XSD: Extending Code Lists with xsd:union

In certain circumstances it is necessary to add elements to an existing NIEM enumeration (or code list).  In these situations one may choose to simply recreate a new list with all the same elements already defined in a NIEM code type and simply add those which do not yet exist.  However, when the code list is larger than a few elements (such as a state code list with at least 50 valid values), using xsd:union as an option becomes more appealing.

The xsd:union provides a way to combine simple data types together to form a larger and more comprehensive data type.  An example would be simply adding “ZZ” to a list of US Postal Service State (USPS) Codes to communicate an unknown or invalid state.  This can be accomplished by extending the existing USPS code list in several steps.

Step 1 – Create a New Simple Type With New Values

<!-- Simple code value to add ZZ as a valid value -->
<xsd:simpletype name="USStateCodeDefaultSimpleType">
  <xsd:restriction base="xsd:token">
   <xsd:enumeration value="ZZ">
    <xsd:annotation>
     <xsd:documentation>UNKNOWN</xsd:documentation>
    </xsd:annotation>
   </xsd:enumeration>
  </xsd:restriction>
</xsd:simpletype>

Step 2 – Use xsd:union to Join the Values with Existing Values

<!-- New simple time combining my custom enum with the standard usps one --> 
<xsd:simpleType name="LocationStateCodeSimpleType">
  <xsd:union memberTypes="usps:USStateCodeSimpleType my:USStateCodeDefaultSimpleType"/>
</xsd:simpleType>

Step 3 – Wrap the New Simple Data Type in a Complex Type

<!-- New complexType required to add s:id and s:idref to the definition -->
<xsd:complexType name="LocationStateCodeType">
  <xsd:simpleContent>
    <xsd:extension base="aoc_code:LocationStateCodeSimpleType"> 
      <xsd:attributeGroup ref="s:SimpleObjectAttributeGroup"/>
    </xsd:extension>
  </xsd:simpleContent>
</xsd:complexType>

Step 4 – Create Element Instantiating the New Code List

<!-- Element declaration allowing use of our new data type -->
<xsd:element name="NewStateCode" type="my:LocationStateCodeType" substitutionGroup="nc:LocationStateCode"/>

Now any place an nc:LocationStateCode can be use, our extended code list can be used instead.

XSLT: Convert Standard U.S. Date into xsd:date Format

When working with XML in the United States (U.S.), one will often find dates which have been formatted in the traditional U.S. Short Format even though XML Schema (XSD) enforces a more locale-neutral format.  This means often converting data from:

<SomeUsDate>1/10/2001</SomeUsDate>

Into:

<SomeXsdDate>2001-01-10</SomeXsdDate>

If one is using XSLT 2.0, this can simply be done by including and calling the function within the FunctX library here. 

In XSLT 1.0, a very limited set of string manipulation functionality exists. Even so, it is possible (although convoluted) to convert a typical U.S.-formatted date into an XML-Schema enforced date. A possible solution is listed below:

<xsl:template name="aoc:txfDateFormat">
         <xsl:param name="UsDate"/>

         <xsl:choose>

             <!-- Test to see if date contains a date with slashes in it. -->
             <xsl:when test="contains($UsDate, '/')">
                 <xsl:choose>

                     <!-- 2 Digit Month, 2 Digit Day -->
                     <xsl:when
                         test="string-length(substring-before($UsDate, '/'))=2 and (string-length(substring-before(substring-after($UsDate, '/'), '/'))=2)">
                         <nc:Date>
                             <xsl:value-of
                                 select="concat(substring-after(substring-after($UsDate, '/'), '/'),'-',substring-before($UsDate, '/'), '-', substring-before(substring-after($UsDate, '/'), '/'))"
                             />
                         </nc:Date>
                     </xsl:when>

                     <!-- 1 Digit Month, 2 Digit Day -->
                     <xsl:when
                         test="string-length(substring-before($UsDate, '/'))=1 and (string-length(substring-before(substring-after($UsDate, '/'), '/'))=2)">
                         <nc:Date>
                             <xsl:value-of
                                 select="concat(substring-after(substring-after($UsDate, '/'), '/'),'-0',substring-before($UsDate, '/'), '-', substring-before(substring-after($UsDate, '/'), '/'))"
                             />
                         </nc:Date>
                     </xsl:when>

                     <!-- 2 Digit Month, 1 Digit Day -->
                     <xsl:when
                         test="string-length(substring-before($UsDate, '/'))=2 and (string-length(substring-before(substring-after($UsDate, '/'), '/'))=1)">
                         <nc:Date>
                             <xsl:value-of
                                 select="concat(substring-after(substring-after($UsDate, '/'), '/'),'-',substring-before($UsDate, '/'), '-0', substring-before(substring-after($UsDate, '/'), '/'))"
                             />
                         </nc:Date>
                     </xsl:when>

                     <!-- 1 Digit Month, 1 Digit Day -->
                     <xsl:when
                         test="string-length(substring-before($UsDate, '/'))=1 and (string-length(substring-before(substring-after($UsDate, '/'), '/'))=1)">
                         <nc:Date>
                             <xsl:value-of
                                 select="concat(substring-after(substring-after($UsDate, '/'), '/'),'-0',substring-before($UsDate, '/'), '-0', substring-before(substring-after($UsDate, '/'), '/'))"
                             />
                         </nc:Date>
                     </xsl:when>
                 </xsl:choose>
             </xsl:when>

             <!-- Omit element if not. -->
             <xsl:otherwise/>
         </xsl:choose>
   </xsl:template>