title: Alibre Design file format
body: <p>Did anyone try to read programmatically an <a href="http://www.alibre.com" rel="nofollow noreferrer">Alibre Design</a> CAD file?<br>
  I see that deep inside a part file (*.AD_PRT) there's an STEP/ISO 10303-21 structure, but I'm wondering about the rest of the file.. Is it proprietary?</p>