RFC 2397, "The "data" URL scheme", August 1998

Errata ID: 3214
Status: Held for Document Update
Type: Technical
Publication Format(s) : TEXT
Reported By: Julian Reschke
Date Reported: 2012-05-06
Held for Document Update by: Barry Leiba

Section 3 says:

   Attribute values in [RFC2045] are allowed to be either represented as
   tokens or as quoted strings. However, within a "data" URL, the
   "quoted-string" representation would be awkward, since the quote mark
   is itself not a valid urlchar. For this reason, parameter values
   should use the URL Escaped encoding instead of quoted string if the
   parameter values contain any "tspecial".

Notes:

This advice does not work when the character is a delimiter such as ";".

Example media type:

text/plain;foo="bar;charset=iso-8859-1";charset=UTF-8

...represented as-is in data uri:

data:text/plain;foo=%22bar;charset=iso-8859-1%22;charset=UTF-8,...

...but following the advice from Section 3:

data:text/plain;foo=bar;charset=iso-8859-1;charset=UTF-8,...

which makes the charset parameter ambiguous.

Proposal for document update:

1) Keep the text pointing out double quotes will look awkward.

2) Insist on them being handled as per RFC 2045, when present.

3) Either remove the last sentence (after checking whether it's done in practice), or clarify which additional non-token characters are allowed here.

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