- From: Dave Singer <singer@apple.com>
- Date: Wed, 21 May 2008 08:34:53 -0700
- To: Bert Bos <bert@w3.org>, "www-style@w3.org" <www-style@w3.org>
At 23:39 +0200 20/05/08, Bert Bos wrote:
>Another question is if the the top-level should be "font/".
>Convincing the IETF to accept a new top-level type will be a long
>process. A name such as "application/eot" will no doubt be easier.
This question came up a log time ago on the timed text working group,
when we thought we also would need font mime types.
I wrote an internet draft to start the process, which, as Bert says,
was predicted to be long and complex. The residue of that draft is
at <https://datatracker.ietf.org/drafts/draft-singer-font-mime/>.
The text is below.
A while later the TTWG determined that this was not critical to
progress, and since it was predicted to be hard to pursue, I dropped
it. However, the history, and maybe even the text, might be helpful
here.
* * * * *
Internet Engineering Task Force
INTERNET-DRAFT D. Singer
draft-singer-font-mime-00.doc Apple Computer
G. Adams
XFSI
Oct 14 2004
Expires: Apr 14 2005
The Font Primary Content Type for
Multipurpose Internet Mail Extensions
IPR Notice
By submitting this Internet-Draft, I certify that any applicable patent
or other IPR claims of which I am aware have been disclosed, or will be
disclosed, and any of which I become aware will be disclosed, in
accordance with RFC 3668.
Status of This Memo
This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as Internet-
Drafts.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
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The list of current Internet-Drafts can be accessed at
http://www.ietf.org/1id-abstracts.html
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The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119.
Distribution of this document is unlimited.
D. Singer and G. Adams [Page 1]
Internet Draft draft-singer-font-mime-00.doc Oct 14 2004
Copyright Notice
Copyright (C) The Internet Society (2004). All Rights Reserved.
PostScript, OpenType, and TrueType are registered trademarks of Adobe
Systems. Inc., Microsoft Corp., and Apple Computer Inc.,
respectively.
Abstract
This document serves to register and document the top-level MIME type
for fonts, under which the representation formats for fonts may be
registered. It also registers some specific font types under that
top-level type.
1 Introduction
The process of setting type in computer systems and other forms of
text presentation systems uses fonts in order to provide visual
representations of the glyphs. Just as with images, for example,
there are a number of ways to represent the visual information of the
glyphs. Early formats often used bitmaps, as these could be
carefully tuned for maximum readability at a given size, and the
displays were often 1-bit deep only. More recently, outline fonts
have come into use: in these fonts, the outlines of the glyphs are
described, and the presentation system renders the outline in the
desired position and size.
This document defines a top-level MIME type "font" under which
differing representation formats of fonts may be registered (e.g. a
bitmap or outline format). It should be emphasized that, just as
under the "image" top-level type one does not find registration for,
for example, "The Night-watch" (by Rembrandt) but instead "JPEG" (an
image representation system), so, under "font" one will not find
"Courier" (the name of a popular font) but perhaps "BDF" (the name of
a commonly used bitmap font format).
Historically there has not been a registration of formats for fonts.
Currently there is only one font representation format registered in
MIME, and that is under the "application" top-level type. However,
the use of this top-level type is not ideal. First, the
"application" sub-tree is treated (correctly) with great caution with
respect to viruses and other active code. Secondly, the lack of a
top-level type means that there is no opportunity to have a common
set of optional attributes, such as are specified here. Third, fonts
have a unique set of licensing and usage restrictions, which makes it
worthwhile to identify this general category with a unique top-level
D. Singer and G. Adams [Page 2]
Internet Draft draft-singer-font-mime-00.doc Oct 14 2004
type.
2 Security Considerations
Fonts are interpreted data structures.
Fonts may contain 'hints' for the alignment of visual aspects of the
glyphs with the display, and these hints may appear to be active
code. However, they operate within the confines of the glyph outline
conversion system and have no access outside the font rendering
machinery.
Fonts can be, however, quite complex, and a maliciously designed
complex font could cause undue resource consumption (e.g. memory or
CPU cycles) on a machine interpreting it. This is the case for many
formats however. Indeed, fonts are sufficiently complex that most if
not all interpreters cannot be completely protected from malicious
fonts without undue performance penalties.
Fonts are often licensed and that license may place restrictions on
the transmission of all or part of the font. It is outside the scope
of this specification to mandate any particular behavior, but the
authors of MIME registrations under the 'font' top-level type SHOULD
at the very least also mention the licensing considerations for the
transmission of fonts.
3 Definition
3.1 Encoding
Unrecognized sub-types of "font" should be treated as
"application/octet-stream". Implementations may pass unrecognized
sub-types to a common font-handling system, if any.
Different subtypes of font may be encoded as textual representations
or as binary data. Unless noted in the subtype registration, subtypes
of font should be assumed to contain binary data, implying a content
encoding of base64 for email and binary transfer for ftp and http.
3.1 Common Parameters
The following two parameters may be supplied for any registration
under the "font" top-level type unless specifically disallowed by the
registration of that format.
It might be thought desirable to have a sub-parameter for the glyph
coverage of a font, but there is no known method that gives an
D. Singer and G. Adams [Page 3]
Internet Draft draft-singer-font-mime-00.doc Oct 14 2004
adequate summary of the coverage in an exact enough form to be
useful. This specification does not, therefore, define any such
parameter. However, the authors are investigating whether the
Unicode sets as defined at <
http://www.unicode.org/reports/tr35/#Unicode_Sets> could meet this
need.
These parameters are informative and typically duplicate information
found in the font itself. For interpreting the font file, the
information within the file is definitive and over-rides any of these
parameters. These parameters can be used to determine whether a font
can or should be opened, for example. The parameters SHOULD
correspond to what is in the file.
font-name="string"
This is the reference name for the font; a non-localized name that
is used to refer to it. In many fonts (even those not using
PostScript), this is the called "the postscript name". (e.g.
"Courier").
font-size="integer"
If a font is designed for use at a particular size (e.g. a bitmap
font), then this parameter is used to indicate the intended display
size. The value of the parameter is the nominal 'design size' of the
font, in pixels (e.g. a font designed for a nominal display size of
10 points on a display with 1 pixel per point would report the value
"10" here). This parameter is normally only used for fonts such as a
single-size bitmap font, designed for use at one size only.
subformat="string"
For font containers that allow multiple representations, and
therefore could require different font machinery, this identifies the
format needed, from an enumerated set defined in this specification
or specifications of specific formats under the "font/" node. This
specification defines "truetype" and "postscript" as possible values
for this parameter.
unicode="boolean"
The value of this parameter indicates whether the font supports a
mapping from Unicode scalar values or Unicode encoding form to
specific glyph(s); it takes the value "true" or "false".
4 Defined and Expected Sub-types
D. Singer and G. Adams [Page 4]
Internet Draft draft-singer-font-mime-00.doc Oct 14 2004
In this section the initial entries under the top-level 'font' MIME
type are documented. They also serve as examples for future
registrations.
Note that Macintosh operating systems are not particular about the
file-type code used for fonts, and that it is correct that the two
overlapping formats registered here use the same file type.
4.1 OpenType
The font/opentype content-type refers fonts that conform to the
OpenType specification. OpenType fonts are a special case of SFNT
fonts, which have a separate MIME type. The specific OpenType MIME
type is preferred when the fact that it is an OpenType font is
salient to the application or usage, and when the originating system
can reasonably determine that a font is a valid OpenType font.
To: ietf-types@iana.org
Subject: Registration of Standard MIME media type font/opentype
MIME media type name: font
MIME subtype name: opentype
Required parameters: none
Optional parameters: any of the common parameters for
'font' may be used, as documented in
RFC XXXX
Encoding considerations: files are binary and should be
transmitted in a suitable encoding
without CR/LF conversion, 7-bit
stripping etc.; base64 is a suitable
encoding;
Security considerations: see the security considerations
section in RFC XXXX
Interoperability considerations: OpenType fonts should ...
Published specification:
http://www.microsoft.com/typography/otspec/default.htm
Applications which use this media type: Messaging and multi-media
Additional information:
Magic number(s): no true magic number, but currently
files start with a 32-bit field,
which contains either 0x00010000 or
'OTTO'
File extension(s): "otf" is the common extension used;
"ttf" may be used for OpenType fonts
containing TrueType outlines, "ttc"
is used for TrueType Collections
fonts
Macintosh File Type Code(s): sfnt may be used but is not required
D. Singer and G. Adams [Page 5]
Internet Draft draft-singer-font-mime-00.doc Oct 14 2004
Person & email address to contact for further information:
???: ???@???.com
Intended usage: COMMON
Change controller: ???: ???@???.com
4.2 Sfnt
The font/sfnt content-type refers fonts that are contained within an
'sfnt' (scalable font) container, but that are not necessarily
OpenType. (OpenType fonts also use this container format, but there
is a substantial body of fonts using the container format that are
not OpenType fonts).
To: ietf-types@iana.org
Subject: Registration of Standard MIME media type font/sfnt
MIME media type name: font
MIME subtype name: sfnt
Required parameters: none
Optional parameters: any of the common parameters for
'font' may be used, as documented in
RFC XXXX
Encoding considerations: files are binary and should be
transmitted in a suitable encoding
without CR/LF conversion, 7-bit
stripping etc.; base64 is a suitable
encoding;
Security considerations: see the security considerations
section in RFC XXXX
Interoperability considerations: Sfnt fonts may contain a variety of
tables, some or all of which may be
vendor-specific or otherwise non-
standard. The SFNT structure does
not require any specific set of
tables, though there are tables in
common use. Interoperability is not
assured.
Published specification:
http://developer.apple.com/fonts/TTRefMan/
Applications which use this media type: Messaging and multi-media
Additional information:
Magic number(s): no true magic number, but currently
files start with a 32-bit field,
which contains either 0x00010000, or
'OTTO', or 'true' or 'typ1'
File extension(s): "ttf" is a common extension used, for
sfnt-housed TrueType fonts
D. Singer and G. Adams [Page 6]
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Macintosh File Type Code(s): sfnt may be used but is not required
Person & email address to contact for further information:
???: ???@???.com
Intended usage: COMMON
Change controller: ???: ???@???.com
5 IANA Considerations
This document registers the top-level MIME type "font", and the
"opentype" font type under "font".
6 RFC Editor Considerations
The references to RFC XXXX in the MIME registrations need to be
replaced with the actual RFC number when it is issued.
7 Full Copyright Statement
Copyright (C) The Internet Society (2004). This document is subject
to the rights, licenses and restrictions contained in BCP 78, and
except as set forth therein, the authors retain all their rights.
This document and the information contained herein are provided on an
"AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
8 Intellectual Property Notice
The IETF takes no position regarding the validity or scope of any
intellectual property or other rights that might be claimed to
pertain to the implementation or use of the technology described in
this document or the extent to which any license under such rights
might or might not be available; neither does it represent that it
has made any effort to identify any such rights. Information on the
IETF's procedures with respect to rights in standards-track and
standards-related documentation can be found in BCP-11. Copies of
claims of rights made available for publication and any assurances of
licenses to be made available, or the result of an attempt made to
obtain a general license or permission for the use of such
proprietary rights by implementers or users of this specification can
be obtained from the IETF Secretariat.
D. Singer and G. Adams [Page 7]
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The IETF invites any interested party to bring to its attention any
copyrights, patents or patent applications, or other proprietary
rights which may cover technology that may be required to practice
this standard. Please address the information to the IETF Executive
Director.
Acknowledgments
The initial review by the W3C Timed Text group, and type experts, is
gratefully acknowledged.
D. Singer and G. Adams [Page 8]
Internet Draft draft-singer-font-mime-00.doc Oct 14 2004
Authors' Contact Information
David Singer
Apple Computer, Inc.
One Infinite Loop, MS:302-3MT
Cupertino CA 95014
USA
Email: singer@apple.com
Tel: +1 408 974 3162
Glenn Adams
Extensible Formatting Systems, Inc. (XFSI)
114 Mount Auburn St, 4th Floor
Cambridge, MA 02138
USA
Tel: +1 617 864-0005
Fax: +1 617 864-0006
Email: gadams@xfsi.com
6. References
[ISO-JPEG2000-1]
ITU-T Recommendation T.800 | ISO/IEC 15444-1. International
Organization for Standardization, "JPEG 2000 Image Coding System:
Core Coding System".
[MIME1] Freed, N. and N. Borenstein, "Multipurpose Internet Mail
Extensions (MIME) Part One: Format of Internet Message Bodies", RFC
2045, November 1996.
Dates
Written: Oct 14 2004
Expires: Apr 14 2005
D. Singer and G. Adams [Page 9]
--
David Singer
Apple/QuickTime
Received on Wednesday, 21 May 2008 15:37:19 UTC