RFC 1806 (rfc1806) - Page 2 of 8
Communicating Presentation Information in Internet Messages: The Content-Disposition Header
Alternative Format: Original Text Document
RFC 1806 Content-Disposition June 1995
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.
2. The Content-Disposition Header Field
Content-Disposition is an optional header; 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.
In the extended BNF notation of [RFC 822], the Content-Disposition
header field is defined as follows:
disposition := "Content-Disposition" ":"
disposition-type
*(";" disposition-parm)
disposition-type := "inline"
/ "attachment"
/ extension-token
; values are not case-sensitive
disposition-parm := filename-parm / parameter
filename-parm := "filename" "=" value;
`Extension-token', `parameter' and `value' are defined according to
[RFC 822] and [RFC 1521].
Troost & Dorner Experimental