All of this discussion of formats misses the shining example that's already in 
gEDA: the schematic format. Now *there's* a work of genius.

1. The format is based on a small, well-chosen set of elementary objects.

2. Elementary objects are represented by one-line tagged records of fixed 
format (identified by the tag). Almost any tool you might want to use can 
easily process a file of this sort without the need of any special library.

3. A set of objects can be attached to any abject. This can be in principle 
extended to unlimited depth.

4. Multi-line text objects are supported. There are few restrictions on the 
content of a text object.

(1) and (2) make the format easy to process with simple tools. (3) and (4) 
constitute an infinitely flexible escape hatch, although we're not using it to 
its full capability (but a single level of attached attributes is pretty good).

A good file format for this sort of thing avoids definitions for high level 
concepts. It provides mechanisms to compose high level objects from low level 
primitives. So, the question here starts with "what are the primitives that one 
constructs printed circuit board descriptions from?"

John Doty              Noqsi Aerospace, Ltd.
http://www.noqsi.com/
j...@noqsi.com




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