From 88d3c0d045a2ad36dff4b1f91fbda0157a951c5f Mon Sep 17 00:00:00 2001
From: Paul <PaulMartinsen@users.noreply.github.com>
Date: Tue, 24 Mar 2026 20:11:26 +1300
Subject: [PATCH 1/2] Fix epochs schema to resolve double nesting of
 `sdpi:Epoch` element.

---
 CHANGELOG.md                                  |  1 +
 .../timestamp/TimeStampVersion.xsd            | 19 ++++++++-----------
 2 files changed, 9 insertions(+), 11 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index db0033ef..cdf20407 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -26,6 +26,7 @@ Each section shall contain a list of action items of the following format: `<bri
 
 - Corrected three erroneous context-free codes in Table 3:8.3.2.10.2-1 ([#505](https://github.com/IHE/DEV.SDPi/issues/505))
 - Clarified referenced standards sections in 2:A and removed ISO prefix from IEEE/ISO standards for referential consistency ([#390](https://github.com/IHE/DEV.SDPi/issues/390))
+- Fixed TimeStampVersion.xsd to resolve double nesting of sdpi:Epoch element ([#520](https://github.com/IHE/DEV.SDPi/issues/520)). 
 
 ### Editorial Fixes
 
diff --git a/sources/extension-models/timestamp/TimeStampVersion.xsd b/sources/extension-models/timestamp/TimeStampVersion.xsd
index f96b410e..320976a4 100644
--- a/sources/extension-models/timestamp/TimeStampVersion.xsd
+++ b/sources/extension-models/timestamp/TimeStampVersion.xsd
@@ -48,7 +48,7 @@
   <!---->
   <!---->
   <!--Epochs-->
-  <xsd:element name="Epochs">
+  <xsd:element name="Epochs" type="sdpi:EpochsType">
     <xsd:annotation>
       <xsd:documentation>
         An extension to version epochs arising from non-slewing time adjustments.
@@ -56,16 +56,6 @@
         This extension can be attached to the pm:ClockState/ext:Extension element.
       </xsd:documentation>
     </xsd:annotation>
-    <xsd:complexType>
-      <xsd:sequence>
-        <xsd:element name="Epoch" type="sdpi:EpochsType" minOccurs="0" maxOccurs="unbounded" /> 
-      </xsd:sequence>
-      <xsd:attribute name="Version" type="sdpi:EpochVersion" use="required">
-        <xsd:annotation>
-          <xsd:documentation>Current epoch version. Implied value is 0.</xsd:documentation>
-        </xsd:annotation>
-      </xsd:attribute>
-    </xsd:complexType>
   </xsd:element>
   <xsd:complexType name="EpochsType">
     <xsd:annotation>
@@ -77,6 +67,13 @@
                    minOccurs="0"
                    maxOccurs="unbounded" />
     </xsd:sequence>
+    <xsd:attribute name="Version"
+                   type="sdpi:EpochVersion"
+                   use="required">
+      <xsd:annotation>
+        <xsd:documentation>Current epoch version. Implied value is 0.</xsd:documentation>
+      </xsd:annotation>
+    </xsd:attribute>
   </xsd:complexType>
   <xsd:complexType name="EpochType">
     <xsd:annotation>

From 1271e9e0acf1a8c4724d312d00617c741400cc7e Mon Sep 17 00:00:00 2001
From: Paul <PaulMartinsen@users.noreply.github.com>
Date: Thu, 2 Apr 2026 20:14:01 +1300
Subject: [PATCH 2/2] Changed version attribute to optional with a default
 value of 0, the first epoch before any abrupt adjustments are required.

---
 sources/extension-models/timestamp/TimeStampVersion.xsd | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/sources/extension-models/timestamp/TimeStampVersion.xsd b/sources/extension-models/timestamp/TimeStampVersion.xsd
index 320976a4..b9f32c66 100644
--- a/sources/extension-models/timestamp/TimeStampVersion.xsd
+++ b/sources/extension-models/timestamp/TimeStampVersion.xsd
@@ -68,8 +68,9 @@
                    maxOccurs="unbounded" />
     </xsd:sequence>
     <xsd:attribute name="Version"
+                   default="0"
                    type="sdpi:EpochVersion"
-                   use="required">
+                   use="optional">
       <xsd:annotation>
         <xsd:documentation>Current epoch version. Implied value is 0.</xsd:documentation>
       </xsd:annotation>