diff --git a/.classpath b/.classpath
index ace8266..2d7c6a5 100644
--- a/.classpath
+++ b/.classpath
@@ -15,16 +15,19 @@
 		<attributes>
 			<attribute name="optional" value="true"/>
 			<attribute name="maven.pomderived" value="true"/>
+			<attribute name="test" value="true"/>
 		</attributes>
 	</classpathentry>
 	<classpathentry excluding="**" kind="src" output="target/test-classes" path="src/test/resources">
 		<attributes>
 			<attribute name="maven.pomderived" value="true"/>
+			<attribute name="test" value="true"/>
 		</attributes>
 	</classpathentry>
 	<classpathentry kind="con" path="org.eclipse.m2e.MAVEN2_CLASSPATH_CONTAINER">
 		<attributes>
 			<attribute name="maven.pomderived" value="true"/>
+			<attribute name="org.eclipse.jst.component.nondependency" value=""/>
 		</attributes>
 	</classpathentry>
 	<classpathentry kind="con" path="org.eclipse.jdt.launching.JRE_CONTAINER/org.eclipse.jdt.internal.debug.ui.launcher.StandardVMType/JavaSE-1.8">
diff --git a/.project b/.project
index a9b54dd..805ba88 100644
--- a/.project
+++ b/.project
@@ -5,11 +5,21 @@
 	<projects>
 	</projects>
 	<buildSpec>
+		<buildCommand>
+			<name>org.eclipse.wst.common.project.facet.core.builder</name>
+			<arguments>
+			</arguments>
+		</buildCommand>
 		<buildCommand>
 			<name>org.eclipse.jdt.core.javabuilder</name>
 			<arguments>
 			</arguments>
 		</buildCommand>
+		<buildCommand>
+			<name>org.eclipse.wst.validation.validationbuilder</name>
+			<arguments>
+			</arguments>
+		</buildCommand>
 		<buildCommand>
 			<name>org.eclipse.m2e.core.maven2Builder</name>
 			<arguments>
@@ -17,7 +27,10 @@
 		</buildCommand>
 	</buildSpec>
 	<natures>
+		<nature>org.eclipse.jem.workbench.JavaEMFNature</nature>
+		<nature>org.eclipse.wst.common.modulecore.ModuleCoreNature</nature>
 		<nature>org.eclipse.jdt.core.javanature</nature>
 		<nature>org.eclipse.m2e.core.maven2Nature</nature>
+		<nature>org.eclipse.wst.common.project.facet.core.nature</nature>
 	</natures>
 </projectDescription>
diff --git a/.settings/org.eclipse.jdt.core.prefs b/.settings/org.eclipse.jdt.core.prefs
index 672496e..8445b6b 100644
--- a/.settings/org.eclipse.jdt.core.prefs
+++ b/.settings/org.eclipse.jdt.core.prefs
@@ -9,4 +9,5 @@ org.eclipse.jdt.core.compiler.debug.sourceFile=generate
 org.eclipse.jdt.core.compiler.problem.assertIdentifier=error
 org.eclipse.jdt.core.compiler.problem.enumIdentifier=error
 org.eclipse.jdt.core.compiler.problem.forbiddenReference=warning
+org.eclipse.jdt.core.compiler.release=disabled
 org.eclipse.jdt.core.compiler.source=1.8
diff --git a/.settings/org.eclipse.wst.common.component b/.settings/org.eclipse.wst.common.component
new file mode 100644
index 0000000..f9cfd7b
--- /dev/null
+++ b/.settings/org.eclipse.wst.common.component
@@ -0,0 +1,6 @@
+<?xml version="1.0" encoding="UTF-8"?><project-modules id="moduleCoreId" project-version="1.5.0">
+    <wb-module deploy-name="storagehub-model_TRUNK">
+        <wb-resource deploy-path="/" source-path="/src/main/java"/>
+        <wb-resource deploy-path="/" source-path="/src/main/resources"/>
+    </wb-module>
+</project-modules>
diff --git a/.settings/org.eclipse.wst.common.project.facet.core.xml b/.settings/org.eclipse.wst.common.project.facet.core.xml
new file mode 100644
index 0000000..fb95c45
--- /dev/null
+++ b/.settings/org.eclipse.wst.common.project.facet.core.xml
@@ -0,0 +1,5 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<faceted-project>
+  <installed facet="java" version="1.8"/>
+  <installed facet="jst.utility" version="1.0"/>
+</faceted-project>
diff --git a/.settings/org.eclipse.wst.validation.prefs b/.settings/org.eclipse.wst.validation.prefs
new file mode 100644
index 0000000..04cad8c
--- /dev/null
+++ b/.settings/org.eclipse.wst.validation.prefs
@@ -0,0 +1,2 @@
+disabled=06target
+eclipse.preferences.version=1
diff --git a/src/main/java/org/gcube/common/storagehub/model/exceptions/BackendGenericError.java b/src/main/java/org/gcube/common/storagehub/model/exceptions/BackendGenericError.java
index a7d6360..35f4a32 100644
--- a/src/main/java/org/gcube/common/storagehub/model/exceptions/BackendGenericError.java
+++ b/src/main/java/org/gcube/common/storagehub/model/exceptions/BackendGenericError.java
@@ -26,5 +26,15 @@ public class BackendGenericError extends StorageHubException{
 		super(cause);
 		// TODO Auto-generated constructor stub
 	}
+
+	@Override
+	public String getErrorMessage() {
+		return "generic error in the backend";
+	}
+
+	@Override
+	public int getStatus() {
+		return 500;
+	}
 	
 }
diff --git a/src/main/java/org/gcube/common/storagehub/model/exceptions/IdNotFoundException.java b/src/main/java/org/gcube/common/storagehub/model/exceptions/IdNotFoundException.java
index 3147c23..56322de 100644
--- a/src/main/java/org/gcube/common/storagehub/model/exceptions/IdNotFoundException.java
+++ b/src/main/java/org/gcube/common/storagehub/model/exceptions/IdNotFoundException.java
@@ -17,6 +17,14 @@ public class IdNotFoundException extends StorageHubException {
 		// TODO Auto-generated constructor stub
 	}
 
-	
+	@Override
+	public String getErrorMessage() {
+		return "item not found";
+	}
+
+	@Override
+	public int getStatus() {
+		return 404;
+	}
 	
 }
diff --git a/src/main/java/org/gcube/common/storagehub/model/exceptions/InvalidCallParameters.java b/src/main/java/org/gcube/common/storagehub/model/exceptions/InvalidCallParameters.java
index 92194a4..d0fc43b 100644
--- a/src/main/java/org/gcube/common/storagehub/model/exceptions/InvalidCallParameters.java
+++ b/src/main/java/org/gcube/common/storagehub/model/exceptions/InvalidCallParameters.java
@@ -27,4 +27,14 @@ public class InvalidCallParameters extends StorageHubException {
 		// TODO Auto-generated constructor stub
 	}
 
+	@Override
+	public String getErrorMessage() {
+		return "invalid call parameter";
+	}
+
+	@Override
+	public int getStatus() {
+		return 400;
+	}
+	
 }
diff --git a/src/main/java/org/gcube/common/storagehub/model/exceptions/InvalidItemException.java b/src/main/java/org/gcube/common/storagehub/model/exceptions/InvalidItemException.java
index 4a25ea7..0bd4d7b 100644
--- a/src/main/java/org/gcube/common/storagehub/model/exceptions/InvalidItemException.java
+++ b/src/main/java/org/gcube/common/storagehub/model/exceptions/InvalidItemException.java
@@ -27,6 +27,14 @@ public class InvalidItemException extends StorageHubException {
 		// TODO Auto-generated constructor stub
 	}
 	
-	
+	@Override
+	public String getErrorMessage() {
+		return "invalid item in request";
+	}
+
+	@Override
+	public int getStatus() {
+		return 500;
+	}
 
 }
diff --git a/src/main/java/org/gcube/common/storagehub/model/exceptions/ItemAlreadyExistsException.java b/src/main/java/org/gcube/common/storagehub/model/exceptions/ItemAlreadyExistsException.java
index 7492d4e..18fa388 100644
--- a/src/main/java/org/gcube/common/storagehub/model/exceptions/ItemAlreadyExistsException.java
+++ b/src/main/java/org/gcube/common/storagehub/model/exceptions/ItemAlreadyExistsException.java
@@ -27,4 +27,13 @@ public class ItemAlreadyExistsException extends StorageHubException {
 		// TODO Auto-generated constructor stub
 	}
 	
+	@Override
+	public String getErrorMessage() {
+		return "item already exists";
+	}
+
+	@Override
+	public int getStatus() {
+		return 400;
+	}
 }
diff --git a/src/main/java/org/gcube/common/storagehub/model/exceptions/ItemLockedException.java b/src/main/java/org/gcube/common/storagehub/model/exceptions/ItemLockedException.java
new file mode 100644
index 0000000..e5865be
--- /dev/null
+++ b/src/main/java/org/gcube/common/storagehub/model/exceptions/ItemLockedException.java
@@ -0,0 +1,40 @@
+package org.gcube.common.storagehub.model.exceptions;
+
+public class ItemLockedException extends StorageHubException {
+
+	/**
+	 * 
+	 */
+	private static final long serialVersionUID = 1L;
+
+	public ItemLockedException() {
+		super();
+		// TODO Auto-generated constructor stub
+	}
+
+	public ItemLockedException(String message, Throwable cause) {
+		super(message, cause);
+		// TODO Auto-generated constructor stub
+	}
+
+	public ItemLockedException(String message) {
+		super(message);
+		// TODO Auto-generated constructor stub
+	}
+
+	public ItemLockedException(Throwable cause) {
+		super(cause);
+		// TODO Auto-generated constructor stub
+	}
+
+	@Override
+	public String getErrorMessage() {
+		return "item locked";
+	}
+
+	@Override
+	public int getStatus() {
+		return 409;
+	}
+
+}
diff --git a/src/main/java/org/gcube/common/storagehub/model/exceptions/StorageHubException.java b/src/main/java/org/gcube/common/storagehub/model/exceptions/StorageHubException.java
index b1b7117..6b3764b 100644
--- a/src/main/java/org/gcube/common/storagehub/model/exceptions/StorageHubException.java
+++ b/src/main/java/org/gcube/common/storagehub/model/exceptions/StorageHubException.java
@@ -12,6 +12,10 @@ public abstract class StorageHubException extends Exception {
 		// TODO Auto-generated constructor stub
 	}
 
+	public abstract String getErrorMessage();
+	
+	public abstract int getStatus();
+	
 	public StorageHubException(String message, Throwable cause) {
 		super(message, cause);
 		// TODO Auto-generated constructor stub
diff --git a/src/main/java/org/gcube/common/storagehub/model/exceptions/UserNotAuthorizedException.java b/src/main/java/org/gcube/common/storagehub/model/exceptions/UserNotAuthorizedException.java
index b4ca6f3..9961c59 100644
--- a/src/main/java/org/gcube/common/storagehub/model/exceptions/UserNotAuthorizedException.java
+++ b/src/main/java/org/gcube/common/storagehub/model/exceptions/UserNotAuthorizedException.java
@@ -27,5 +27,14 @@ public class UserNotAuthorizedException extends StorageHubException {
 		// TODO Auto-generated constructor stub
 	}
 
+	@Override
+	public String getErrorMessage() {
+		return "user not authorized";
+	}
+
+	@Override
+	public int getStatus() {
+		return 401;
+	}
 	
 }