diff -r cc60c8dd7924 -r 5bc2bb8b7946 relpipe-data/principles.xml
--- a/relpipe-data/principles.xml	Fri Nov 26 22:14:18 2021 +0100
+++ b/relpipe-data/principles.xml	Mon Feb 21 00:43:11 2022 +0100
@@ -103,7 +103,7 @@
 			-->
 		</p>
 		
-		<h2>Optional complexity</h2>
+		<h2 id="optional_complexity">Optional complexity</h2>
 		
 		<p>
 			We are not scared by things like XML, SQL, RDF, Java or even C++ and we do not hate them.