diff --git a/03_TECHNICAL_CORE/ontology/ARCO_instances_sentinel.ttl b/03_TECHNICAL_CORE/ontology/ARCO_instances_sentinel.ttl
index 2425c50..efabf69 100644
--- a/03_TECHNICAL_CORE/ontology/ARCO_instances_sentinel.ttl
+++ b/03_TECHNICAL_CORE/ontology/ARCO_instances_sentinel.ttl
@@ -18,6 +18,7 @@
 
 :AnnexIII_List rdf:type :RegulatoryContent ;
   rdfs:label "Annex III List" ;
+  rdfs:comment "Mereological scaffold for modeled regulatory conditions. New Annex III categories add via bfo:0000051 (has_part). Peer regulation lists (e.g. GDPR_Article22_List) follow same pattern. Extension point by design — do not remove as orphaned." ;
   bfo:0000051 :AnnexIII_Condition_Q1 .  # has part
 
 :AnnexIII_Condition_Q1 rdf:type :RegulatoryContent ;