I have two kinds of reservations about this:
1. indicating any copyright information in the headers of a body part
2. using content-disposition for this purpose
Copyright is by itself a problematic issue. Many people (including
myself) believing that traditional notions of copyright are obsolete and
harmful when applied to the networked world.
It's not immediately clear how the information would be used by the
recipient. In countries that have signed the Berne convention,
essentially everything is copyrighted anyway. And yet the very actions
of transmitting a message over email, reading the message from a message
store using POP or IMAP, and using attachments (e.g. providing a copy of
"just the attachment" in a file where it can be used by a helper
application) requires making several copies of the message.
Furthermore, to be effective any kind of limitation on the use of the
attachment would need to be communicated to any helper application (so
that, for instance, "save" or "print" functions could be disabled or
limited). In this context it seems clear that (if the sender has the
right to do so) some permission to copy is being granted by the
sender to the recipient and to various intermediaries, or (if the
sender does not have that right) that the sender is violating one or
more rights held by the content owner.
Also, copyright laws are particular about what kinds of marks are
suitable for legally serving as copyright notice, and it's not clear
that a new content-disposition field, or a new body-part header field,
would meet the requirements of such laws - particularly when the notice
would in some sense be separated from the actual copyrighted work.
So I believe that copyright notices in the message header would be at
best ambigious and ineffective, and at worst confusing and detrimental.
Whether to use the Content-Disposition field for this purpose is a
separate issue. Content-Disposition is intended to be used by the
sender to make recommendations as to how the recipient (or the
recipient's mail user agent) should deal with the document. It's not
clear that copyright information falls into that category, because
the very notion of copyright is ambiguous in an environment where there
is no obvious distinction between copying and ordinary use.
The entire body-part header (rather than one particular field) exists to
describe the body-part, and the purist in me would like to keep each
field of that header (includingcontent-disposition) true to its purpose,
so that there is a clean separation of function between the different
fields. For instance, it might be found desirable to display copyright
information to the recipient (so that he or she can be expected to act
in awareness of that notice). But content-disposition fields are not
So _if_ it were found to be desirable to include copyright information
in the MIME body part header, I believe it should be in a separate field
Regime change 2004 - better late than never.