A problem with concat()

Hi all,
Thanks for reading. I'm sure I'm making an error, but I'm not able to
determine where I'm going awry.

I want to use concat() to pull together three elements, separating the
values with a comma. I've done this, but it turns out that I need to
test the elements. When I perform the tests I'm able to concat() the
values (when appropriate), but I'm not getting any commas between my
values. I put up examples on pastebin: the XML is at
http://pastebin.com/tGbJMpGG and the XSLT is at
http://pastebin.com/DY4ELbh3, lines 11-18 and 25-58 respectively. The
examples below are shortened versions of the examples on Pastebin -
line numbers will be slightly different.

Thanks for your time and suggestions.
Cheers,
Bridger

PS here is an abbreviated example of the XML and the XSLT:

<?xml version="1.0" encoding="UTF-8"  ?>
<mods:mods xmlns:mods="http://www.loc.gov/mods/v3"
 xmlns:xlink="http://www.w3.org/1999/xlink"
 xmlns="http://www.loc.gov/mods/v3"
 xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
 xsi:schemaLocation="http://www.loc.gov/mods/v3
 http://www.loc.gov/standards/mods/v3/mods-3-2.xsd" ID="MODS" version="3.2">
  <mods:titleInfo>
    <mods:title>Chimney and Indian Gap Hotel</mods:title>
  </mods:titleInfo>
  <mods:name  type="personal" authority="LCNAF">
    <mods:namePart type="family">Thompson</mods:namePart>
    <mods:namePart type="given">James Edward</mods:namePart>
    <mods:namePart type="date">1880-1976</mods:namePart>
    <mods:role>
      <mods:roleTerm authority="marcrelator">Photographer</mods:roleTerm>
    </mods:role>
  </mods:name>
</mods:mods>

<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
version="2.0"
    xmlns:mods="http://www.loc.gov/mods/v3"
xmlns:xlink="http://www.w3.org/1999/xlink"
    xmlns="http://www.loc.gov/mods/v3"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://www.loc.gov/mods/v3
    http://www.loc.gov/standards/mods/v3/mods-3-2.xsd"
    xmlns:oai_dc="http://www.openarchives.org/OAI/2.0/oai_dc/"
    xmlns:dc="http://purl.org/dc/elements/1.1/">

    <xsl:output method="xml" media-type="text/xml" indent="yes" />
    <xsl:strip-space elements="*"/>
    <xsl:template match="mods:mods">
        <oai_dc
            xsi:schemaLocation="http://www.openarchives.org/OAI/2.0/oai_dc/
http://www.openarchives.org/OAI/2.0/oai_dc.xsd">
            <xsl:apply-templates/>
        </oai_dc>
    </xsl:template>

    <xsl:template match="mods:titleInfo">
        <dc:title>
            <xsl:value-of select="./mods:title"/>
        </dc:title>
    </xsl:template>

    <xsl:template match="mods:name">
        <xsl:choose>
            <xsl:when test="./mods:role/mods:roleTerm">
                <dc:creator>
                    <!--<xsl:value-of
select="concat(./mods:namePart[@type='family'], ', ',
./mods:namePart[@type='given'], ', ',
./mods:namePart[@type='date'])"/>-->
                    <xsl:choose>
                        <xsl:when test="not(@attribute)">
                            <xsl:value-of select="mods:namePart"/>
                        </xsl:when>
                        <xsl:otherwise>
                            <xsl:choose>
                                <xsl:when test=".[@type='corporate']">
                                    <xsl:value-of select="mods:namePart"/>
                                </xsl:when>
                                <xsl:when test=".[@type='personal']">
                                    <xsl:if test="count(mods:namePart) = 1">
                                        <xsl:value-of
select="mods:namePart"/>
                                    </xsl:if>
                                    <xsl:if test="count(mods:namePart) > 2">
                                        <xsl:value-of
select="concat(./mods:namePart[@type='family'], ', ',
./mods:namePart[@type='given'], ', ',
./mods:namePart[@type='date'])"/>
                                    </xsl:if>
                                </xsl:when>
                            </xsl:choose>
                        </xsl:otherwise>
                    </xsl:choose>
                </dc:creator>
            </xsl:when>
            <xsl:otherwise>
                <dc:contributor>
                    <xsl:value-of select="./mods:namePart[@type='*']"/>
                </dc:contributor>
            </xsl:otherwise>
        </xsl:choose>
    </xsl:template>


</xsl:stylesheet>