How to check for atomic item in XPATH?

Question

i would like to check a sequence of Items and report the item type:

• If it is an atomic value (maybe an empty string) report String "A"
• If it is an Element report its local Name
• Otherwise report String "X"

My Question is: How can i check an item to be an atomic value? The only Solution that i found is to use the xs:string(.) function, which takes an anyAtomic as argument. See the following XSLT 3.0 fragment

 <xsl:template match="/*">
    <xsl:variable name="content" as="item()*">
        <xsl:apply-templates select="node()"/>
    </xsl:variable>
    <result>
       <xsl:for-each select="$content">
           <xsl:choose>
               <!-- I`d like to check for any atomic value here -->
               <xsl:when test="xs:string(.)">A</xsl:when>
               <xsl:when test="self::*"><xsl:value-of select="lower-case(local-name())"/></xsl:when>
               <xsl:otherwise>X</xsl:otherwise>
           </xsl:choose>
       </xsl:for-each>
    </result>
</xsl:template>

<xsl:template match="*">
    <xsl:copy/>
</xsl:template>

<xsl:template match="text()" as="xs:string">
    <!-- What if i change to normalize-space(.) ? -->
    <xsl:sequence select="."/>
</xsl:template>

Problem is, that i get an error when i use the normalize-space() function in the template matching text-Node, because in this case the effective boolean value of xs:string() is false for some text Nodes. The following check for the self Axis fails with the error message XPTY0020: The required item type of the context item for the self axis is node(); the supplied value "" is an atomic value.

I have tried with expressions like ". is anyAtomic", but the IS Operator expects Nodes.

I am pretty sure that xs:string(.) is not the correct way to check for atomic items, but what is it?

Thanks, Frank Steimke

Answer 1

XPath has an instance of operator you can use with sequence types so I think you are looking for . instance of xs:anyAtomicType or e.g. . instance of xs:string.