diff --git a/src/yang/etsi-nfv-common.yang b/src/yang/etsi-nfv-common.yang
index 3fb5a156783055c63aaf138e2028ddaa4121eca8..841e03ba940eca8e8acd99a4723b81c9c3b4a4bd 100644
--- a/src/yang/etsi-nfv-common.yang
+++ b/src/yang/etsi-nfv-common.yang
@@ -393,6 +393,19 @@ submodule etsi-nfv-common {
     }
   }
 
+  typedef external-lifecycle-management-script-event {
+    type enumeration {
+      enum "instantiation";
+      enum "scaling";
+      enum "healing";
+      enum "termination";
+      enum "vnf-flavour-change";
+      enum "vnf-operation-change";
+      enum "vnf-ext-conn-change";
+      enum "vnfinfo-modification";
+    }
+  }
+
   grouping local-affinity-or-anti-affinity-rule {
     list local-affinity-or-anti-affinity-rule {
       key "type scope";
diff --git a/src/yang/etsi-nfv-vnf.yang b/src/yang/etsi-nfv-vnf.yang
index bd8c032c652ee883d92b6aa251c002ed6b426dae..26cb57496417638ece2668566b7df73a481d9861 100755
--- a/src/yang/etsi-nfv-vnf.yang
+++ b/src/yang/etsi-nfv-vnf.yang
@@ -2977,10 +2977,25 @@ submodule etsi-nfv-vnf {
       }
 
       leaf-list event {
-        type internal-lifecycle-management-script-event;
+        type union {
+          type internal-lifecycle-management-script-event;
+          type external-lifecycle-management-script-event;
+        }
         description
           "Describes VNF lifecycle event(s) or an external stimulus
-           detected on a VNFM reference point.";
+           detected on a VNFM reference point.
+
+           If the event is of type 
+           internal-lifecycle-management-script-event, then depending
+           on whether the event is of type start-* or end-*, the
+           script associated with the VNF LCM operation needs to be 
+           executed before the event, or after the event,
+           respectively.
+
+           On the other hand, if the event is of type
+           external-lifecycle-management-script-event, then the
+           script associated with the event needs to be executed
+           for the given VNF LCM operation.";
         reference
           "GS NFV IFA011: Section 7.1.13 LifeCycleManagementScript
            information element";