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Subject: Re: [geda-user] The nature of gEDA layers
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From: John Doty <jpd AT noqsi DOT com>
In-Reply-To: <CAJZxidDmjMtd_fKvR5qZVRa+hwDUbvfaz79oZjkBgDuE1m8RBg@mail.gmail.com>
Date: Wed, 27 Jan 2016 12:02:23 -0700
Message-Id: <53ABCB1C-0306-4DF8-98A9-88F8CC6B8E80@noqsi.com>
References: <alpine DOT DEB DOT 2 DOT 00 DOT 1601180756390 DOT 9035 AT igor2priv> <alpine DOT DEB DOT 2 DOT 00 DOT 1601260416150 DOT 9035 AT igor2priv> <56A751EC DOT 8030402 AT iae DOT nl> <20160126124701 DOT 0d061912c7e078ced9d4e6cb AT gmail DOT com> <CANEvwqgs3YFnt7m8mA1DN6X2KdWbyr4zpXCVH321vDo1f7CyxA AT mail DOT gmail DOT com> <201601261804 DOT u0QI4KEQ009550 AT envy DOT delorie DOT com> <E7D351BF-5BBB-41AC-B996-D5E27079A82C AT noqsi DOT com> <CAC4O8c-ZyNnCzCDHXkYYabSD4fG8vf+CKmhMycNJujGMPKzQDQ AT mail DOT gmail DOT com> <s6nr3h49hrq DOT fsf AT blaulicht DOT dmz DOT brux> <DDB07351-7C94-4B5C-99FA-83750CD4592A AT noqsi DOT com> <20160126233332 DOT dec2f06f5c74354a3841989c AT gmail DOT com> <s6n1t93h4ub DOT fsf AT blaulicht DOT dmz DOT brux> <20160127091746 DOT 1c7a976c2752f913921688ac AT gmail DOT com> <s6npowne74w DOT fsf AT blaulicht DOT dmz DOT brux> <20160127141334 DOT c738feb9dbeb54a7dec3dff8 AT gmail DOT com> <s6n37tjt1tv DOT fsf AT falbala DOT ieap DOT uni-kiel DOT de> <56A8F74B DOT 8080304 AT ecosensory DOT com> <CAC4O8c9UKLsh5FAAwUMEtHThKH-w3gUmCU2i9dRW9igkyRt-TQ AT mail DOT gmail DOT com> <CAJZxidDmjMtd_fKvR5qZVRa+hwDUbvfaz79oZjkBgDuE1m8RBg AT mail DOT gmail DOT com>
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On Jan 27, 2016, at 11:40 AM, Chad Parker (parker DOT charles AT gmail DOT com) =
[via geda-user AT delorie DOT com] <geda-user AT delorie DOT com> wrote:

> Hello-
>=20
> I realize 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 find useful.

Oh, no. The way it works around here, you lose cred by contributing to =
the discussion ;-)

>=20
> I would suggest that a layer is really more of a container than =
anything else, it is a way of collecting and grouping objects.

I would not call that a layer at all. A layer represents a hunk of =
copper, epoxy glass, ink, etc. What you=92re talking about should be =
called a =93pattern=94, I think: it edits the arrangement of material on =
one or more layers.

> Ultimately the group of objects is interpreted in a particular way =
when a board 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 the physicality of them is an =
interpretation.

That=92s why you should not use the term =93layer=94 here: it promotes =
confusion.

> Keep the concept of a layer simple, and let the concerns of =
interpretation and realization happen at a higher level such as DRC, a =
board house, a chip fab, a technician, etc.
>=20
> 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 core of pcb. I don't know if anyone has thought much about a version =
road map, but such major architectural changes tend to happen as new =
major version 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 the next version with the new core.
>=20
> This is just my 2 cents.
> Cheers,
> --Chad
>=20
>=20
>=20
> 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] =
<geda-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=F6ttcher 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.  Including the layer that tells what is conductively
> >> connected.
> >
> >
> > This needed a new subject line.
> >
> > How about my proposal of the previous email, "layers correspond and
> > represent physical planar layers,
> > and outline is a special mask layer that acts on physical layers.  =
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
>=20
> Seem mostly reasonable but I'd still hesitate a bit.  Advertising
> 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".  It's possible that the current representation
> might have multiple useful physical realizations, and once you start
> making assumptions about precise physical meaning some of them might
> be lost.
>=20
> Britton
>=20
>=20

John Doty              Noqsi Aerospace, Ltd.
http://www.noqsi.com/
jpd AT noqsi DOT com



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<html><head><meta http-equiv=3D"Content-Type" content=3D"text/html =
charset=3Dwindows-1252"></head><body style=3D"word-wrap: break-word; =
-webkit-nbsp-mode: space; -webkit-line-break: =
after-white-space;"><br><div><div>On Jan 27, 2016, at 11:40 AM, Chad =
Parker (<a =
href=3D"mailto:parker DOT charles AT gmail DOT com">parker DOT charles AT gmail DOT com</a>) =
[via <a href=3D"mailto:geda-user AT delorie DOT com">geda-user AT delorie DOT com</a>] =
&lt;<a href=3D"mailto:geda-user AT delorie DOT com">geda-user AT delorie DOT com</a>&gt;=
 wrote:</div><br class=3D"Apple-interchange-newline"><blockquote =
type=3D"cite"><div =
dir=3D"ltr"><div><div><div><div><div><div>Hello-<br><br></div>I realize =
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 find =
useful.<br></div></div></div></div></div></div></blockquote><div><br></div=
>Oh, no. The way it works around here, you lose cred by contributing to =
the discussion ;-)</div><div><br><blockquote type=3D"cite"><div =
dir=3D"ltr"><div><div><div><div><div><br></div>I would suggest that a =
layer is really more of a container than anything else, it is a way of =
collecting and grouping =
objects.</div></div></div></div></div></blockquote><div><br></div>I =
would not call that a layer at all. A layer represents a hunk of copper, =
epoxy glass, ink, etc. What you=92re talking about should be called a =
=93pattern=94, I think: it edits the arrangement of material on one or =
more layers.</div><div><br><blockquote type=3D"cite"><div =
dir=3D"ltr"><div><div><div><div> Ultimately the group of objects is =
interpreted in a particular way when a board 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 the =
physicality of them is an interpretation. =
</div></div></div></div></div></blockquote><div><br></div>That=92s why =
you should not use the term =93layer=94 here: it promotes =
confusion.</div><div><br><blockquote type=3D"cite"><div =
dir=3D"ltr"><div><div><div><div>Keep the concept of a layer simple, and =
let the concerns of interpretation and realization happen at a higher =
level such as DRC, a board house, a chip fab, a technician, =
etc.<br><br></div>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 core of pcb. I don't know if anyone has thought much =
about a version road map, but such major architectural changes tend to =
happen as new major version 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 the next version with the new =
core.<br><br></div>This is just my 2 =
cents.<br></div>Cheers,<br></div>--Chad<br><div><br><br></div></div><div =
class=3D"gmail_extra"><br><div class=3D"gmail_quote">On Wed, Jan 27, =
2016 at 12:32 PM, Britton Kerin (<a =
href=3D"mailto:britton DOT kerin AT gmail DOT com">britton DOT kerin AT gmail DOT com</a>) =
[via <a href=3D"mailto:geda-user AT delorie DOT com">geda-user AT delorie DOT com</a>] =
<span dir=3D"ltr">&lt;<a href=3D"mailto:geda-user AT delorie DOT com" =
target=3D"_blank">geda-user AT delorie DOT com</a>&gt;</span> =
wrote:<br><blockquote class=3D"gmail_quote" style=3D"margin:0 0 0 =
.8ex;border-left:1px #ccc solid;padding-left:1ex"><span class=3D"">On =
Wed, Jan 27, 2016 at 7:58 AM, John Griessen &lt;<a =
href=3D"mailto:john AT ecosensory DOT com">john AT ecosensory DOT com</a>&gt; =
wrote:<br>
&gt; On 01/27/2016 10:38 AM, Stephan B=F6ttcher wrote:<br>
&gt;&gt;&gt;<br>
&gt;&gt;&gt; There is no via layer,<br>
&gt;&gt;<br>
&gt;&gt; Yes there is, in my proposeal.<br>
&gt;&gt;<br>
&gt;&gt;&gt; &gt;a via is a composite of objects on different =
layers.<br>
&gt;&gt;<br>
&gt;&gt; That is true.&nbsp; Including the layer that tells what is =
conductively<br>
&gt;&gt; connected.<br>
&gt;<br>
&gt;<br>
&gt; This needed a new subject line.<br>
&gt;<br>
&gt; How about my proposal of the previous email, "layers correspond =
and<br>
&gt; represent physical planar layers,<br>
&gt; and outline is a special mask layer that acts on physical =
layers.&nbsp; Via could<br>
&gt; also be in the mask layer<br>
&gt; category -- mask layers "act on" physical definition layers...<br>
&gt;<br>
&gt; I'd like to call them that way --<br>
&gt; mask layers<br>
&gt; physical definition layers<br>
<br>
</span>Seem mostly reasonable but I'd still hesitate a bit.&nbsp; =
Advertising<br>
layers as having particular physical meaning is both more ambitious<br>
and more limiting than just having them be "something like what they<br>
look like in pcb".&nbsp; It's possible that the current =
representation<br>
might have multiple useful physical realizations, and once you start<br>
making assumptions about precise physical meaning some of them might<br>
be lost.<br>
<br>
Britton<br>
<br>
</blockquote></div><br></div>
</blockquote></div><br><div apple-content-edited=3D"true">
<span class=3D"Apple-style-span" style=3D"border-collapse: separate; =
border-spacing: 0px 0px; color: rgb(0, 0, 0); font-family: Helvetica; =
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normal; letter-spacing: normal; line-height: normal; text-align: auto; =
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white-space: normal; widows: 2; word-spacing: 0px; "><p style=3D"margin: =
0.0px 0.0px 0.0px 0.0px"><font face=3D"Helvetica" size=3D"3" =
style=3D"font: 12.0px Helvetica">John Doty<span =
class=3D"Apple-converted-space">&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;<span =
class=3D"Apple-converted-space">&nbsp;</span><span =
class=3D"Apple-converted-tab">&nbsp; &nbsp;<span =
class=3D"Apple-converted-space">&nbsp;</span></span></span>Noqsi =
Aerospace, Ltd.</font></p><p style=3D"margin: 0.0px 0.0px 0.0px =
0.0px"><a href=3D"http://www.noqsi.com/">http://www.noqsi.com/</a></p><p =
style=3D"margin: 0.0px 0.0px 0.0px 0.0px"><font face=3D"Helvetica" =
size=3D"3" style=3D"font: 12.0px Helvetica"><a =
href=3D"mailto:jpd AT noqsi DOT com">jpd AT noqsi DOT com</a></font></p><br =
class=3D"Apple-interchange-newline"></span>
</div>
<br></body></html>=

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