Hello-

I realiz= e I'm not a frequent contributor to these discussions, and consequently= have no real "street cred", so feel free to disregard my remarks= . With that said, perhaps I can provide a perspective that someone will fin= d useful.

I would suggest that a layer is really more of a con= tainer than anything else, it is a way of collecting and grouping objects. = Ultimately the group of objects is interpreted in a particular way when a b= oard is fabricated, perhaps as copper, perhaps as a board outline, perhaps = as a silkscreen... or perhaps as something else entirely. Anyway, the point= is that the concept of a layer is really a more general abstraction and th= e physicality of them is an interpretation. Keep the concept of a layer sim= ple, and let the concerns of interpretation and realization happen at a hig= her level such as DRC, a board house, a chip fab, a technician, etc.

The other comment I would make, is that it seems like some of these = discussions could be leading towards some very fundamental changes in the c= ore of pcb. I don't know if anyone has thought much about a version roa= d map, but such major architectural changes tend to happen as new major ver= sion releases. If in fact such major changes are actually being considered = for implementation, it may be well worth it to sketch out a map so you can = see where effort is best expended. For example, which bugs do you actually = want to fix in the current version and what things are better worked into t= he next version with the new core.

This is just my 2 cents.

Cheers,

--Chad

On Wed, Jan 27, 2016 at 12:32 PM, Britton Kerin (britton DOT kerin AT gmail DOT com) [via geda-user AT delorie DOT com] <ged= a-user AT delorie DOT com> wrote:

= On Wed, Jan 27, 2016 at 7:58 AM, John Griessen <john AT ecosensory DOT com> wrote:
> On 01/27/2016 10:38 AM, Stephan B=C3=B6ttcher wrote:
>>>
>>> There is no via layer,
>>
>> Yes there is, in my proposeal.
>>
>>> >a via is a composite of objects on different layers.
>>
>> That is true.=C2=A0 Including the layer that tells what is conduct= ively
>> connected.
>
>
> This needed a new subject line.
>
> How about my proposal of the previous email, "layers correspond a= nd
> represent physical planar layers,
> and outline is a special mask layer that acts on physical layers.=C2= =A0 Via could
> also be in the mask layer
> category -- mask layers "act on" physical definition layers.= ..
>
> I'd like to call them that way --
> mask layers
> physical definition layers

Seem mostly reasonable but I'd still hesitate a bit.=C2=A0 Adver= tising
layers as having particular physical meaning is both more ambitious
and more limiting than just having them be "something like what they look like in pcb".=C2=A0 It's possible that the current representa= tion
might have multiple useful physical realizations, and once you start
making assumptions about precise physical meaning some of them might
be lost.

Britton

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