diff --git a/resources/schema/structures.xsd b/resources/schema/structures.xsd
index fc7a567..1112e11 100644
--- a/resources/schema/structures.xsd
+++ b/resources/schema/structures.xsd
@@ -326,13 +326,16 @@
               </xsd:element>
             </xsd:sequence>
             <xsd:attribute name="id" type="xsd:integer"/>
+            <xsd:attribute name="parent_id" type="xsd:integer"/>
             <xsd:attribute name="tempId" type="xsd:integer"/>
-            <xsd:attribute name="label" use="required" type="xsd:string"/>
+            <xsd:attribute name="label" type="xsd:string"/>
+            <xsd:attribute name="formal_descendants" type="xsd:string"/>
             <xsd:attribute name="type" use="required">
               <xsd:simpleType>
                 <xsd:restriction base="xsd:string">
                   <xsd:enumeration value="single"/>
                   <xsd:enumeration value="collocation"/>
+                  <xsd:enumeration value="formal"/>
                   <xsd:enumeration value="other"/>
                 </xsd:restriction>
               </xsd:simpleType>