[freearchitecture] An open CAD file format

[Bruno Postle]

On Wed 12-Feb-2003 at 07:48:30 +0000, Chris Croome wrote:
> 
> If not I wonder what the easiest way of creating a versionable
> drawing format would be?

Ok, I'll bite, even though I'm *never* going to implement this.

Here are my requirements for a properly open and RCS-able CAD file
format:

1. Text only, <cr><lf> delimited, human readable.

   In general, all information should be in 'Key -> Value' format,
   one item per line, there should be no unlabelled data.

2. Blocks/references have full inheritance and polymorphism.

   References can be referenced themselves, any aspect of a
   reference can be overridden and modified.  AutoCAD is dreadful in
   this respect.

3. Resources (images, multiline text blocks) exist as separately
   editable files, not embedded in larger files.

   An image should exist as a file on the filesystem, it should be
   editable directly using existing tools.  Same for text and any
   other embedded non-drawing object - No OLE.

4. Changes to drawing objects can be made in-place without
   regenerating/reordering the whole dataset.

   This is crucial for efficient use of versioning systems.  Patch
   files should generally be apply-able even when the offsets have
   changed.

If I get going, I might describe a format that meets this criteria
:-)

-- 
Bruno