Question

am trying to flatten an XML element based on a child element name using XSLT 1.0

The source XML:

<Contact>
  <ContactPurpose>
    <PurposeAsPlainText xmlns="cds_dt">Call</PurposeAsPlainText>
  </ContactPurpose>
  <ContactPurpose>
    <PurposeAsEnum xmlns="cds_dt">Call</PurposeAsEnum>
  </ContactPurpose>
</Contact>

Should be transformed into the following XML:

<Contact>
  <ContactPurpose>O</ContactPurpose>
  <ContactPurpose>Call</ContactPurpose>
</Contact>

The Logic is:

IF the child element name is “PurposeAsPlainText “ THEN
set “O” for Other in destination

ELSEIF the child element name is “PurposeAsEnum” THEN
copy the source value to destination

EDIT 1: I could be more clear as none of the solutions flattened the xml, please see revised source and dest XML.

EDIT 2: Here is the XML I was testing against. The two tranform solutions below actually do work on my original xml but not the revised xml that I was testing using .NET 4.0 XslCompiledTransform. Or should I make a new question?

<MyDS xmlns="cds" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema">
  <PatientRecord>
    <Demographics>
      <Contact>
        <ContactPurpose>
          <PurposeAsPlainText xmlns="cds_dt">Call</PurposeAsPlainText>
        </ContactPurpose>
        <ContactPurpose>
          <PurposeAsEnum xmlns="cds_dt">Call</PurposeAsEnum>
        </ContactPurpose>
      </Contact>
    </Demographics>
  </PatientRecord>
</MyDS>

Answer 1

This can be done in a simple and short way (no explicit conditionals):

<xsl:stylesheet version="1.0"
 xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
 xmlns:x="cds_dt" exclude-result-prefixes="x">
 <xsl:output omit-xml-declaration="yes" indent="yes"/>
 <xsl:strip-space elements="*"/>

 <xsl:template match="node()|@*">
     <xsl:copy>
       <xsl:apply-templates select="node()|@*"/>
     </xsl:copy>
 </xsl:template>

 <xsl:template match="ContactPurpose/x:PurposeAsPlainText/text()">0</xsl:template>

 <xsl:template match="ContactPurpose/*"><xsl:apply-templates/></xsl:template>
</xsl:stylesheet>

when applied to the following XML document (extended to encorporate both cases of interest):

<Contact>
    <ContactPurpose>
        <PurposeAsPlainText xmlns="cds_dt">Call</PurposeAsPlainText>
    </ContactPurpose>
    <ContactPurpose>
        <PurposeAsEnum xmlns="cds_dt">Call</PurposeAsEnum>
    </ContactPurpose>
</Contact>

produces the wanted, correct result:

<Contact>
   <ContactPurpose>0</ContactPurpose>
   <ContactPurpose>Call</ContactPurpose>
</Contact>

Explanation:

Overriding the identity rule and appropriate use of templates/match patterns.

Update: The OP has modified his XML document, which is now in a default namespace:

<MyDS xmlns="cds" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:xsd="http://www.w3.org/2001/XMLSchema">
    <PatientRecord>
        <Demographics>
            <Contact>
                <ContactPurpose>
                    <PurposeAsPlainText xmlns="cds_dt">Call</PurposeAsPlainText>
                </ContactPurpose>
                <ContactPurpose>
                    <PurposeAsEnum xmlns="cds_dt">Call</PurposeAsEnum>
                </ContactPurpose>
            </Contact>
        </Demographics>
    </PatientRecord>
</MyDS>

Accordingly, here is a slightly modified transformation that produces the wanted result:

<xsl:stylesheet version="1.0"
     xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
     xmlns:x="cds_dt" xmlns:c="cds" exclude-result-prefixes="c x">
     <xsl:output omit-xml-declaration="yes" indent="yes"/>
     <xsl:strip-space elements="*"/>

     <xsl:template match="node()|@*">
         <xsl:copy>
           <xsl:apply-templates select="node()|@*"/>
         </xsl:copy>
     </xsl:template>

     <xsl:template match="c:ContactPurpose/x:PurposeAsPlainText/text()">0</xsl:template>

     <xsl:template match="c:ContactPurpose/*"><xsl:apply-templates/></xsl:template>
</xsl:stylesheet>

When this transformation is applied on the new XML document (closest above), the new wanted, correct result is produced:

<MyDS xmlns="cds" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:xsd="http://www.w3.org/2001/XMLSchema">
   <PatientRecord>
      <Demographics>
         <Contact>
            <ContactPurpose>0</ContactPurpose>
            <ContactPurpose>Call</ContactPurpose>
         </Contact>
      </Demographics>
   </PatientRecord>
</MyDS>