XSLT problem: The required item type of the first operand of '/' is node(); the supplied value xs:base64Binary is an atomic value

so I'm having weird problems with an XSL transformation.

I am trying to get distinct values from files in a folder.

• Path to objects in folder: <xsl:variable name="objects" select="collection('../../../../data/objects')"/>
• Variable for distinct values: <xsl:variable name="something" select="$objects//tei:rs[@type='something' and @subtype='something']/@ref" as="xs:string"/>

Then I add various elements for each distinct value to $objects: <xsl:for-each select="distinct-values($something)"/>

I tested the transformation before and it worked out fine. Now I'm getting the error message "The required item type of the first operand of '/' is node(); the supplied value xs:base64Binary("AAAAAUJ1ZDEAB ...=") is an atomic value."

How can I fix this problem? I've read quite a bit about this problem, but just can't get my stylesheet to work.

I'm using Saxon-PE 9.9.1.7 in Oxygen XML Editor. The stylesheet is written in XSLT 2.0.

Thank you in advance!

My guess would be that ../../../../data/objects is a directory containing a file that isn't recognizably XML, and is therefore being treated as a binary value. The rules Saxon applies for detecting the content type of the files in a collection are quite complex and a little arbitrary, but there are various ways you can restrict the selection to contain only XML files.