I am the assigned Gen-ART reviewer for this draft. The General Area Review Team (Gen-ART) reviews all IETF documents being processed by the IESG for the IETF Chair. Please treat these comments just like any other last call comments. For more information, please see the FAQ at <http://wiki.tools.ietf.org/area/gen/trac/wiki/GenArtfaq>. Document: draft-ietf-justfont-toplevel-03 Reviewer: Dale R. Worley Review Date: 2016-10-30 IETF LC End Date: 2016-11-09 IESG Telechat date: "Not yet" Summary: This draft is on the right track but has open issues, described in the review. These issues are editorial, except: whether the types font/ttf, font/otf, and font/collection are just subsets of font/sntf allowing whitespace in parameter values whether these type names should be deprecated: application/x-font-ttf application/font-sfnt application/vns.ms-fontobject -- The current RFC Editor preference seems to be that section titles should capitalize the first and "important" words. Some of the section titles adhere to this format but the following ones do not: 1. Specification development 4. Security considerations 6. Definition and encoding 7. Defined subtypes 7.1. Generic SFNT font type 7.2. TTF font type 7.3. OTF font type 7.4. Collection font type 1. Specification development If this section is only relevant to the Internet-Draft, this section should have a note to the RFC Editor to remove it upon publication. If it is intended for ongoing development after the Internet-Draft becomes an RFC, the wording should be revised since, e.g., once an RFC is published, it is fixed, so "this specification" cannot be "maintained". 2. Introduction The first two paragraphs of this section do not connect easily. It seems that second paragraph should start like this: 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]. The subtypes under under this top-level type specify different representation formats for fonts (e.g. bitmap or outline formats). However, "bitmap" and "outline" are just general properties or styles, not font representation standards, so really those words should be replaced by the names of specific font representations, say "(e.g., bitmap formats like ABC and outline formats like XYZ)". 3. Background and Justification The names application/x-font-ttf application/font-woff application/font-sfnt are mentioned in the text as being in current use, but only application/font-woff is listed as a deprecated alias of a registered type. The other two should also be listed as deprecated aliases of the proper new types. The use of application/vns.ms-fontobject should be discussed. It seems like you'd want it to be a deprecated alias as well, but the politics of deprecating that name might be complex. registered as MIME subtypes under the "application" top-level type That should be "media subtypes". 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. Media types use the term "parameter" rather than "attribute". The W3C WebFonts WG decided that the situation can be significantly improved [...] Is there a reference for this decision? It is a significant part of the justification for this registration, and so should be documented.. the widespread adoption of IANA's recommendations What "recommendations" are these? 4. Security considerations Depending on the format used to represent the glyph data the font may contain TrueType [truetype-wiki], PostScript [postscript-wiki] or SVG [svg-wiki] outlines and their respective hint instructions, where applicable. The construction "may contain ... where applicable" is awkward, as both parts indicate possible-but-not-mandatory. I suggest removing "where applicable". Many existing (TrueType, OpenType [opentype-wiki] and OFF, SIL Graphite, WOFF, etc.) font formats [...] This reads awkwardly. Better "Many existing font formats (TrueType [...]) [...]". in a way that would not affect existing font rendering engines and text layout implementations. Better "in an upward-compatible way". Indeed, fonts are sufficiently complex, and most (if not all) interpreters cannot be completely protected from malicious fonts without undue performance penalties. The significance of "are sufficiently complex" is unclear. Do you mean, "fonts are sufficiently complex that most ..."? 5. IANA Considerations This specification requires IANA to modify the rules for the existing Internet Media Types registry by adding a new font top-level type in the standards tree, updating the media types registration form [Media-Type-Registration], and registering several subtypes. This is better said: 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. Also, it helps greatly if all of the IANA registration operations are within the section titled "IANA Considerations". See RFC 7322 section 4.8.3. So sections 6 and 7 should be demoted to sections 5.1 and 5.2. 6. 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 font data [...] I think you want "to process it as font data". the subtypes defined within a "font" tree will name the specific font formats. Since this is, in fact, part of the specification of "font", I think you want to say it in the present tense, "the subtypes defined within the "font" tree name the specific font formats". 7. Defined subtypes Would "Subtype Registrations" be more correct? There really aren't any "undefined subtypes" that are considered to exist. In this section the initial entries under the top-level 'font' MIME type are documented. I think "specified" rather than "documented". Also, change "MIME type" to "media type". Optional parameters: In general, parameter names seem to be specified using lower case, though they are case-insensitive, so you may want to lower-case your parameter name definitions. 7.1. Generic SFNT font type This parameter can be used to specify the type of outlines supported by the font. I don't think "supported by" is the best here. Perhaps "provided by". Similarly for other uses of "supported". this optional parameter is a list containing one or more items, separated by commas, with optional whitespace. I strongly recommend against allowing whitespace in parameter values. It seems to be allowed in principle (RFC 6838 section 4.3), but I expect many processors of media types to misbehave on parameter values containing whitespace. I can see why a comma-separated list is necessary, but that means that "Values: TTF, CFF, SVG" is not strictly correct. Perhaps something like the following (and let IANA figure out how to express that in http://www.iana.org/assignments/media-type-sub-parameters/media-type-sub-parameters.xhtml): Values: a comma-separated subset of: TTF, CFF, SVG Similarly for other parameters which can take a comma-separated list of defined values. Parameter definitions seem to need specification of registration procedures. (See the sub-type-parameter registry mentioned above; each parameter has a listed registration procedure.) Interoperability considerations: As it was noted in the first paragraph of the "Security considerations" section, the same font format wrapper can be used to encode fonts with different types of glyph data represented as either TrueType or PostScript (CFF) outlines. This isn't phrased quite right. Perhaps "a single font file can contain encoding of the same glyphs using several different representations, e.g., both TrueType and PostScript outlines". Existing font rendering engines may not be able to process some of the particular outline formats, and downloading a font resource that contains unsupported glyph data format would Change "unsupported glyph data" to "only unsupported glyph data" -- as long as the font contains one format supported by the engine, downloading the font is useful. result in inability of application to render and display text. This seems unlikely; rather the engine would have to use some default font. So say "... would be futile". Therefore, it would be extremely 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. Change "it would be" to "it is", or better, "it is useful to provide a way to identify the format". (Which begs the question of whether there is an efficient way for the browser to determine the media type parameter without downloading the font -- how does the browser get the media type of the font file without a GET?) Similar, another optional parameter is suggested to identify the type of text Better as "Similarly, another optional parameter identifies". Please note that as new outline formats and text shaping mechanisms may be defined in the future, the set of allowed values for two optional parameters defined by this section may be extended. This should probably be stated under the registration procedures for the values of these parameters. This possibility is subtly different from simply adding to a list of allowed values; it warns the implementation that the sub-values within the comma-separated list may be unknown and if so, only the known values should be processed. Indeed, that should probably be said more explicitly: Registration procedures: Expert Review (?) Note that new 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. -- Applications that use this media type: Any and all applications that "Any and all" sounds rhetorical. Better to say just "All". 7.2. TTF font type Similar comments as for section 7.1 Indeed, isn't 7.2 just a subset of 7.1? Why is it separately defined? 7.3. OTF font type Similar comments as for section 7.1 Indeed, isn't 7.3 just a subset of 7.1? Why is it separately defined? 7.4. Collection font type Similar comments as for section 7.1 Indeed, isn't 7.3 just a subset of 7.1? Why is it separately defined? 7.5. WOFF 1.0 Macintosh Universal Type Identifier code: "org.w3c.woff" Is this part of a media type registration? (If so, is it required for all "font" subtypes?) 7.6. WOFF 2.0 Fragment Identifiers Optional, for collections encoded as WOFF Fragment identifiers are always optional, since an HTTP request never identifies the fragment. Fragment Identifiers Optional, for collections encoded as WOFF 2.0. 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 (or the only font, if it is not a collection). If a fragment is specified, and the WOFF does not encode a collection, the fragment is ignored. This is awkward. Maybe better: 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. Of course, this assumes that the collection has an implicit order, but I assume that you know that is true. 8. New Registrations 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 and the ABNF must be followed. Also, an @font- face format should be supplied and, if used, a definition of the fragment identifier syntax for the new type. This is really the "registration procedures" for the "font" type. So I'd move this to section 5. I'm not sure what "the ABNF" is that must be followed, but that seems a redundant statement, as if there is a prescribed ABNF, then necessarily it must be followed. 9.2. Informative References [cff-wiki] "CFF", <https://en.wikipedia.org/wiki/ PostScript_fonts#Compact_Font_Format>. This reference isn't referenced in the text. [postscript-wiki] "PostScript". This reference contains no bibliographic information. 9.3. URIs If these are intended to be in the final RFC, they should be changed into proper references. If they aren't intended to be in the final RFC, this section should have a note to the RFC Editor to delete it. Dale