--- dds-xtypes-v13_typeobject-20190301.idl	2025-08-14 06:59:53
+++ dds-xtypes-rtf4_typeobject-issue-36.idl	2025-08-14 08:25:35
@@ -44,7 +44,8 @@
     const octet TK_STRUCTURE  = 0x51;
     const octet TK_UNION      = 0x52;
     const octet TK_BITSET     = 0x53;
-      
+    const octet TK_UNION64    = 0x54;
+
     // Collection TKs
     const octet TK_SEQUENCE   = 0x60;
     const octet TK_ARRAY      = 0x61;
@@ -455,7 +456,7 @@
         CommonStructMember                         common;
         MinimalMemberDetail                        detail;
     };
-    // Ordered by common.member_id
+    // Ordered by the member_index
     typedef sequence<MinimalStructMember> MinimalStructMemberSeq;
 
     
@@ -507,6 +508,7 @@
     // Case labels that apply to a member of a union type
     // Ordered by their values
     typedef sequence<long> UnionCaseLabelSeq;
+    typedef sequence<long long> Union64CaseLabelSeq;
 
     @extensibility(FINAL) @nested
     struct CommonUnionMember {
@@ -514,6 +516,14 @@
         UnionMemberFlag             member_flags;
         TypeIdentifier              type_id;
         UnionCaseLabelSeq           label_seq;
+    };
+    
+    @extensibility(FINAL) @nested
+    struct CommonUnion64Member {
+        MemberId                    member_id;
+        UnionMemberFlag             member_flags;
+        TypeIdentifier              type_id;
+        Union64CaseLabelSeq         label_seq;
     };
 
     // Member of a union type
@@ -525,6 +535,15 @@
     // Ordered by member_index
     typedef sequence<CompleteUnionMember> CompleteUnionMemberSeq;
 
+    // Member of a union type (64-bit discriminator version)
+    @extensibility(APPENDABLE) @nested
+    struct CompleteUnion64Member {
+        CommonUnion64Member      common;
+        CompleteMemberDetail     detail;
+    };
+    // Ordered by member_index
+    typedef sequence<CompleteUnion64Member> CompleteUnion64MemberSeq;
+
     // Member of a union type
     @extensibility(APPENDABLE) @nested
     struct MinimalUnionMember {
@@ -533,6 +552,15 @@
     };
     // Ordered by MinimalUnionMember.common.member_id
     typedef sequence<MinimalUnionMember> MinimalUnionMemberSeq;
+    
+    // Member of a union type (64-bit discriminator version)
+    @extensibility(APPENDABLE) @nested
+    struct MinimalUnion64Member {
+        CommonUnion64Member   common;
+        MinimalMemberDetail   detail;
+    };
+    // Ordered by MinimalUnion64Member.common.member_id
+    typedef sequence<MinimalUnion64Member> MinimalUnion64MemberSeq;
 
     @extensibility(FINAL) @nested
     struct CommonDiscriminatorMember {
@@ -570,6 +598,12 @@
         CompleteUnionHeader          header;
         CompleteDiscriminatorMember  discriminator;
         CompleteUnionMemberSeq       member_seq;
+    };
+    struct CompleteUnion64Type {
+        UnionTypeFlag                union_flags;
+        CompleteUnionHeader          header;
+        CompleteDiscriminatorMember  discriminator;
+        CompleteUnion64MemberSeq     member_seq;
     };
 
     @extensibility(FINAL) @nested
@@ -579,6 +613,13 @@
         MinimalDiscriminatorMember   discriminator;
         MinimalUnionMemberSeq        member_seq;
     };
+    @extensibility(FINAL) @nested
+    struct MinimalUnion64Type {
+        UnionTypeFlag                union_flags;
+        MinimalUnionHeader           header;
+        MinimalDiscriminatorMember   discriminator;
+        MinimalUnion64MemberSeq      member_seq;
+    };
 
     // --- Annotation: ----------------------------------------------------
     @extensibility(FINAL) @nested
@@ -954,6 +995,8 @@
             CompleteStructType     struct_type;
         case TK_UNION:
             CompleteUnionType      union_type;
+        case TK_UNION64:
+            CompleteUnion64Type    union64_type;
         case TK_BITSET:
             CompleteBitsetType     bitset_type;
         case TK_SEQUENCE:
@@ -988,6 +1031,8 @@
             MinimalStructType      struct_type;
         case TK_UNION:
             MinimalUnionType       union_type;
+        case TK_UNION64:
+            MinimalUnion64Type     union64_type;
         case TK_BITSET:
             MinimalBitsetType      bitset_type;
         case TK_SEQUENCE: