\startbuffer[test]
<something whatever="alpha #">
    <what>
        test #
    </what>
</something>
\stopbuffer

\startxmlsetups xml:mysetups
    \xmlsetsetup{\xmldocument}{something}{xml:*}
\stopxmlsetups

\xmlregistersetup{xml:mysetups}

\startxmlsetups xml:something
    \xmlatt{#1}{whatever}
    \xmlfirst{#1}{what}
\stopxmlsetups

\starttext
    \xmlprocessbuffer{main}{test}{}
\stoptext
