This is just Scheme. It's nothing to do with SXML. #:foo is a keyword argument and '(apache httpd) is a quoted list containing the symbols apache and httpd.

This is just Scheme. It's nothing to do with SXML. #:foo is a keyword argument and '(apache httpd) is a quoted list containing the symbols apache and httpd. Angled brackets have no special meaning, they are just part of the identifier.