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Date: Tue, 30 Jun 2015 17:45:47 -0400
From: "Dan McMahill (dan AT mcmahill DOT net) [via geda-user AT delorie DOT com]" <geda-user AT delorie DOT com>
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Subject: Re: [geda-user] Interchange formats
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Reply-To: geda-user AT delorie DOT com

On 6/10/2015 4:26 PM, Evan Foss (evanfoss AT gmail DOT com) wrote:
> For those of us who are not as well versed in our history of this
> subject. I would like to know why so many common EDA formats have
> failed?
>

Keeping in mind that this is only my opinion, I think one of the issue 
is that you have two tools.  EDA1 and EDA2.  They may store different 
data.  Not just store data differently, but store different data.  Here 
is an example that has come up here recently.  PCB stores rotated 
footprints as opposed to a footprint and a rotation to be applied. 
Some other tool may store the footprint and a rotation and another tool 
may store a pointer to a footprint in a library as opposed to storing a 
copy of the footprint.

Now suppose you have a format which by some miracle can actually store 
all the data that either program stores.  But what do you do on reading 
it in?  You have data that one program wrote out but the other doesn't 
use.  Or even if it does use it for import it may not use it past then. 
  Using the footprint example, maybe PCB could load a footprint from 
some interchange file and rotate per the stored rotation but that is 
then lost in the internal database.  This means a round trip translation 
(EDA1 to interchange to EDA2 to interchange to EDA1) will not produce 
something identical to where you started.

It seems to me then that what is needed for a true standard format is 
that the internal database contents (not the format but what actually is 
stored and manipulated) and how that data is used has to be part of the 
standard.  This is much more invasive into program internals than a 
format which is basically output only (like gerber file).  Now you get 
into a whole turf war over whose program gets to be closer to "standard" 
and also issues over what is proprietary or not.

Just my opinion.

-Dan