Problem with simple xsl:when test expression

        <xsl:choose>
	  <xsl:when test="./restriction[@base='string']">
	  </xsl:when>
        </xsl:choose>

<simpleType name="MedlarsNameString">
  </annotation>
  <restriction base="string">
  </restriction>
</simpleType>

<xsl:template match="xsd:simpleType">
  <xsl:param name="elementName"/>
   <xsl:choose>
      <xsl:when test="@name='TextBlock'">
       Do this....
      </xsl:when>
      <xsl:otherwise>
        <xsl:choose>
	  <xsl:when test="./restriction[@base='string']">
	  Print here.
           </xsl:when>
        </xsl:choose>
      </xsl:otherwise>
    </xsl:choose>
</xsl:template>