Martin Thomson <m...@lowentropy.net> wrote:
> On Wed, May 7, 2025, at 00:09, Michael Richardson wrote:
>> I think that the packet diagrams *are* normative as to the structure of
the
>> packet structure. But that we should never put BCP14 language in the
diagram.
> I think that many people think of packet diagrams as normative, but I'm
> convinced that this is both inaccurate and unnecessary.
> Consider ASN.1 or other schema languages, which are - to a very broad
> approximation - accessible. Those can be normative. I don't think
> that ASCII art can be, except in a few quite narrow cases. The
> normative purpose in those cases is probably better served by a formal
> schema language.
Yes... but I think that most sighted people look at the diagrams.
That TLVs and the like, while they require some additional text, are still
quite understandable. In particular, the position of bit flags is almost
always only defined in the diagram. Maybe that's a bug.
On the topic of schema languages, a company I worked for 25 years ago tried
to advance. For instance, here is our favorite 791:
https://datatracker.ietf.org/doc/html/draft-nossik-pax-pdl-00#section-3.7.1
We had code to generate diagrams in the classic form, but I don't think it
ever got off Felix or Alan's desk.
> If we are to achieve our accessibility goals, there are two angles that
> we should consider concurrently:
> * Alternative text descriptions of diagrams. I personally find these
> tedious to generate and often question the value of them.
Yes.
> * Ensuring that the text contains a complete specification. This is
> the attitude that was drilled into me and I've become convinced that it
> works. It's possibly the only thing that works reliably.
I still have the bison grammar for PDL :-)
(Our PDL compiler generated "code" for our classifier, which was not turing
complete)
--
Michael Richardson <mcr+i...@sandelman.ca>, Sandelman Software Works
-= IPv6 IoT consulting =- *I*LIKE*TRAINS*
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