<?xml version="1.0" encoding="UTF-8"?>
<xsd:schema version="5.0" 
            xmlns:nwis="http://water.usgs.gov/XML/NWIS/5.0"
            
            xmlns:xsd="http://www.w3.org/2001/XMLSchema"
            
            elementFormDefault="qualified">
   <xsd:simpleType name="HexValueType">
      <xsd:restriction base="xsd:string">
         <xsd:pattern value="[0-9A-F]+"/>
         <xsd:minLength value="8"/>
         <xsd:maxLength value="8"/>
      </xsd:restriction>
   </xsd:simpleType>
</xsd:schema>