This element contains the name of the
attachment (please limit to 256 char) along with the mime-type attribute which
identifies the content type using the MIME media type values found in RFC 2046.
An ITS Client may originate any attachment type defined within the
specification. A minimum set of file types should be recognized by a consuming
ITS Client. This minimum set is also the only file types allowed to cross a
security domain. Within a single security domain other files types are allowed
as long as the originating Client and receiving Client are in agreement on the
handling of the attachment.