.policy.PrivilegePolicy;
 import ch.eitchnet.utils.helper.StringHelper;
 
diff --git a/src/main/java/ch/eitchnet/privilege/helper/XmlHelper.java b/src/main/java/ch/eitchnet/privilege/helper/XmlHelper.java
index eec3c9eb2..900c8ca87 100644
--- a/src/main/java/ch/eitchnet/privilege/helper/XmlHelper.java
+++ b/src/main/java/ch/eitchnet/privilege/helper/XmlHelper.java
@@ -37,7 +37,7 @@ import org.dom4j.io.XMLWriter;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
-import ch.eitchnet.privilege.i18n.PrivilegeException;
+import ch.eitchnet.privilege.base.PrivilegeException;
 
 /**
  * Helper class for performing XML based tasks using Dom4J
diff --git a/src/main/java/ch/eitchnet/privilege/model/Certificate.java b/src/main/java/ch/eitchnet/privilege/model/Certificate.java
index 87d30a3da..0d165e57c 100644
--- a/src/main/java/ch/eitchnet/privilege/model/Certificate.java
+++ b/src/main/java/ch/eitchnet/privilege/model/Certificate.java
@@ -23,8 +23,8 @@ import java.io.Serializable;
 import java.util.Locale;
 import java.util.Map;
 
+import ch.eitchnet.privilege.base.PrivilegeException;
 import ch.eitchnet.privilege.handler.PrivilegeHandler;
-import ch.eitchnet.privilege.i18n.PrivilegeException;
 import ch.eitchnet.privilege.model.internal.Session;
 
 /**
diff --git a/src/main/java/ch/eitchnet/privilege/model/PrivilegeRep.java b/src/main/java/ch/eitchnet/privilege/model/PrivilegeRep.java
index e13d6a1f4..ca3b596d9 100644
--- a/src/main/java/ch/eitchnet/privilege/model/PrivilegeRep.java
+++ b/src/main/java/ch/eitchnet/privilege/model/PrivilegeRep.java
@@ -22,8 +22,8 @@ package ch.eitchnet.privilege.model;
 import java.io.Serializable;
 import java.util.Set;
 
+import ch.eitchnet.privilege.base.PrivilegeException;
 import ch.eitchnet.privilege.handler.PrivilegeHandler;
-import ch.eitchnet.privilege.i18n.PrivilegeException;
 import ch.eitchnet.privilege.model.internal.Privilege;
 import ch.eitchnet.privilege.model.internal.Role;
 import ch.eitchnet.privilege.policy.PrivilegePolicy;
diff --git a/src/main/java/ch/eitchnet/privilege/model/internal/Privilege.java b/src/main/java/ch/eitchnet/privilege/model/internal/Privilege.java
index c62456fbd..55c4fe1a5 100644
--- a/src/main/java/ch/eitchnet/privilege/model/internal/Privilege.java
+++ b/src/main/java/ch/eitchnet/privilege/model/internal/Privilege.java
@@ -23,8 +23,8 @@ import java.util.Collections;
 import java.util.HashSet;
 import java.util.Set;
 
+import ch.eitchnet.privilege.base.PrivilegeException;
 import ch.eitchnet.privilege.handler.PrivilegeHandler;
-import ch.eitchnet.privilege.i18n.PrivilegeException;
 import ch.eitchnet.privilege.model.PrivilegeRep;
 import ch.eitchnet.privilege.model.Restrictable;
 import ch.eitchnet.privilege.policy.PrivilegePolicy;
diff --git a/src/main/java/ch/eitchnet/privilege/model/internal/Role.java b/src/main/java/ch/eitchnet/privilege/model/internal/Role.java
index ab929ffde..d6825717b 100644
--- a/src/main/java/ch/eitchnet/privilege/model/internal/Role.java
+++ b/src/main/java/ch/eitchnet/privilege/model/internal/Role.java
@@ -23,7 +23,7 @@ import java.util.Collections;
 import java.util.HashMap;
 import java.util.Map;
 
-import ch.eitchnet.privilege.i18n.PrivilegeException;
+import ch.eitchnet.privilege.base.PrivilegeException;
 import ch.eitchnet.privilege.model.PrivilegeRep;
 import ch.eitchnet.privilege.model.RoleRep;
 
diff --git a/src/main/java/ch/eitchnet/privilege/model/internal/Session.java b/src/main/java/ch/eitchnet/privilege/model/internal/Session.java
index 7e3bb8614..4abcd08d5 100644
--- a/src/main/java/ch/eitchnet/privilege/model/internal/Session.java
+++ b/src/main/java/ch/eitchnet/privilege/model/internal/Session.java
@@ -19,8 +19,8 @@
  */
 package ch.eitchnet.privilege.model.internal;
 
+import ch.eitchnet.privilege.base.PrivilegeException;
 import ch.eitchnet.privilege.handler.PrivilegeHandler;
-import ch.eitchnet.privilege.i18n.PrivilegeException;
 import ch.eitchnet.privilege.model.Certificate;
 
 /**
diff --git a/src/main/java/ch/eitchnet/privilege/model/internal/User.java b/src/main/java/ch/eitchnet/privilege/model/internal/User.java
index 9e12026ac..0405ecec3 100644
--- a/src/main/java/ch/eitchnet/privilege/model/internal/User.java
+++ b/src/main/java/ch/eitchnet/privilege/model/internal/User.java
@@ -26,7 +26,7 @@ import java.util.Locale;
 import java.util.Map;
 import java.util.Set;
 
-import ch.eitchnet.privilege.i18n.PrivilegeException;
+import ch.eitchnet.privilege.base.PrivilegeException;
 import ch.eitchnet.privilege.model.UserRep;
 import ch.eitchnet.privilege.model.UserState;
 
@@ -91,9 +91,6 @@ public final class User {
 		if (username == null || username.isEmpty()) {
 			throw new PrivilegeException("No username defined!");
 		}
-
-		// password may be null, meaning not able to login
-
 		if (firstname == null || firstname.isEmpty()) {
 			throw new PrivilegeException("No firstname defined!");
 		}
@@ -104,9 +101,10 @@ public final class User {
 			throw new PrivilegeException("No userState defined!");
 		}
 
+		// password may be null, meaning not able to login
 		// roles may be null, meaning not able to login and must be added later
-
-		// local may be null, meaning use system default
+		// locale may be null, meaning use system default
+		// properties may be null, meaning no properties
 
 		this.userId = userId;
 
@@ -117,11 +115,20 @@ public final class User {
 		this.firstname = firstname;
 		this.surname = surname;
 
-		this.roles = Collections.unmodifiableSet(roles);
+		if (roles == null)
+			this.roles = Collections.emptySet();
+		else
+			this.roles = Collections.unmodifiableSet(roles);
 
-		this.locale = locale;
+		if (locale == null)
+			this.locale = Locale.getDefault();
+		else
+			this.locale = locale;
 
-		this.propertyMap = Collections.unmodifiableMap(propertyMap);
+		if (propertyMap == null)
+			this.propertyMap = Collections.emptyMap();
+		else
+			this.propertyMap = Collections.unmodifiableMap(propertyMap);
 	}
 
 	/**
diff --git a/src/main/java/ch/eitchnet/privilege/policy/DefaultPrivilege.java b/src/main/java/ch/eitchnet/privilege/policy/DefaultPrivilege.java
index ebb061656..3db6be69b 100644
--- a/src/main/java/ch/eitchnet/privilege/policy/DefaultPrivilege.java
+++ b/src/main/java/ch/eitchnet/privilege/policy/DefaultPrivilege.java
@@ -19,8 +19,8 @@
  */
 package ch.eitchnet.privilege.policy;
 
-import ch.eitchnet.privilege.i18n.AccessDeniedException;
-import ch.eitchnet.privilege.i18n.PrivilegeException;
+import ch.eitchnet.privilege.base.AccessDeniedException;
+import ch.eitchnet.privilege.base.PrivilegeException;
 import ch.eitchnet.privilege.model.Restrictable;
 import ch.eitchnet.privilege.model.internal.Privilege;
 import ch.eitchnet.privilege.model.internal.Role;
diff --git a/src/main/java/ch/eitchnet/privilege/policy/PrivilegePolicy.java b/src/main/java/ch/eitchnet/privilege/policy/PrivilegePolicy.java
index 50fc79837..62041e636 100644
--- a/src/main/java/ch/eitchnet/privilege/policy/PrivilegePolicy.java
+++ b/src/main/java/ch/eitchnet/privilege/policy/PrivilegePolicy.java
@@ -19,7 +19,7 @@
  */
 package ch.eitchnet.privilege.policy;
 
-import ch.eitchnet.privilege.i18n.AccessDeniedException;
+import ch.eitchnet.privilege.base.AccessDeniedException;
 import ch.eitchnet.privilege.model.Restrictable;
 import ch.eitchnet.privilege.model.internal.Privilege;
 import ch.eitchnet.privilege.model.internal.Role;