variable question

Is there some obvious reason why the "title-before" variable below
doesn't work when called from within a template?

I'm not sure if the problem is that there's something wrong with the
way I'm trying to use variables, or something about the context and the
xpath expressions (my guess is the latter).

<xsl:variable name="reftype">
  <xsl:choose>
    <xsl:when test="not[mods:relatedItem[@type='host']]">
      <xsl:text>book</xsl:text>
    </xsl:when>
    <xsl:when

test="mods:relatedItem[@type='host']/mods:originInfo/mods:
issuance='continuing'">
      <xsl:text>article</xsl:text>
    </xsl:when>
    <xsl:when

test="mods:relatedItem[@type='host']/mods:originInfo/mods:
issuance='monographic'">
      <xsl:text>chapter</xsl:text>
    </xsl:when>
  </xsl:choose>
</xsl:variable>

<xsl:variable name="title-before">
  <xsl:choose>
    <xsl:when test="$reftype='chapter'">
      <xsl:text></xsl:text>
    </xsl:when>
    <xsl:otherwise>
      <xsl:text></xsl:text>
    </xsl:otherwise>
  </xsl:choose>
</xsl:variable>