[NTG-context] \xmlstrip?

I encounter difficulties in stripping the leading and trailing whitespace from a node. The following does not work for me, typesetting \CAST delivers an empty result: \def\Cast#1{\def\CAST{#1}} \startxmlsetups xml:case:cast \Cast{\xmlstrip{#1}{}} \stopxmlsetups nor do variants like: \Cast{xmlstrip{#1}{*}} \Cast{xmlstrip{#1}{/}} \Cast{xmlstrip{#1}{/cast}} What does work is: \Cast{\xmlflush{#1}} How do I proceed? Hans van der Meer