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Date: Tue, 22 Dec 2015 22:15:14 +0100
From: "Nicklas Karlsson (nicklas DOT karlsson17 AT gmail DOT com) [via geda-user AT delorie DOT com]" <geda-user AT delorie DOT com>
To: geda-user AT delorie DOT com
Subject: Re: [geda-user] Cross project collaboration on data models
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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:
> > 
> >> 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.
> > 
> > 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.
> > 
> > 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.
> 
> > 
> > Generally useful, but needs to be explicitly called out by the target
> > netlister I think.
> 
> An interesting possibility. Some netlisters don’t 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, “level” 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’s 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=1 that doesn’t 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.
> 
> > 
> > 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

And more yes.