diff --git a/iocBoot/NeXus_templates.xsd b/iocBoot/NeXus_templates.xsd
index 5c3e5b3..a6aec01 100755
--- a/iocBoot/NeXus_templates.xsd
+++ b/iocBoot/NeXus_templates.xsd
@@ -24,228 +24,158 @@
   <xs:element name="NXroot" >
     <xs:complexType>
       <xs:sequence>
-        <xs:element ref="Facility"/>
-        <xs:element ref="NXentry"/>
+        <xs:element ref="Facility" minOccurs="0"/>  <!-- not recommended for new projects -->
+        <xs:element ref="NXentry" maxOccurs="unbounded"/>
       </xs:sequence>
-      <xs:attributeGroup ref="common_attributes"/>
+      <xs:attribute name="name" type="type_NeXus_name" />
     </xs:complexType>
   </xs:element>
+
   <xs:element name="Facility">
+    <!-- legacy group from CCDImageServer, not a NeXus group and ignored -->
     <xs:complexType>
       <xs:sequence>
-        <xs:element ref="facility_name"/>
-        <xs:element ref="facility_sector"/>
-        <xs:element ref="facility_beamline"/>
-        <xs:element ref="facility_station"/>
-        <xs:element ref="facility_float"/>
-        <xs:element ref="facility_int"/>
+        <xs:element name="facility_name" type="commonElement"/>
+        <xs:element name="facility_sector" type="commonElement"/>
+        <xs:element name="facility_beamline" type="commonElement"/>
+        <xs:element name="facility_station" type="commonElement"/>
+        <xs:element name="facility_float" type="commonElement"/>
+        <xs:element name="facility_int" type="commonElement"/>
       </xs:sequence>
-      <xs:attribute name="type" use="required" type="xs:NCName"/>
-    </xs:complexType>
-  </xs:element>
-  <xs:element name="facility_name">
-    <xs:complexType>
-      <xs:simpleContent>
-        <xs:extension base="xs:NCName">
-          <xs:attribute name="outtype" use="required" type="xs:NCName"/>
-          <xs:attribute name="type" use="required" type="xs:NCName"/>
-        </xs:extension>
-      </xs:simpleContent>
-    </xs:complexType>
-  </xs:element>
-  <xs:element name="facility_sector">
-    <xs:complexType mixed="true">
-      <xs:attribute name="outtype" use="required" type="xs:NCName"/>
-      <xs:attribute name="type" use="required" type="xs:NCName"/>
-    </xs:complexType>
-  </xs:element>
-  <xs:element name="facility_beamline">
-    <xs:complexType>
-      <xs:simpleContent>
-        <xs:extension base="xs:NMTOKEN">
-          <xs:attribute name="outtype" use="required" type="xs:NCName"/>
-          <xs:attribute name="type" use="required" type="xs:NCName"/>
-        </xs:extension>
-      </xs:simpleContent>
-    </xs:complexType>
-  </xs:element>
-  <xs:element name="facility_station">
-    <xs:complexType>
-      <xs:simpleContent>
-        <xs:extension base="xs:NCName">
-          <xs:attribute name="outtype" use="required" type="xs:NCName"/>
-          <xs:attribute name="type" use="required" type="xs:NCName"/>
-        </xs:extension>
-      </xs:simpleContent>
-    </xs:complexType>
-  </xs:element>
-  <xs:element name="facility_float">
-    <xs:complexType>
-      <xs:simpleContent>
-        <xs:extension base="xs:decimal">
-          <xs:attribute name="outtype" use="required" type="xs:NCName"/>
-          <xs:attribute name="type" use="required" type="xs:NCName"/>
-        </xs:extension>
-      </xs:simpleContent>
-    </xs:complexType>
-  </xs:element>
-  <xs:element name="facility_int">
-    <xs:complexType>
-      <xs:simpleContent>
-        <xs:extension base="xs:integer">
-          <xs:attribute name="outtype" use="required" type="xs:NCName"/>
-          <xs:attribute name="type" use="required" type="xs:NCName"/>
-        </xs:extension>
-      </xs:simpleContent>
+      <xs:attribute name="type" use="required" fixed="UserGroup"/>
     </xs:complexType>
   </xs:element>
+
   <xs:element name="NXentry">
     <xs:complexType>
       <xs:sequence>
-        <xs:element ref="title"/>
-        <xs:element ref="experiment_identifier"/>
-        <xs:element ref="experiment_description"/>
-        <xs:element ref="experiment_documentation"/>
-        <xs:element ref="collection_identifier"/>
-        <xs:element ref="collection_description"/>
-        <xs:element ref="entry_identifier"/>
-        <xs:element ref="definition"/>
-        <xs:element ref="start_time"/>
-        <xs:element ref="end_time"/>
-        <xs:element ref="duration"/>
-        <xs:element ref="collection_time"/>
-        <xs:element ref="run_cycle"/>
-        <xs:element ref="program_name"/>
-        <xs:element ref="revision"/>
-        <xs:element ref="notes"/>
-        <xs:element ref="NXuser"/>
-        <xs:element ref="NXdata"/>
-        <xs:element ref="NXinstrument"/>
-        <xs:element minOccurs="0" ref="NXcollection"/>
+        <xs:element name="title" type="commonElement"/>
+        <xs:element name="experiment_identifier" type="commonElement"/>
+        <xs:element name="experiment_description" type="commonElement"/>
+        <xs:element name="experiment_documentation" type="commonElement"/>
+        <xs:element name="collection_identifier" type="commonElement"/>
+        <xs:element name="collection_description" type="commonElement"/>
+        <xs:element name="entry_identifier" type="commonElement"/>
+        <xs:element name="definition" type="commonElement"/>
+        <xs:element name="start_time" type="commonElement"/>
+        <xs:element name="end_time" type="commonElement"/>
+        <xs:element name="duration" type="commonElement"/>
+        <xs:element name="collection_time" type="commonElement"/>
+        <xs:element name="run_cycle" type="commonElement"/>
+        <xs:element name="program_name" type="commonElement"/>
+        <xs:element name="revision" type="commonElement"/>
+        <xs:element name="notes" type="commonElement"/>
+        <xs:element ref="NXuser" minOccurs="0"/>
+        <xs:element ref="NXdata" minOccurs="1" maxOccurs="unbounded"/>
+        <xs:element ref="NXinstrument" minOccurs="0"/>
+        <xs:element ref="NXcollection" minOccurs="0"/>
       </xs:sequence>
-      <xs:attributeGroup ref="common_attributes"/>
+      <xs:attribute name="name" type="type_NeXus_name" />
     </xs:complexType>
   </xs:element>
-  <xs:element name="title" type="commonElement"/>
-  <xs:element name="experiment_identifier" type="commonElement"/>
-  <xs:element name="experiment_description" type="commonElement"/>
-  <xs:element name="experiment_documentation" type="commonElement"/>
-  <xs:element name="collection_identifier" type="commonElement"/>
-  <xs:element name="collection_description" type="commonElement"/>
-  <xs:element name="entry_identifier" type="commonElement"/>
-  <xs:element name="definition" type="commonElement"/>
-  <xs:element name="start_time" type="commonElement"/>
-  <xs:element name="end_time" type="commonElement"/>
-  <xs:element name="duration" type="commonElement"/>
-  <xs:element name="collection_time" type="commonElement"/>
-  <xs:element name="run_cycle" type="commonElement"/>
-  <xs:element name="program_name" type="commonElement"/>
-  <xs:element name="revision" type="commonElement"/>
-  <xs:element name="notes" type="commonElement"/>
+
   <xs:element name="NXuser">
     <xs:complexType>
       <xs:sequence>
-        <xs:element ref="name"/>
-        <xs:element ref="role"/>
-        <xs:element ref="affiliation"/>
-        <xs:element ref="address"/>
-        <xs:element ref="telephone_number"/>
-        <xs:element ref="fax_number"/>
-        <xs:element ref="email"/>
-        <xs:element ref="facility_user_id"/>
+        <xs:element name="name" type="commonElement"/>
+        <xs:element name="role" type="commonElement"/>
+        <xs:element name="affiliation" type="commonElement"/>
+        <xs:element name="address" type="commonElement"/>
+        <xs:element name="telephone_number" type="commonElement"/>
+        <xs:element name="fax_number" type="commonElement"/>
+        <xs:element name="email" type="commonElement"/>
+        <xs:element name="facility_user_id" type="commonElement"/>
       </xs:sequence>
-      <xs:attributeGroup ref="common_attributes"/>
+      <xs:attribute name="name" type="type_NeXus_name" />
     </xs:complexType>
   </xs:element>
-  <xs:element name="role" type="commonElement"/>
-  <xs:element name="affiliation" type="commonElement"/>
-  <xs:element name="address" type="commonElement"/>
-  <xs:element name="telephone_number" type="commonElement"/>
-  <xs:element name="fax_number" type="commonElement"/>
-  <xs:element name="email" type="commonElement"/>
-  <xs:element name="facility_user_id" type="commonElement"/>
+
   <xs:element name="NXdata">
     <xs:complexType>
       <xs:sequence>
-        <xs:element ref="maxSizeX"/>
-        <xs:element ref="maxSizeY"/>
-        <xs:element ref="make"/>
-        <xs:element ref="model"/>
-        <xs:element minOccurs="0" ref="ImageCounter"/>
-        <xs:element ref="data"/>
+        <xs:element name="maxSizeX" type="commonElement"/>
+        <xs:element name="maxSizeY" type="commonElement"/>
+        <xs:element name="make" type="commonElement"/>
+        <xs:element name="model" type="commonElement"/>
+        <xs:element name="ImageCounter" type="commonElement" minOccurs="0" />
+        <!-- TODO: special attention needed here
+          This sets the name of the data to "data" which is not required by NeXus.
+          Also, it is necessary to require a signal="1" attribute definition
+          for only one dataset in the NXdata group:
+          <Attr name="signal" type="CONST" outtype="NX_CHAR">1</Attr>
+          
+          Perhaps we need to switch from XML Schema to Schematron to validate template.xml files?
+        -->
+        <xs:element name="data" type="dataElement"/>
       </xs:sequence>
-      <xs:attributeGroup ref="common_attributes"/>
+      <xs:attribute name="name" type="type_NeXus_name" />
     </xs:complexType>
   </xs:element>
-  <xs:element name="maxSizeX" type="commonElement"/>
-  <xs:element name="maxSizeY" type="commonElement"/>
-  <xs:element name="make" type="commonElement"/>
-  <xs:element name="model" type="commonElement"/>
-  <xs:element name="ImageCounter" type="commonElement"/>
-  <xs:element name="data" type="commonElement"/>
+
   <xs:element name="NXinstrument">
     <xs:complexType>
       <xs:sequence minOccurs="0">
         <xs:element ref="NXinsertion_device"/>
         <xs:element ref="NXsource"/>
       </xs:sequence>
-      <xs:attributeGroup ref="common_attributes"/>
+      <xs:attribute name="name" type="type_NeXus_name" />
     </xs:complexType>
   </xs:element>
+
   <xs:element name="NXinsertion_device">
     <xs:complexType>
       <xs:sequence>
-        <xs:element ref="type"/>
-        <xs:element ref="energy"/>
+        <xs:element name="type" type="commonElement"/>
+        <xs:element name="energy" type="commonElement"/>
       </xs:sequence>
-      <xs:attributeGroup ref="common_attributes"/>
+      <xs:attribute name="name" type="type_NeXus_name" />
     </xs:complexType>
   </xs:element>
-  <xs:element name="energy" type="commonElement"/>
+
   <xs:element name="NXsource">
     <xs:complexType>
       <xs:sequence>
-        <xs:element ref="name"/>
-        <xs:element ref="type"/>
-        <xs:element ref="probe"/>
-        <xs:element ref="current"/>
-        <xs:element ref="top_up"/>
+        <xs:element name="name" type="commonElement"/>
+        <xs:element name="type" type="commonElement"/>
+        <xs:element name="probe" type="commonElement"/>
+        <xs:element name="current" type="commonElement"/>
+        <xs:element name="top_up" type="commonElement"/>
       </xs:sequence>
-      <xs:attributeGroup ref="common_attributes"/>
+      <xs:attribute name="name" type="type_NeXus_name" />
     </xs:complexType>
   </xs:element>
-  <xs:element name="probe" type="commonElement"/>
-  <xs:element name="current" type="commonElement"/>
-  <xs:element name="top_up" type="commonElement"/>
+
   <xs:element name="NXcollection">
     <xs:complexType>
       <xs:sequence>
-        <xs:element ref="beamline"/>
+        <xs:element name="beamline" type="commonElement"/>
       </xs:sequence>
-      <xs:attributeGroup ref="common_attributes"/>
+      <xs:attribute name="name" type="type_NeXus_name" />
     </xs:complexType>
   </xs:element>
-  <xs:element name="beamline" type="xs:NMTOKEN"/>
-  <xs:element name="name" type="commonElement"/>
-  <xs:element name="type" type="commonElement"/>
+  
+  <!-- ++++++++++++++++++++++++++++++++++++++++++++++++++++++++ -->
   
   <xs:complexType name="commonElement" mixed="true">
     <xs:group ref="Attr_group"/>
     <xs:attributeGroup ref="common_attributes"/>
   </xs:complexType>
-
+  
+  <xs:complexType name="dataElement" mixed="true">
+    <xs:group ref="Attr_group"/>
+    <xs:attributeGroup ref="data_attributes"/>
+  </xs:complexType>
+  
   <xs:attributeGroup name="common_attributes">
-    <xs:attribute name="name" type="xs:NCName"/>
-    <xs:attribute name="type">
-      <xs:simpleType>
-        <xs:restriction base="xs:string">
-          <xs:enumeration value="ATTR"/>
-          <xs:enumeration value="CONST"/>
-          <xs:enumeration value="ND_ATTR"/>
-          <xs:enumeration value="pArray"/>
-        </xs:restriction>
-      </xs:simpleType>
-    </xs:attribute>
+    <xs:attribute name="name" type="type_NeXus_name"/>
+    <xs:attribute name="type" type="type_basic_values"/>
+    <xs:attribute name="outtype" type="xs:string"/>
+    <xs:attribute name="source" type="xs:string"/>
+  </xs:attributeGroup>
+  
+  <xs:attributeGroup name="data_attributes">
+    <xs:attribute name="name" type="type_NeXus_name"/>
+    <xs:attribute name="type" type="type_basic_values_and_pArray"/>
     <xs:attribute name="outtype" type="xs:string"/>
     <xs:attribute name="source" type="xs:string"/>
   </xs:attributeGroup>
@@ -254,21 +184,66 @@
     <xs:sequence>
       <xs:element name="Attr" minOccurs="0" maxOccurs="unbounded">
         <xs:complexType mixed="true">
-          <xs:attribute name="name" type="xs:NCName"/>
+          <xs:attribute name="name" type="type_NeXus_name"/>
           <xs:attribute name="outtype" type="xs:string"/>
-          <xs:attribute name="source"></xs:attribute>
-          <xs:attribute name="type" use="required">
-            <xs:simpleType>
-              <xs:restriction base="xs:string">
-                <xs:enumeration value="ATTR"/>
-                <xs:enumeration value="CONST"/>
-                <xs:enumeration value="ND_ATTR"/>
-              </xs:restriction>
-            </xs:simpleType>
-          </xs:attribute>
+          <xs:attribute name="source" type="type_source"/>
+          <xs:attribute name="type" use="required" type="type_basic_values"/>
         </xs:complexType>
       </xs:element>
     </xs:sequence>
   </xs:group>
+  
+  <!-- There are only two kinds values allowed for the "type" attribute -->
+  
+  <xs:simpleType name="type_basic_values_and_pArray">
+    <xs:union memberTypes="type_pArray type_ATTR type_CONST type_ND_ATTR"/>
+  </xs:simpleType>
+  
+  <xs:simpleType name="type_basic_values">
+    <xs:union memberTypes="type_ATTR type_CONST type_ND_ATTR"/>
+  </xs:simpleType>
+  
+  <!-- These definitions look simplistic, here's why:
+    Define each term here with the text appearing only once,
+    then every instance using the definition can be validated
+    for correct spelling.
+  -->
+  <xs:simpleType name="type_pArray">
+    <xs:restriction base="xs:string">
+      <xs:enumeration value="pArray"/>
+    </xs:restriction>
+  </xs:simpleType>
+  
+  <xs:simpleType name="type_ATTR">
+    <xs:restriction base="xs:string">
+      <xs:enumeration value="ATTR"/>
+    </xs:restriction>
+  </xs:simpleType>
+  
+  <xs:simpleType name="type_CONST">
+    <xs:restriction base="xs:string">
+      <xs:enumeration value="CONST"/>
+    </xs:restriction>
+  </xs:simpleType>
+  
+  <xs:simpleType name="type_ND_ATTR">
+    <xs:restriction base="xs:string">
+      <xs:enumeration value="ND_ATTR"/>
+    </xs:restriction>
+  </xs:simpleType>
+  
+  <xs:simpleType name="type_source">
+    <!-- must match rule for "name" attribute in attributes.xsd -->
+    <xs:restriction base="xs:token">
+      <xs:pattern value="[A-Za-z_][\w_]*" />
+    </xs:restriction>
+  </xs:simpleType>
+  
+  <xs:simpleType name="type_NeXus_name">
+    <xs:restriction base="xs:token">
+      <xs:pattern value="[A-Za-z_][\w_]*" /> <!-- NeXus restrictions to HDF5 naming rule -->
+      <xs:maxLength value="63" /> <!-- HDF5 rule -->
+    </xs:restriction>
+  </xs:simpleType>
 
 </xs:schema>
diff --git a/iocBoot/attributes.xsd b/iocBoot/attributes.xsd
index f0997e3..f0f4f4c 100644
--- a/iocBoot/attributes.xsd
+++ b/iocBoot/attributes.xsd
@@ -94,6 +94,7 @@
       </xs:annotation>
     </xs:attribute>
     <xs:attribute name="name" use="required">
+      <!-- must match rule for "source" attribute in NeXus_templates.xsd -->
       <xs:annotation>
         <xs:documentation>
           One-word mnemonic reference that determines the name of the NDAttribute.