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Subject: Re: [geda-user] Cross project collaboration on data models
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From: John Doty <jpd AT noqsi DOT com>
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Date: Tue, 22 Dec 2015 12:31:44 -0700
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On Dec 22, 2015, at 10:52 AM, Peter Clifton =
(petercjclifton AT googlemail DOT com) [via geda-user AT delorie DOT com] =
<geda-user AT delorie DOT com> wrote:

> On 22 December 2015 at 17:38, John Doty <jpd AT noqsi DOT com> wrote:
>=20
>> The one thing that led to many corrupted schematics in one of my =
projects was a change in the attribute promotion policy, promoting =
attributes that I had intended to control in heavy symbols. That made a =
real mess. I suppose that the developer who made the change thought it =
would be helpful, but it was a naughty thing to do.
>=20
> Urg... I will go bang my head hard against a wall if that turned out
> to be something _I_ was responsible for. Definitely a naughty thing to
> do.
>=20
> Was this recently, or some time back?

Maybe five years ago.

> (Peter B and I always pushed
> very hard to avoid breaking things like that - existing user designs
> not breaking was a golden golden rule).

Yes. Maybe to a fault. Even I thought it OK to fix the attribute =
censorship bug, since it involved unstable, difficult to predict =
behavior. Peter disagreed, so all we did was enable a user fix.

>=20
> Generally useful, but needs to be explicitly called out by the target
> netlister I think.

An interesting possibility. Some netlisters don=92t do useful things =
with an unflattened netlist. On the other hand, some (like the SPICE =
netlisters) can work either in flattened or unflattened mode, so you =
need some way to choose.

Some of the gnetlist Scheme primitives have an extra, unused, =93level=94 =
attribute that Ales seems to have intended to use as a control for =
partial flattening. Viewlogic had a similar thing back in the day, but =
it never worked well. Maybe there=92s a design that could work?

> (I recall gnetlist flattens by default, and acts on
> attributes that have their meaning pretty hard-coded).

Some are hard coded. Off the top of my head, refdes, pinnumber, =
numslots, slotdef, slot, pinseq, netname, net, and graphical. A subtle =
peculiarity of graphical=3D1 that doesn=92t seem to cause much trouble =
is that there are really two different cases:

1. Genuinely graphical objects that have no effect on the netlist, such =
as a title block.

2. Objects that communicate something about a connected net, most =
commonly its name.

>=20
> Another example, our implementation of slotting, makes makes shudder
> somewhat. It is one of the few cases where gEDA throws away its
> complete core agnosticism over attached attributes etc.

An associated problem is that slotting uses pinseq in a hard-coded way =
to identify pin function, but some back ends use it to order the pins in =
a netlist. These are not always compatible.

> .  We should
> have introduced a more generic mechanism, then "activated" (probably
> with a work-flow specific plugin) it for designs which need that
> behaviour.

Yes.

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



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