diff --git a/README.md b/README.md
index fe310d3..e917e84 100644
--- a/README.md
+++ b/README.md
@@ -8,6 +8,8 @@ Le convertisseur est [converter.py](./converter.py).
 $ python converter.py l-systems.csv
 ```
 
+<!-- Pour valider : xmllint --schema data.xsd fichier.xml 1>/dev/null -->
+
 ## Rapport
 
 <!-- TODO: Push le PDF uniquement quand il est finalisé. -->
diff --git a/converter.py b/converter.py
index 825dc11..0bc7d6b 100644
--- a/converter.py
+++ b/converter.py
@@ -49,7 +49,7 @@ class System:
                 break
 
     def __repr__(self):
-        return pformat(self.__dict__, compact=True, width=120, sort_dicts=False)
+        return pformat(object=self.__dict__, compact=True, width=120, sort_dicts=False)
 
     def to_xml(self) -> XMLElement:
         """Convert the current system into an XML element"""
@@ -126,8 +126,11 @@ if __name__ == "__main__":
     # Generate XML
     xml = lsystems_xml(lsystems)
 
+    # Add XML model declaration
+    xml_string = '<?xml-model href="data.xsd"?>\n' + element_stringifier(xml).decode()
+
     # Output XML
-    dom = xml_parser(element_stringifier(xml))
+    dom = xml_parser(xml_string)
     pretty_xml = dom.toprettyxml(encoding="UTF-8").decode()
     if args.output:
         with open(args.output, "w") as output_file:
diff --git a/data.xsd b/data.xsd
new file mode 100644
index 0000000..59e298a
--- /dev/null
+++ b/data.xsd
@@ -0,0 +1,7 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema">
+
+  <!-- Root -->
+  <xs:element name="lsystems"></xs:element>
+
+</xs:schema>