<xsl:if test="string-contains(//ns0:elem/value, 'sth')">


        </xsl:if>
	
<xsl:variable name="alpha" 
              select="'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ'"/>
<xsl:if test="string-length(translate(., $alpha, '')) > 0">
    <!-- context node contains non-alpha characters -->
</xsl:if>
	
<xsl:if test="translate(., $alpha, '')">
	
<xsl:if test="translate(., translate(., $alpha, ''), '')">
    <!-- context-node contains characters on the blacklist (in $alpha) -->
</xsl:if>
	
not(string-length(translate(., $alpha, ''))=string-length())
	
<xsl:if test="translate(., $alpha, '')">
    [contains some characters not on the list]
</xsl:if> 
<xsl:if test="not(translate(., $alpha, ''))">
    [contains only characters on the list]
</xsl:if> 
<xsl:if test="translate(., translate(., $alpha, ''), '')">
    [contains some characters on the list]
</xsl:if>
<xsl:if test="not(translate(., translate(., $alpha, ''), ''))">
    [contains only characters not on the list]
</xsl:if>
	
translate(., translate(., $vAlpha, ''), '')
	
string-length(translate($str, $vAlpha, '')) = 0
	
<xsl:stylesheet version="1.0"
 xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
 <xsl:output method="text"/>

 <xsl:variable name="vUpper" select=
  "'ABCDEFGHIJKLMNOPQRSTUVWXYZ'"/>

 <xsl:variable name="vLower" select=
  "'abcdefghijklmnopqrstuvwxyz'"/>

 <xsl:variable name="vAlpha" select=
      "concat($vUpper, $vLower)"/>

 <xsl:variable name="vStr" select="'A12B_..c02d'"/>

 <xsl:template match="/">
  <xsl:value-of select=
    "translate($vStr,
               translate($vStr, $vAlpha, ''), '')
    "/>


    The string <xsl:value-of select="$vStr"/> has <xsl:text/>
    <xsl:value-of select=
    "string-length(translate($vStr, $vAlpha, ''))"/> <xsl:text/>
    non-letters

 </xsl:template>
</xsl:stylesheet>
	
ABcd


    The string A12B_..c02d has 7
    non-letters