diff --git a/XML_schema/NDAttributes.xsd b/XML_schema/NDAttributes.xsd
index 80209ccc1..75da25a60 100644
--- a/XML_schema/NDAttributes.xsd
+++ b/XML_schema/NDAttributes.xsd
@@ -179,6 +179,10 @@
   </xs:simpleType>
   
   <xs:simpleType name="type_source">
+    <xs:union memberTypes="type_EPICS_PV_source type_PARAM_source"/>
+  </xs:simpleType>
+  
+  <xs:simpleType name="type_EPICS_PV_source">
     <!-- EPICS PV name rules
       see: http://www.aps.anl.gov/epics/wiki/index.php/RRM_3-14_Concepts#Database_Addresses
       The record name can be a mix of the following: 
@@ -189,13 +193,11 @@
       BUT, cannot express "<" in XML, must use &lt; but that won't parse!
       So, use use a reduced (but very likely) subset of rules.  
       Do not allow these symbols: []<>
+
+      To support macro expansion, support these symbols: $ ( )
     -->
-    <xs:union memberTypes="type_EPICS_PV_source type_PARAM_source"/>
-  </xs:simpleType>
-  
-  <xs:simpleType name="type_EPICS_PV_source">
-    <xs:restriction base="xs:NMTOKEN">
-      <xs:pattern value="[\w_\-:.;]+([.][A-Z0-9]+)?"/>
+    <xs:restriction base="xs:string">
+      <xs:pattern value="[\w_\-:.;\$\(\)]+([.][A-Z0-9]+)?"/>
     </xs:restriction>
   </xs:simpleType>
   
diff --git a/XML_schema/example_attributes.xml b/XML_schema/example_attributes.xml
new file mode 100755
index 000000000..899de743f
--- /dev/null
+++ b/XML_schema/example_attributes.xml
@@ -0,0 +1,15 @@
+<?xml version="1.0" standalone="no" ?>
+<!-- Attributes -->
+<Attributes
+    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+    xsi:noNamespaceSchemaLocation="https://github.com/areaDetector/ADCore/blob/master/iocBoot/NDAttributes.xsd"
+    >
+    <Attribute name="AcquireTime"         type="EPICS_PV" source="13SIM1:cam1:AcquireTime"      dbrtype="DBR_NATIVE"  description="Camera acquire time"/>
+    <Attribute name="ImageCounter"        type="PARAM"    source="ARRAY_COUNTER"                datatype="INT"        description="Image counter"/>
+    <Attribute name="calc1_val"           type="EPICS_PV" source="$(P)userCalc1.VAL"            dbrtype="DBR_NATIVE" description="some calculation result"/>
+    <Attribute name="calc2_val"           type="EPICS_PV" source="$(P)userCalc2.VAL"            dbrtype="DBR_NATIVE" description="another calculation result"/>
+    <Attribute name="MaxSizeX"            type="PARAM"    source="MAX_SIZE_X"                   datatype="INT"        description="Detector X size"/>
+    <Attribute name="MaxSizeY"            type="PARAM"    source="MAX_SIZE_Y"                   datatype="INT"        description="Detector Y size"/>
+    <Attribute name="CameraModel"         type="PARAM"    source="MODEL"                        datatype="STRING"     description="Camera model"/>
+    <Attribute name="CameraManufacturer"  type="PARAM"    source="MANUFACTURER"                 datatype="STRING"     description="Camera manufacturer"/>
+</Attributes>