Re: A modest proposal on extensibility

Sent from my iPhone

On Oct 10, 2014, at 1:55 PM, Richard Barnes <rlb@ipv.sx> wrote:

On Fri, Oct 10, 2014 at 4:34 PM, Mark Watson <watsonm@netflix.com> wrote:

> This seems fine, except:
> - we have discussed key format and agreed we do not want / need
> extensibility for this
> - no one has suggested we need an extensibility point for usages
>

I agree that key formats are low priority for extension, but I'm a little
surprised that we would forego it entirely.  I guess it just means that
extending the set would need a spec update (to add extensibility), which
seems OK.


> I'd suggest that we include a table which lists all the WebCrypto
> algorithms and for each one lists the specification(s) that define
> that algorithm. The initial value for the existing algorithms will be
> 'This specification' but we will add values - through the errata
> process - as we write extension specifications.
>
> The definition of 'other specifications' will be revised to be
> restricted to those specifications listed in the table.
>

This seems fine to me.



> The only remaining issue is whether we should arrange the procedures
> for import / export of keys for algorithms parameterized by a hash
> function such they it does not appear that import /  export for the
> existing cases can be overridden, even though we constrain extensions
> to definition of new hash algorithm values in prose.
>

That was what I was trying to get at with the proposed branch structure:
-- One of the hash functions defined in this spec...
-- Another one you recognize...
-- Error


It's not quite as simple as that in the specification text as we want to
defer to the extension specification exactly how the new hash function is
signalled, including the possibility that it is parameterized. But still,
we can do this.

...Mark


--Richard



> ...Mark
>
> Sent from my iPhone
>
> > On Oct 10, 2014, at 8:45 AM, Harry Halpin <hhalpin@w3.org> wrote:
> >
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> >
> >
> >> On 10/10/2014 05:27 PM, Richard Barnes wrote:
> >> Talking to a few folks off-list, it seems like the extensibility
> >> discussion has gotten a bit muddled.  The goal of this message is
> >> to try to focus/clarify with a specific proposal.   It sounds like
> >> the general desiderata people have are: 1. To make it possible to
> >> add new values for strings/enums without major spec surgery 2. To
> >> make it easy for developers to find extensions
> >>
> >> To that end, I would like to propose a way forward for
> >> extensibility:
> >>
> >> <proposed-plan>
> >>
> >> 1. Wherever a string/enum value is defined, insert something like
> >> the following: 1.1. This specification defines values X, Y, Z 1.2.
> >> Implementations MAY support other values 1.3. When an extension is
> >> made to add a value, a reference should be added to the
> >> "Extensions" section
> >>
> >> 2. Wherever a string/enum value is used as a branch point, insert
> >> something like the following: 2.1. If X... If Y... If Z... 2.2. If
> >> another recognized value, process according to that value 2.3. If
> >> an unrecognized value, raise an NotSupportedError (or TypeError
> >> for enums)
> >>
> >> 3. Add an "Extensions" section to the bottom of the spec, where
> >> links can be added to point to extension specs.
> >
> > As noted on Bugzilla, as long as Extensions are in Errata, that's fine
> > by W3C Process I believe.
> >
> >   cheers,
> >        harry
> >
> >>
> >> </proposed-plan>
> >>
> >> Does that overall approach seem agreeable to people?
> >>
> >> --Richard
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