[Matroska-devel] EBML specification component for review - About this Document

Moritz Bunkus moritz at bunkus.org
Fri May 1 12:05:53 CEST 2015


Hey,

> Although the RFC draft was in draft stage, the EBML specification at
> matroska-org.github.io/libebml/ isn’t. I suggest not moving this to
> the EBML spec.

This reminds me: what is our goal? Currently we have two documents. For
me the goal is to come out of this process with only one document
superseding the older two. While RFCs may not be the easiest things to
read for human beings they are the de-facto standard for technical
specification in the internet.

Therefore I think our goal should be: create an EBML RFC, remove the two
older documents.

So »moving to the EBML spec« is not something I would suggest in general
anyway – unless the EBML spec is the one document we want to bring into
proper RFC shape.

Just to be clear what we are talking about.

> RFC2119 is decent boilerplate for this type of specification. Though
> the use of these terms in the EBML specification is fairly low: 1
> shall, 1 should, and 2 may.

Doesn't matter if our goal is an RFC. If it is then the RFC2119
boilerplate is necessary.

> In all cases the RFC2119 meaning seems appropriate. For instance for
> "All level 1 elements should include a CRC-32” should in RFC2119 terms
> means RECOMMENDED which sounds about right since it’s rare that I see
> EBML with CRCs in this way, but it ‘should’ happen.

I agree.

> This section on ABNF expression appears in the RFC draft and the
> resulting expressions are used recurrently in the draft, but the EBML
> specs don’t include this. In part these seems to be because what the
> RFC draft expresses in ABNF is expressed in the EBML spec via an HTML
> table. For the purposes of submitting an EBML spec to the IETF I can
> see why Martin rewrote much of this in ABNF to meet the usual RFC
> formatting, but for reviewing the specification I prefer the table
> view of the EBML spec. Perhaps there does need to be two concurrent
> versions of the spec, one formal for IETF and one for pretty web
> display.

This is exactly what I'm talking about above. We should be clear about
this before we continue any further.

I disagree that we should have two documents. Two documents always means
manual synchronization between the two which is error-prone. Also there
are formats out there specified solely by RFCs, e.g. the specs around
Xiph's Opus codec[1].

> Any preference for how to deal with this? I like the specdata.xml
> approach where one document is used to generate outputs for different
> purposes.

In this case I cannot think of a way of generating such widely distinct
formats from a single source of information. At least not for all parts
of the specification.

It may be possible for the Matroska side of things, but for EBML at
least I'd rather stick with a single RFC document, get some experience
with the process and re-visit this question when we start working on the
Matroska specs.

BTW: Have you been able to reach Martin Nilsson yet?

Kind regards,
mosu

[1] http://www.opus-codec.org/docs/
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