From 5878e797295bc57468e6bfc3f030b5b5fb0c1463 Mon Sep 17 00:00:00 2001
From: Miguel Jimenez-Urias <mjimenez@opendap.org>
Date: Tue, 23 Dec 2025 10:28:03 -0800
Subject: [PATCH] match the spec for structs and seqs when these contain Dim
 elements

---
 dap4/dap4.xsd                  | 36 ++++++++++++++++++++++------------
 tests/data/Structure_test3.dmr | 23 ++++++++++++++++++++++
 2 files changed, 47 insertions(+), 12 deletions(-)
 create mode 100644 tests/data/Structure_test3.dmr

diff --git a/dap4/dap4.xsd b/dap4/dap4.xsd
index f857766..67cf72f 100644
--- a/dap4/dap4.xsd
+++ b/dap4/dap4.xsd
@@ -256,22 +256,34 @@
     </xs:complexType>
 
     <xs:complexType name="StructureType">
-        <xs:complexContent>
-            <xs:extension base="BaseType">
-                <xs:group ref="VariableTypes" minOccurs="1" maxOccurs="unbounded"/>
-            </xs:extension>
-        </xs:complexContent>
+        <xs:annotation>
+            <xs:documentation>A Structure groups a list of variables so that the
+            collection can be manipulated as a single item. The fields (or Variables)
+            in a Structure MAY be of any type, including Structure or Sequence. The 
+            order of items in the Structure is significant only in relation to the 
+            serialized representation of that Structure.</xs:documentation>
+        </xs:annotation>
+        <xs:sequence>
+            <xs:group ref="VariableTypes" minOccurs="1" maxOccurs="unbounded"/>
+            <xs:element ref="Dim" minOccurs="0" maxOccurs="unbounded"/>
+        </xs:sequence>
+        <xs:attribute name="name" type="xs:string"/>
     </xs:complexType>
 
-
-    <xs:complexType name="SequenceType">
-        <xs:complexContent>
-            <xs:extension base="BaseType">
-                <xs:group ref="VariableTypes" minOccurs="1" maxOccurs="unbounded"/>
-            </xs:extension>
-        </xs:complexContent>
+   <xs:complexType name="SequenceType">
+        <xs:annotation>
+            <xs:documentation>A Sequence is intended to represent a sequence of instances of objects.
+            A Sequence was introduced to replace the concept of variable length dimensions.
+            .</xs:documentation>
+        </xs:annotation>
+        <xs:sequence>
+            <xs:group ref="VariableTypes" minOccurs="1" maxOccurs="unbounded"/>
+            <xs:element ref="Dim" minOccurs="0" maxOccurs="unbounded"/>
+        </xs:sequence>
+        <xs:attribute name="name" type="xs:string"/>
     </xs:complexType>
 
+
     <xs:simpleType name="EnumBaseType">
         <xs:restriction base="xs:string">
             <xs:enumeration value="Byte"/>
diff --git a/tests/data/Structure_test3.dmr b/tests/data/Structure_test3.dmr
new file mode 100644
index 0000000..6507de6
--- /dev/null
+++ b/tests/data/Structure_test3.dmr
@@ -0,0 +1,23 @@
+<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
+<Dataset
+         name="test_struct_array.nc"
+         dapVersion="4.0"
+         dmrVersion="1.0"
+         xmlns="http://xml.opendap.org/ns/DAP/4.0#"
+         xmlns:dap="http://xml.opendap.org/ns/DAP/4.0#">
+    <Structure name="s">
+        <Int32 name="x"/>
+        <Int32 name="y"/>
+        <Dim size="2"/>
+        <Dim size="2"/>
+    </Structure>
+    <Attribute name="_dap4.ce" type="String">
+        <Value value="/s[0:2:3][0:1]"/>
+    </Attribute>
+    <Attribute name="_DAP4_Little_Endian" type="UInt8">
+        <Value value="1"/>
+    </Attribute>
+    <Attribute name="_NCProperties" type="String">
+        <Value value="version=2,netcdf=4.9.1-development,hdf5=1.12.2"/>
+    </Attribute>
+</Dataset>
\ No newline at end of file