W3C home > Mailing lists > Public > www-style@w3.org > May 2008

Re: Font MIME types

From: Dave Singer <singer@apple.com>
Date: Wed, 21 May 2008 08:34:53 -0700
Message-Id: <p0624082bc459eff98bb8@[17.202.35.52]>
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
    material or to cite them other than a "work in progress."

    The list of current Internet-Drafts can be accessed at
    http://www.ietf.org/1id-abstracts.html

    The list of Internet-Draft Shadow Directories can be accessed at
    http://www.ietf.org/shadow.html

    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]





Internet Draft        draft-singer-font-mime-00.doc        Oct 14 2004


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]





Internet Draft        draft-singer-font-mime-00.doc        Oct 14 2004


    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 GMT

This archive was generated by hypermail 2.2.0+W3C-0.50 : Monday, 27 April 2009 13:55:06 GMT