I've always wondered how something like an Autodesk Inventor sldprt file was formatted so that I could write a program to manipulate those files. I assumed it

I've always wondered how something like an Autodesk Inventor sldprt file was formatted so that I could write a program to manipulate those files. I assumed it was proprietary and left it at that. A few years later, I saw that Onshape allows importing sldprt files into their system and I wonder how they were able to provide that ability without some proprietary knowledge transferred