wonderful! This works! How can I ommit empty tags? They should not be
converted to attributes.

Throw in another template to suppress element nodes the string value of
which is the empty string:

Note this presupposes you do not have any child elements attached to the
element nodes matched by the above template, not to mention attributes
and other children. If, however, you do, then you must ensure processing
continues in the same mode by nesting:

    <xsl:apply-templates select="*" mode="attr"/>         or:
    <xsl:apply-templates select="node()|@*" mode="attr"/>