W3C home > Mailing lists > Public > public-automotive@w3.org > January 2020

Re: VSS Layers introduction

From: Rudolf J Streif <rudolf.streif@ibeeto.com>
Date: Fri, 17 Jan 2020 10:30:24 -0800
To: Gunnar Andersson <gandersson@genivi.org>, W3C Public Automotive <public-automotive@w3.org>
Message-ID: <9c207d61-8629-2ec0-988d-988ef39dc3f4@ibeeto.com>
Actually this statement is not quite correct:

1) Potential for *any number of* layers. (As of now the private branch
acts as a *one* additional "layer" that can override and add data, as
you now described)

It's not limited to a branch called 'private'. What branch is merged and
where is defined by an include in the toplevel
VehicleSignalSpecification.vspec. Now of course this begs the question
what happens if there are multiple includes that modify/amend the same
nodes when there are conflicts? The answer is: "the last one wins" as
the includes are processed in order of appearance in
VehicleSignalSpecification.vspec. That essentially constitutes an
implicit priority.

Layer priority is probably something that you want to add to the slide
"Additional design challenges".


On 1/16/20 9:52 PM, Gunnar Andersson wrote:
> Thanks for pointing that out, Rudi.
> (continued...)
> On Wed, 2020-01-15 at 09:32 -0800, Rudolf J Streif wrote:
>> Functionality of appending and/or modifying a node from one branch
>> with
>> a node from another branch with the same signal path is already
>> available in VSS. 
> [trimmed]
>> https://github.com/GENIVI/vehicle_signal_specification/commit/518dfbeb2a434c9c55ec27e06c84f6e8caf941bd#diff-4a931512ce65bdc9ca6808adf92d8783
> That's great and shows that this thinking was there from the beginning.
> That commit indeed provides an implementation that is a starting point
> for the behavior that this proposal looks for.
>>> The commit message states:
> [trimmed]
>> Now that does not cover everything from Gunnar's slides (in
>> particular
>> there is no wildcard support) but it's a starting point.
> Yes.  And a few other differences that come to mind.  These are things
> that might be added on top of the current model, *if* the layers idea
> were adopted:
> 1) Potential for *any number of* layers. (As of now the private branch
> acts as a *one* additional "layer" that can override and add data, as
> you now described)
> 2) A proposal of layers as parallell files in the same directory tree
> -- with different file suffix --  (it would complement the current
> model that places /private as a parallel directory subtree)
> 3) The presentation hints at some additional higher level concepts that
> would allow defining metadata about the layers themselves.
> and as a corrollary it also suggests that we are effectively defining 
> some varying file types.  I.e. they might not be formally .vspec" files
> but something else.   (The current /private "layer" does not explicitly
> make a distinction, and basically assumes ".vspec" files to be there).
> I'm not sure how important that is but it seemed useful to me.
> Best Regards,
> - Gunnar
> P.S. Since we are now talking about VSS specifics, I expect the details
> of this will be sorted out using GitHub issues, but if it is in the
> interest of the W3C participants then of course by all means feel free
> to continue the discussion here.
> It's a great start however.
>> :rjs
>> On 1/14/20 12:26 PM, Gunnar Andersson wrote:
>>> As requested today, here is a link to the introduction/rationale
>>> slides
>>> for "VSS Layers".   
>>> A small caveat, this presentation is a work in progress and
>>> describes
>>> the rationale on a very fundamental level.  The idea is simple of
>>> course, and very generic, because it is useful/needed in a whole
>>> bunch
>>> of areas, not only for access control even if that that was one of
>>> the
>>> driving areas.
>>> There of course needs to be some work to tie this into the W3C
>>> protocol
>>> specifics by means of examples etc.  We concluded today that it is
>>> basically in line with what is needed in Ulf's recent
>>> implementation
>>> work as well as previous similar things that Daniel mentioned had
>>> been
>>> tried in his organization in the past, so hopefully this is useful,
>>> even if it does not today provide all the concrete examples in the
>>> W3C
>>> protocol context.
>>> Happy to have the discussion about comparing this to previous
>>> similar
>>> ideas and to define more of the details.
>>> Thanks,
>>> - Gunnar
>>> [1] 
>>> https://at.projects.genivi.org/wiki/pages/viewpageattachments.action?pageId=40402952&sortBy=date&highlight=VSS+composable+layers+-+draft+20200114.pdf&&preview=/40402952/47711024/VSS%20composable%20layers%20-%20draft%2020200114.pdf
>>> or shorter:
>>> https://bit.ly/2TnrV05
Rudolf J Streif
CEO/CTO ibeeto
+1.855.442.3386 x700

Received on Friday, 17 January 2020 18:30:34 UTC

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