diff --git a/sources/PropertyTree/AbstractProperty.php b/sources/PropertyTree/AbstractProperty.php
new file mode 100644
index 000000000..f91b8f87f
--- /dev/null
+++ b/sources/PropertyTree/AbstractProperty.php
@@ -0,0 +1,26 @@
+<?php
+
+/*
+ * @copyright   Copyright (C) 2010-2025 Combodo SAS
+ * @license     http://opensource.org/licenses/AGPL-3.0
+ */
+
+namespace Combodo\iTop\PropertyTree;
+
+use Combodo\iTop\PropertyTree\ValueType\AbstractValueType;
+
+abstract class AbstractProperty
+{
+	private ?AbstractValueType $oValueType;
+
+	public function GetValueType(): ?AbstractValueType
+	{
+		return $this->oValueType;
+	}
+
+	public function SetValueType(AbstractValueType $oValueType): void
+	{
+		$this->oValueType = $oValueType;
+	}
+
+}
diff --git a/sources/PropertyTree/CollectionOfTrees.php b/sources/PropertyTree/CollectionOfTrees.php
index 290b8832a..6cb4c70c4 100644
--- a/sources/PropertyTree/CollectionOfTrees.php
+++ b/sources/PropertyTree/CollectionOfTrees.php
@@ -7,6 +7,6 @@
 
 namespace Combodo\iTop\PropertyTree;
 
-class CollectionOfTrees
+class CollectionOfTrees extends AbstractProperty
 {
 }
diff --git a/sources/PropertyTree/CollectionOfValues.php b/sources/PropertyTree/CollectionOfValues.php
index 54d31cc76..e0c82dd5b 100644
--- a/sources/PropertyTree/CollectionOfValues.php
+++ b/sources/PropertyTree/CollectionOfValues.php
@@ -7,6 +7,6 @@
 
 namespace Combodo\iTop\PropertyTree;
 
-class CollectionOfValues
+class CollectionOfValues extends AbstractProperty
 {
 }
diff --git a/sources/PropertyTree/Property.php b/sources/PropertyTree/Property.php
index 333fe6543..0c7632784 100644
--- a/sources/PropertyTree/Property.php
+++ b/sources/PropertyTree/Property.php
@@ -7,6 +7,6 @@
 
 namespace Combodo\iTop\PropertyTree;
 
-class Property
+class Property extends AbstractProperty
 {
 }
diff --git a/sources/PropertyTree/PropertyTree.php b/sources/PropertyTree/PropertyTree.php
index 18a11582c..592e73eb2 100644
--- a/sources/PropertyTree/PropertyTree.php
+++ b/sources/PropertyTree/PropertyTree.php
@@ -7,6 +7,6 @@
 
 namespace Combodo\iTop\PropertyTree;
 
-class PropertyTree
+class PropertyTree extends AbstractProperty
 {
 }
diff --git a/sources/PropertyTree/ValueType/AbstractValueType.php b/sources/PropertyTree/ValueType/AbstractValueType.php
new file mode 100644
index 000000000..e91bfd52e
--- /dev/null
+++ b/sources/PropertyTree/ValueType/AbstractValueType.php
@@ -0,0 +1,12 @@
+<?php
+
+/*
+ * @copyright   Copyright (C) 2010-2025 Combodo SAS
+ * @license     http://opensource.org/licenses/AGPL-3.0
+ */
+
+namespace Combodo\iTop\PropertyTree\ValueType;
+
+abstract class AbstractValueType
+{
+}
diff --git a/sources/PropertyTree/ValueType/ValueTypeChoice.php b/sources/PropertyTree/ValueType/ValueTypeChoice.php
index 803ca4775..6b5e16ecd 100644
--- a/sources/PropertyTree/ValueType/ValueTypeChoice.php
+++ b/sources/PropertyTree/ValueType/ValueTypeChoice.php
@@ -7,6 +7,6 @@
 
 namespace Combodo\iTop\PropertyTree\ValueType;
 
-class ValueTypeChoice
+class ValueTypeChoice extends AbstractValueType
 {
 }
diff --git a/sources/PropertyTree/ValueType/ValueTypeClassAttribute.php b/sources/PropertyTree/ValueType/ValueTypeClassAttribute.php
index 18b02f11c..7f1f279cb 100644
--- a/sources/PropertyTree/ValueType/ValueTypeClassAttribute.php
+++ b/sources/PropertyTree/ValueType/ValueTypeClassAttribute.php
@@ -7,6 +7,6 @@
 
 namespace Combodo\iTop\PropertyTree\ValueType;
 
-class ValueTypeClassAttribute
+class ValueTypeClassAttribute extends AbstractValueType
 {
 }
diff --git a/sources/PropertyTree/ValueType/ValueTypeClassAttributeGroupBy.php b/sources/PropertyTree/ValueType/ValueTypeClassAttributeGroupBy.php
index 59e0dc470..a11d401b0 100644
--- a/sources/PropertyTree/ValueType/ValueTypeClassAttributeGroupBy.php
+++ b/sources/PropertyTree/ValueType/ValueTypeClassAttributeGroupBy.php
@@ -7,6 +7,6 @@
 
 namespace Combodo\iTop\PropertyTree\ValueType;
 
-class ValueTypeClassAttributeGroupBy
+class ValueTypeClassAttributeGroupBy extends AbstractValueType
 {
 }
diff --git a/sources/PropertyTree/ValueType/ValueTypeClassAttributeValue.php b/sources/PropertyTree/ValueType/ValueTypeClassAttributeValue.php
index 5404f4d35..33e524443 100644
--- a/sources/PropertyTree/ValueType/ValueTypeClassAttributeValue.php
+++ b/sources/PropertyTree/ValueType/ValueTypeClassAttributeValue.php
@@ -7,6 +7,6 @@
 
 namespace Combodo\iTop\PropertyTree\ValueType;
 
-class ValueTypeClassAttributeValue
+class ValueTypeClassAttributeValue extends AbstractValueType
 {
 }
diff --git a/sources/PropertyTree/ValueType/ValueTypeInteger.php b/sources/PropertyTree/ValueType/ValueTypeInteger.php
index a749a1290..c7c675ad8 100644
--- a/sources/PropertyTree/ValueType/ValueTypeInteger.php
+++ b/sources/PropertyTree/ValueType/ValueTypeInteger.php
@@ -7,6 +7,6 @@
 
 namespace Combodo\iTop\PropertyTree\ValueType;
 
-class ValueTypeInteger
+class ValueTypeInteger extends AbstractValueType
 {
 }
diff --git a/sources/PropertyTree/ValueType/ValueTypeLabel.php b/sources/PropertyTree/ValueType/ValueTypeLabel.php
index 23aba674e..05f63ef6f 100644
--- a/sources/PropertyTree/ValueType/ValueTypeLabel.php
+++ b/sources/PropertyTree/ValueType/ValueTypeLabel.php
@@ -7,6 +7,6 @@
 
 namespace Combodo\iTop\PropertyTree\ValueType;
 
-class ValueTypeLabel
+class ValueTypeLabel extends AbstractValueType
 {
 }
diff --git a/sources/PropertyTree/ValueType/ValueTypeOQL.php b/sources/PropertyTree/ValueType/ValueTypeOQL.php
index 3f640d2d9..7e04d27ef 100644
--- a/sources/PropertyTree/ValueType/ValueTypeOQL.php
+++ b/sources/PropertyTree/ValueType/ValueTypeOQL.php
@@ -7,6 +7,6 @@
 
 namespace Combodo\iTop\PropertyTree\ValueType;
 
-class ValueTypeOQL
+class ValueTypeOQL extends AbstractValueType
 {
 }
diff --git a/sources/PropertyTree/ValueType/ValueTypeProfileName.php b/sources/PropertyTree/ValueType/ValueTypeProfileName.php
index f00c45836..9c0bf3494 100644
--- a/sources/PropertyTree/ValueType/ValueTypeProfileName.php
+++ b/sources/PropertyTree/ValueType/ValueTypeProfileName.php
@@ -7,6 +7,6 @@
 
 namespace Combodo\iTop\PropertyTree\ValueType;
 
-class ValueTypeProfileName
+class ValueTypeProfileName extends AbstractValueType
 {
 }