AB-xslt-093

The pipeline

<p:declare-step xmlns:p="http://www.w3.org/ns/xproc" version="3.0">
   <p:output port="result"/>
   <p:xslt version="3.0">
      <p:with-input>
         <doc att="present"/>
         <doc2/>
      </p:with-input>
      <p:with-input port="stylesheet">
         <xsl:stylesheet xmlns:xs="http://www.w3.org/2001/XMLSchema" xmlns:xsl="http://www.w3.org/1999/XSL/Transform" version="3.0">
            <xsl:variable name="gci" as="xs:string?">
               <xsl:try>
                  <xsl:sequence select="./doc/@att"/>
                  <xsl:catch>
                     <xsl:value-of select="'absent'"/>
                  </xsl:catch>
               </xsl:try>
            </xsl:variable>
            <xsl:template match="/">
               <result>
                  <xsl:value-of select="$gci"/>
               </result>
            </xsl:template>
         </xsl:stylesheet>
      </p:with-input>
   </p:xslt>
   <p:wrap-sequence wrapper="wrapper"/>
</p:declare-step>