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Date:	Tue, 1 Sep 2015 15:30:47 -0400
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From:	DJ Delorie <dj AT delorie DOT com>
To:	geda-user AT delorie DOT com
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Subject:	Re: [geda-user] back annotation proposal (RFC)
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Reply-To:	geda-user AT delorie DOT com

> The problem is that there are hundreds or even thousands of
> different resistors in my database. I could choose a thru-hole part
> for packaging only to have the pcb layout engineer change it to
> surface mount part or inline sip or dip array. Those changes would
> have to be backannotated from PC layout to the original schematic.
> 
> So here's the problem. You frequently have to take one design into
> multiple PCB's. Your schematic will be used in the real product so
> it must be nice and compact with all surface mount parts. You will
> also use the same schematic to build a "break-out-board" with
> thru-hole parts for testing and code development.

This might be a case where a BOM drives the tools, instead of being an
output file.  Multiple "input BOMs" could be maintained by different
groups and merged as part of the process that generates the final
PCAs.

And by BOM I mean "any data that helps narrow down the part selection"
- it could be a physical list or regex's, rule set, or database of
attribute preferences.  Whatever :-)

My blue sky proposal included the option of "some rule set" which I
never defined, which provides project-specific defaults to help narrow
down the list of available parts to the one actually used.  The idea
was that the designer specified what they needed, and the layouter
would pick from the options given.

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