xml - Open/unrestricted attribute list for an element in a DTD? -

is possible, within dtd, define element have open/unrestricted attribute list?

i know can defined element have unrestricted child elements:

<!element element_name any> 

but, tutorials , references have consulted seem assume attribute list element must complete. , couldn't find explicit reference situation.

not if wish validate it. (zvon gives overview of dtd): http://zvon.org/xxl/dtdtutorial/general/contents.html. if not use validator well-formed xml allowed.

in xsd schema possible allow undeclared attributes including other namespaces (namespaces difficult manage in dtds).