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Versions: 00 01 02 03 04 05 06 RFC 8081

Network Working Group                                          C. Lilley
Internet-Draft                                                       W3C
Intended status: Standards Track                       November 15, 2016
Expires: May 19, 2017


                        The font Top Level Type
                    draft-ietf-justfont-toplevel-04

Abstract

   This memo serves to register and document the "font" Top Level Type,
   under which the Internet Media subtypes for representation formats
   for fonts may be registered.  This document also serves as a
   registration application for a set of intended subtypes, which are
   representative of some existing subtypes already in use, and
   currently registered under the "application" tree by their separate
   registrations.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   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 as "work in progress."

   This Internet-Draft will expire on May 19, 2017.

Copyright Notice

   Copyright (c) 2016 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of



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   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

1.  Specification Development

   [Note to the RFC Editor: Please remove this section upon
   publication.]

   This section is non-normative.  The source for this specification is
   maintained on GitHub [1].  The issues list [2] is also on GitHub.
   Discussion should be on the mailing list justfont@ietf.org [3].

2.  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 font formats often used bitmaps, as these could have
   been carefully tuned for maximum readability at a given size on low-
   resolution displays.  More recently, scalable vector outline fonts
   have come into widespread use: in these fonts, the outlines of the
   glyphs are described, and the presentation system renders the outline
   in the desired position and size.

   Over time, a number of standard formats for recording font
   descriptions have evolved.  This document defines a new top-level
   Internet Media Type "font" according to Section 4.2.7 of [RFC6838].
   This top-level type indicates that the content specifies font data.
   Under this top-level type, different representation formats of fonts
   may be registered.

   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 [RFC2119].

3.  Background and Justification

   Historically there has not been a registration of formats for fonts.
   More recently, there have been several representation formats
   registered as media subtypes under the "application" top-level type
   (for example, application/font-woff).  However, with the rapid
   adoption of web fonts (based on the data from HTTP Archive
   [HTTP-Archive-Trends] showing a huge increase in web font usage from
   1% in the end of 2010 to 50% across all sites in the beginning of
   2015) custom fonts on the web have become a core web resource.  As
   the in-depth analysis [Font-Media-Type-Analysis] shows, the lack of
   the intuitive top-level font type is causing significant confusion



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   among developers - while currently defined font subtypes are severely
   under-utilized there are many more sites that already use non-
   existent (but highly intuitive) media types such as "font/woff",
   "font/ttf" and "font/truetype".  At the same time, the majority of
   sites resort to using generic types such as "application/octet-
   stream", "text/plain" and "text/html"; or use unregistrable types
   such as "application/x-font-ttf".

   Contrary to the expectations of the W3C WebFonts Working Group which
   developed WOFF, the officially defined IANA subtypes such as
   "application/font-woff" and "application/font-sfnt" see a very
   limited use - their adoption rates trail far behind as the actual use
   of web fonts continues to increase.  The members of the W3C WebFonts
   WG concluded that the use of "application" 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 parameters, 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 type.

   The W3C WebFonts WG decided [WG-tlt] that the situation can be
   significantly improved if a set of font media types is registered
   using "font" as a dedicated top-level type.  Based on the data
   analysis presented above, we conclude that it is the presence of
   simple and highly intuitive media types for images that caused their
   widespread adoption, where the correct usage of existing media types
   reaches over 97% for all subtypes in the "image" tree.  The WG
   considers that, considering a rapid adoption of fonts on the web, the
   registration of the top-level media type for fonts along with the
   intuitive set of subtypes that reflect popular and widely used data
   formats would further stimulate the adoption of web fonts,
   significantly simplify web server configuration process and
   facilitate the proper use of IANA media type recommendations.

4.  Security Considerations

   Fonts are interpreted data structures that represent collections of
   different tables containing data that represent different types of
   information, including glyph outlines in various formats, hinting
   instructions, metrics and layout information for multiple languages
   and writing systems, rules for glyph substitution and positioning,
   etc.  In particular, the hinting instructions for TrueType glyphs
   represent executable code which has the potential to be maliciously
   constructed (for example, intended to hang the interpreter).  There
   are many existing, already standardized font table tags and formats
   that allow an unspecified number of entries containing predefined



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   data fields for storage of variable length binary data.  Many
   existing font formats (TrueType [truetype-wiki], OpenType and OFF
   [opentype-wiki], SIL Graphite, WOFF, etc.) are based on the table-
   based SFNT (scalable font) format which is extremely flexible, highly
   extensible and offers an opportunity to introduce additional table
   structures when needed, in an upward-compatible way that would not
   affect existing font rendering engines and text layout
   implementations.  However, this very extensibility may present
   specific security concerns - the flexibility and ease of adding new
   data structures makes it easy for any arbitrary data to be hidden
   inside a font file.  There is a significant risk that the flexibility
   of font data structures may be exploited to hide malicious binary
   content disguised as a font data component.

   Fonts may contain 'hints', which are programmatic instructions that
   are executed by the font engine for the alignment of graphical
   elements of glyph outlines with the target display pixel grid.
   Depending on the font technology utilized in the creation of a font
   these hints may represent active code interpreted and executed by the
   font rasterizer.  Even though hints operate within the confines of
   the glyph outline conversion system and have no access outside the
   font rendering engine, hint instructions 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.  Indeed, fonts are sufficiently complex that most
   (if not all) interpreters cannot be completely protected from
   malicious fonts without undue performance penalties.

   Widespread use of fonts as necessary components of visual content
   presentation warrants that careful attention should be given to
   security considerations whenever a font is either embedded into an
   electronic document or transmitted alongside media content as a
   linked resource.  While many existing font formats provide certain
   levels of protection of data integrity (such mechanisms include e.g.
   checksums and digital signatures), font data formats provide neither
   privacy nor confidentiality protection internally; if needed, such
   protection should be provided externally.

5.  IANA Considerations

   This specification registers a new top-level type, "font", in the
   standards tree; adds it as an alternative value of "Type Name" in the
   media types registration form [Media-Type-Registration]; and
   registers several subtypes for it.







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5.1.  Definition and Encoding

   The "font" as the primary media content type indicates that the
   content identified by it requires certain graphic subsystem such as
   font rendering engine (and, in some cases, text layout and shaping
   engine) to process it as font data, which in turn may require certain
   level of hardware capabilities such as certain levels of CPU
   performance and available memory.  The "font" media type does not
   provide any specific information about the underlying data format and
   how the font information should be interpreted - the subtypes defined
   within a "font" tree name the specific font formats.  Unrecognized
   sub-types of "font" should be treated as "application/octet-stream".
   Implementations may pass unrecognized subtypes to a common font-
   handling system, if such a system is available.

5.2.  Registration Procedure

   New font formats should be registered using the online form
   [Media-Type-Registration].  RFC 6838 [RFC6838] should be consulted on
   registration procedures.  In particular the font specification must
   be freely available.  Also, an @font-face format should be supplied
   and, if used, a definition of the fragment identifier syntax for the
   new type.

   Note that new parameter sub-values may be defined in the future.  If
   an implementation does not recognize a sub-value in the comma-
   separated list, it should ignore the sub-value and continue
   processing the other sub-values in the list.

5.3.  Subtype Registrations

   In this section the initial entries under the top-level 'font' media
   type are specified.  They also serve as examples for future
   registrations.

   For each subtype, an @font-face format identifer is defined.  This is
   for use with the @font-face src descriptor, defined by the CSS3 Fonts
   specification [W3C.CR-css-fonts-3-20131003].

5.3.1.  Generic SFNT Font Type

   Type name:  font

   Subtype name:  sfnt

   Required parameters:  None.

   Optional parameters:



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      1) Name: outlines  Value: TTF, CFF, SVG

         This parameter can be used to specify the type of outlines
         provided by the font.  Value "TTF" shall be used when a font
         resource contains glyph outlines in TrueType format, value
         "CFF" shall be used to identify fonts containing PostScript/CFF
         outlines [cff-wiki], and value SVG [svg-wiki]shall be used to
         identify fonts that include SVG outlines.  TTF, CFF or SVG
         outlines can be present in various combinations in the same
         font file, therefore, this optional parameter is a list
         containing one or more items, separated by commas, with
         optional whitespace.  Order in the list is not significant.

      2) Name: layout

         Value: OTL, AAT, SIL

         This parameter identifies the type of implemented support for
         advanced text layout features.  The predefined values "OTL",
         "AAT" and "SIL" respectively indicate support for OpenType text
         layout, Apple Advanced Typography or Graphite SIL.  More than
         one shaping and layout mechanism may be provided by the same
         font file, therefore, this optional parameter is a list
         containing one or more items, separated by commas, with
         optional whitespace.  Order in the list is not significant.

   Encoding considerations:  Binary.

   Interoperability considerations:  As it was noted in the first
      paragraph of the "Security considerations" section, a single font
      file can contain encoding of the same glyphs using several
      different representations, e.g., both TrueType and PostScript
      (CFF) outlines.  Existing font rendering engines may not be able
      to process some of the particular outline formats, and downloading
      a font resource that contains only unsupported glyph data format
      would be futile.  Therefore, it is useful to clearly identify the
      format of the glyph outline data within a font using an optional
      parameter, and allow applications to make decisions about
      downloading a particular font resource sooner.  Similarly, another
      optional parameter identifies the type of text shaping and layout
      mechanism that is provided by a font.

   Published specification:  ISO/IEC 14496-22 "Open Font Format" (OFF)
      specification [ISO.14496-22.2015] being developed by ISO/IEC SC29/
      WG11.

   Applications that use this media type:  All applications that are
      able to create, edit or display textual media content.



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   Additional information:

      Magic number(s):  The TrueType fonts and OFF / OpenType fonts
         containing TrueType outlines should use 0x00010000 as the
         'sfnt' version number.

         The OFF / OpenType fonts containing CFF data should use the tag
         'OTTO' as 'sfnt' version number.

      File extension(s):  Font file extensions used for OFF / OpenType
         fonts: .ttf, .otf

         Typically, .ttf extension is only used for fonts containing
         TrueType outlines, while .otf extension can be used for any
         OpenType/OFF font, either with TrueType or CFF outlines.

      Macintosh file type code(s):  (no code specified)

      @font-face Format:  none.

      Fragment Identifiers  none.

      Deprecated Alias:  The existing registration application/font-sfnt
         is deprecated in favor of font/sfnt.

   Person & email address to contact for further information:  Vladimir
      Levantovsky (vladimir.levantovsky@monotype.com).

   Intended usage:  COMMON

   Restrictions on usage:  None

   Author:  The ISO/IEC 14496-22 "Open Font Format" specification is a
      product of the ISO/IEC JTC1 SC29/WG11.

   Change controller:  The ISO/IEC has change control over this
      specification.

5.3.2.  TTF Font Type

   Type name:  font

   Subtype name:  ttf

   Required parameters:  None.

   Optional parameters:




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      Name: layout  Value: OTL, AAT, SIL

         This parameter identifies the type of support mechanism for
         advanced text layout features.  The predefined values "OTL",
         "AAT" and "SIL" respectively indicate support for OpenType text
         layout, Apple Advanced Typography or Graphite SIL.  More than
         one shaping and layout mechanism may be provided by the same
         font file, therefore, this optional parameter is a list
         containing one or more items, separated by commas, with
         optional whitespace.  Order in the list is not significant.

   Encoding considerations:  Binary.

   Interoperability considerations:  As it was noted in the first
      paragraph of the "Security considerations" section, a single font
      file can contain encoding of the same glyphs using several
      different representations, e.g., both TrueType and PostScript
      (CFF) outlines.  Existing font rendering engines may not be able
      to process some of the particular outline formats, and downloading
      a font resource that contains only unsupported glyph data format
      would be futile.  Therefore, it is useful to clearly identify the
      format of the glyph outline data within a font using an optional
      parameter, and allow applications to make decisions about
      downloading a particular font resource sooner.  Similarly, another
      optional parameter identifies the type of text shaping and layout
      mechanism that is provided by a font.

   Published specification:  ISO/IEC 14496-22 "Open Font Format" (OFF)
      specification [ISO.14496-22.2015] being developed by ISO/IEC SC29/
      WG11.

   Applications that use this media type:  All applications that are
      able to create, edit or display textual media content.

   Additional information:

      Magic number(s):  The TrueType fonts and OFF / OpenType fonts
         containing TrueType outlines should use 0x00010000 as the
         'sfnt' version number.

      File extension(s):  Font file extensions used for TrueType / OFF /
         OpenType fonts: .ttf, .otf

         Typically, .ttf extension is only used for fonts containing
         TrueType outlines, while .otf extension may be used for any
         OpenType/OFF font, either with TrueType or CFF outlines.

      Macintosh file type code(s):  (no code specified)



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      @font-face Format:  truetype

      Fragment Identifiers  none.

   Person & email address to contact for further information:  Vladimir
      Levantovsky (vladimir.levantovsky@monotype.com).

   Intended usage:  COMMON

   Restrictions on usage:  None

   Author:  The ISO/IEC 14496-22 "Open Font Format" specification is a
      product of the ISO/IEC JTC1 SC29/WG11.

   Change controller:  The ISO/IEC has change control over this
      specification.

5.3.3.  OTF Font Type

   Type name:  font

   Subtype name:  otf

   Required parameters:  None.

   Optional parameters

      Name: outlines  Value: TTF, CFF, SVG

         This parameter can be used to specify the type of outlines
         provided by the font.  Value "TTF" shall be used when a font
         resource contains glyph outlines in TrueType format, value
         "CFF" shall be used to identify fonts containing PostScript/CFF
         outlines, and value SVG shall be used to identify fonts that
         include SVG outlines.  TTF, CFF or SVG outlines can be present
         in various combinations in the same font file, therefore, this
         optional parameter is a list containing one or more items,
         separated by commas, with optional whitespace.  Order in the
         list is not significant.

   Encoding considerations:  Binary.

   Interoperability considerations:  As it was noted in the first
      paragraph of the "Security considerations" section, a single font
      file can contain encoding of the same glyphs using several
      different representations, e.g., both TrueType and PostScript
      (CFF) outlines.  Existing font rendering engines may not be able
      to process some of the particular outline formats, and downloading



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      a font resource that contains only unsupported glyph data format
      would be futile.  Therefore, it is useful to clearly identify the
      format of the glyph outline data within a font using an optional
      parameter, and allow applications to make decisions about
      downloading a particular font resource sooner.  Similarly, another
      optional parameter identifies the type of text shaping and layout
      mechanism that is provided by a font.

   Published specification:  ISO/IEC 14496-22 "Open Font Format" (OFF)
      specification [ISO.14496-22.2015] being developed by ISO/IEC SC29/
      WG11.

   Applications that use this media type:  All applications that are
      able to create, edit or display textual media content.

   Additional information:

      Magic number(s):  The TrueType fonts and OFF / OpenType fonts
         containing TrueType outlines should use 0x00010000 as the
         'sfnt' version number.

         The OFF / OpenType fonts containing CFF outlines should use the
         tag 'OTTO' as 'sfnt' version number.  There is no magic number
         for SVG outlines; these are always accompanied by either
         TrueType or CFF outlines and thus use the corresponding magic
         number.

      File extension(s):  Font file extensions used for OFF / OpenType
         fonts: .ttf, .otf

         Typically, .ttf extension is only used for fonts containing
         TrueType outlines, while .otf extension can be used for any
         OpenType/OFF font, either with TrueType, CFF or SVG outlines.

      Macintosh file type code(s):  (no code specified)

      @font-face Format:  opentype

      Fragment Identifiers  none.

   Person & email address to contact for further information:  Vladimir
      Levantovsky (vladimir.levantovsky@monotype.com).

   Intended usage:  COMMON

   Restrictions on usage:  None





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   Author:  The ISO/IEC 14496-22 "Open Font Format" specification is a
      product of the ISO/IEC JTC1 SC29/WG11.

   Change controller:  The ISO/IEC has change control over this
      specification.

5.3.4.  Collection Font Type

   Type name:  font

   Subtype name:  collection

   Required parameters:  None.

   Optional parameters

      Name: outlines  Value: TTF, CFF, SVG

         This parameter can be used to specify the type of outlines
         provided by the font.  Value "TTF" shall be used when a font
         resource contains glyph outlines in TrueType format, value
         "CFF" shall be used to identify fonts containing PostScript/CFF
         outlines, and value SVG shall be used to identify fonts that
         include SVG outlines.  TTF, CFF or SVG outlines can be present
         in various combinations in the same font file, therefore, this
         optional parameter is a list containing one or more items,
         separated by commas, with optional whitespace.  Order in the
         list is not significant.

   Encoding considerations:  Binary.

   Interoperability considerations:  As it was noted in the first
      paragraph of the "Security considerations" section, a single font
      file can contain encoding of the same glyphs using several
      different representations, e.g., both TrueType and PostScript
      (CFF) outlines.  Existing font rendering engines may not be able
      to process some of the particular outline formats, and downloading
      a font resource that contains only unsupported glyph data format
      would be futile.  Therefore, it is useful to clearly identify the
      format of the glyph outline data within a font using an optional
      parameter, and allow applications to make decisions about
      downloading a particular font resource sooner.  Similarly, another
      optional parameter identifies the type of text shaping and layout
      mechanism that is provided by a font.

   Published specification:  ISO/IEC 14496-22 "Open Font Format" (OFF)
      specification [ISO.14496-22.2015] being developed by ISO/IEC SC29/
      WG11.



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   Applications that use this media type:  All applications that are
      able to create, edit or display textual media content.

   Additional information:

      Magic number(s):  The TrueType fonts and OFF / OpenType fonts
         containing TrueType outlines should use 0x00010000 as the
         'sfnt' version number.

         The OFF / OpenType fonts containing CFF outlines should use the
         tag 'OTTO' as 'sfnt' version number.  There is no magic number
         for SVG outlines; these are always accompanied by either
         TrueType or CFF outlines and thus use the corresponding magic
         number.

      File extension(s):  Font file extensions used for OFF / TrueType
         and OpenType fonts: .ttc

      Macintosh file type code(s):  (no code specified)

      @font-face Format:  collection

      Fragment Identifiers  A positive integer.  For example, #2 refers
         to the second font in the collection.  If a fragment is not
         specified, it is the same as #1 i.e. the first font in the
         collection.

   Person & email address to contact for further information:  Vladimir
      Levantovsky (vladimir.levantovsky@monotype.com).

   Intended usage:  COMMON

   Restrictions on usage:  None

   Author:  The ISO/IEC 14496-22 "Open Font Format" specification is a
      product of the ISO/IEC JTC1 SC29/WG11.

   Change controller:  The ISO/IEC has change control over this
      specification.

5.3.5.  WOFF 1.0

   Type name:  font

   Subtype name:  woff

   Required parameters:  None.




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   Optional parameters:  None.

   Encoding considerations:  Binary.

   Interoperability considerations:  None.

   Published specification:  This media type registration updates the
      WOFF specification [W3C.REC-WOFF-20121213] at W3C.

   Applications that use this media type:  WOFF is used by Web browsers,
      often in conjunction with HTML and CSS.

   Additional information:

      Magic number(s):  The signature field in the WOFF header MUST
         contain the "magic number" 0x774F4646 ('wOFF')

      File extension(s):  woff

      Macintosh file type code(s):  (no code specified)

      Macintosh Universal Type Identifier code:  "org.w3c.woff"

      @font-face Format:  woff

      Fragment Identifiers:  none.

      Deprecated Alias:  The existing registration application/font-woff
         is deprecated in favor of font/woff.

   Person & email address to contact for further information:  Chris
      Lilley (www-font@w3.org).

   Intended usage:  COMMON

   Restrictions on usage:  None

   Author:  The WOFF specification is a work product of the World Wide
      Web Consortium's WebFonts Working Group.

   Change controller:  The W3C has change control over this
      specification.

5.3.6.  WOFF 2.0

   Type name:  font

   Subtype name:  woff2



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   Required parameters:  None.

   Optional parameters:  None.

   Encoding considerations:  Binary.

   Interoperability considerations:  WOFF 2.0 is an improvement on WOFF
      1.0.  The two formats have different Internet Media Types,
      different @font-face formats, and may be used in parallel.

   Published specification:  This media type registration is extracted
      from the WOFF 2.0 specification [W3C.WD-WOFF2-20150414] at W3C.

   Applications that use this media type:  WOFF 2.0 is used by Web
      browsers, often in conjunction with HTML and CSS.

   Additional information:

      Magic number(s):  The signature field in the WOFF header MUST
         contain the "magic number" 0x774F4632 ('wOF2')

      File extension(s):  woff2

      Macintosh file type code(s):  (no code specified)

      Macintosh Universal Type Identifier code:  "org.w3c.woff2"

      @font-face Format:  woff2

      Fragment Identifiers  If the WOFF is not a collection, the only
         fragment identifier is "1", which specifies the only font
         contained in the object.  If the WOFF is a collection, an
         integer (1-origin) specifying a font contained in the
         collection.

   Person & email address to contact for further information:  Chris
      Lilley (www-font@w3.org).

   Intended usage:  COMMON

   Restrictions on usage:  None

   Author:  The WOFF2 specification is a work product of the World Wide
      Web Consortium's WebFonts Working Group.

   Change controller:  The W3C has change control over this
      specification.




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6.  References

6.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <http://www.rfc-editor.org/info/rfc2119>.

   [RFC6838]  Freed, N., Klensin, J., and T. Hansen, "Media Type
              Specifications and Registration Procedures", BCP 13,
              RFC 6838, DOI 10.17487/RFC6838, January 2013,
              <http://www.rfc-editor.org/info/rfc6838>.

   [W3C.CR-css-fonts-3-20131003]
              Daggett, J., "CSS Fonts Module Level 3", World Wide Web
              Consortium CR CR-css-fonts-3-20131003, October 2013,
              <http://www.w3.org/TR/2013/CR-css-fonts-3-20131003>.

   [ISO.14496-22.2015]
              International Organization for Standardization, "Coding of
              audio-visual objects Part 22: Open Font Format",
              ISO Standard 14496-22, 10 2015,
              <http://standards.iso.org/ittf/PubliclyAvailableStandards/
              c066391_ISO_IEC_14496-22_2015.zip>.

   [W3C.REC-WOFF-20121213]
              Kew, J., Leming, T., and E. Blokland, "WOFF File Format
              1.0", World Wide Web Consortium Recommendation REC-WOFF-
              20121213, December 2012,
              <http://www.w3.org/TR/2012/REC-WOFF-20121213>.

   [W3C.WD-WOFF2-20150414]
              Levantovsky, V. and R. Levien, "WOFF File Format 2.0",
              World Wide Web Consortium WD WD-WOFF2-20150414, March
              2016, <https://www.w3.org/TR/2016/CR-WOFF2-20160315/>.

6.2.  Informative References

   [cff-wiki]
              "CFF", <https://en.wikipedia.org/wiki/
              PostScript_fonts#Compact_Font_Format>.

   [opentype-wiki]
              "OpenType", <https://en.wikipedia.org/wiki/OpenType>.

   [truetype-wiki]
              "TrueType", <https://en.wikipedia.org/wiki/TrueType>.



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   [svg-wiki]
              "SVG", <https://en.wikipedia.org/wiki/
              Scalable_Vector_Graphics>.

   [HTTP-Archive-Trends]
              Kuetell, D., "HTTP Archive trend analysis", March 2015,
              <http://httparchive.org/trends.php?s=All&minlabel=Nov+15+2
              010&maxlabel=Feb+15+2015#perFonts>.

   [Font-Media-Type-Analysis]
              Kuetell, D., "Web Font Media Type (mime type) Analysis
              2015", 2015, <http://goo.gl/zbDhUN>.

   [WG-tlt]   W3C, "ACTION-164: Bring widely used top-level-type to w3c-
              ietf liaison", 2015, <https://www.w3.org/Fonts/WG/track/
              actions/164>.

   [Media-Type-Registration]
              IANA, "Application for a Media Type",
              <http://www.iana.org/form/media-types>.

6.3.  URIs

   [1] https://github.com/svgeesus/ietf-justfont

   [2] https://github.com/svgeesus/ietf-justfont/issues

   [3] mailto:justfont@ietf.org

Author's Address

   Chris Lilley
   W3C
   2004 Route des Lucioles
   Sophia Antipolis  06902
   France

   Email: chris@w3.org













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