diff --git a/resources/schema/inventory.xsd b/resources/schema/inventory.xsd
index b50968d..b63ac78 100644
--- a/resources/schema/inventory.xsd
+++ b/resources/schema/inventory.xsd
@@ -93,7 +93,9 @@
         <xsd:element name="component" type="componentType" minOccurs="2" maxOccurs="unbounded"/>
       </xsd:choice>
     </xsd:sequence>
-    <xsd:attribute name="id" type="xsd:int" use="required"/> 
+    <xsd:attribute name="id" type="xsd:int"/>
+    <xsd:attribute name="sloleks_id" type="xsd:string"/>
+    <xsd:attribute name="sloleks_key" type="xsd:string"/>
     <xsd:attribute name="type" use="required"> <!-- types of headwords allowed; hmm, probably should standardise allowed settings -->
       <xsd:simpleType>
         <xsd:restriction base="xsd:string">
@@ -256,6 +258,7 @@
         <xsd:attribute name="sloleks" type="xsd:string"/> <!-- Sloleks ID -->
         <xsd:attribute name="kol" type="xsd:string"/> <!-- legacy attribute for the word's lemma -->
         <xsd:attribute name="lexical_unit_lexeme_id" type="xsd:int"/> <!-- ID within its lexical unit -->
+        <xsd:attribute name="lexeme_id" type="xsd:int"/> <!-- ID of the component's lexeme -->
       </xsd:extension>
     </xsd:simpleContent>
   </xsd:complexType>