RFC 2183 (rfc2183) - Page 2 of 12

Communicating Presentation Information in Internet Messages: The Content-Disposition Header Field

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