RFC 2183 (rfc2183) - Page 2 of 12
Communicating Presentation Information in Internet Messages: The Content-Disposition Header Field
Alternative Format: Original Text Document
RFC 2183 Content-Disposition August 1997
1. Introduction
MIME specifies a standard format for encapsulating multiple pieces of
data into a single Internet message. That document does not address
the issue of presentation styles; it provides a framework for the
interchange of message content, but leaves presentation issues solely
in the hands of mail user agent (MUA) implementors.
Two common ways of presenting multipart electronic messages are as a
main document with a list of separate attachments, and as a single
document with the various parts expanded (displayed) inline. The
display of an attachment is generally construed to require positive
action on the part of the recipient, while inline message components
are displayed automatically when the message is viewed. A mechanism
is needed to allow the sender to transmit this sort of presentational
information to the recipient; the Content-Disposition header provides
this mechanism, allowing each component of a message to be tagged
with an indication of its desired presentation semantics.
Tagging messages in this manner will often be sufficient for basic
message formatting. However, in many cases a more powerful and
flexible approach will be necessary. The definition of such
approaches is beyond the scope of this memo; however, such approaches
can benefit from additional Content-Disposition values and
parameters, to be defined at a later date.
In addition to allowing the sender to specify the presentational
disposition of a message component, it is desirable to allow her to
indicate a default archival disposition; a filename. The optional
"filename" parameter provides for this. Further, the creation-date,
modification-date, and read-date parameters allow preservation of
those file attributes when the file is transmitted over MIME email.
NB: The keywords MUST, MUST NOT, REQUIRED, SHALL, SHALL NOT, SHOULD,
SHOULD NOT, RECOMMENDED, MAY, and OPTIONAL, when they appear in this
document, are to be interpreted as described in [RFC 2119].
2. The Content-Disposition Header Field
Content-Disposition is an optional header field. In its absence, the
MUA may use whatever presentation method it deems suitable.
It is desirable to keep the set of possible disposition types small
and well defined, to avoid needless complexity. Even so, evolving
usage will likely require the definition of additional disposition
types or parameters, so the set of disposition values is extensible;
see below.
Troost, et. al. Standards Track