@User: Look at the very bottom of the 2nd link above for "mask level data". That gives the GDS numbers corresponding to the actual masks. That's what you're looking for, although it appears that they use different naming conventions, so fixing that would be helpful. But the values are all there and are non-proprietary.

@Tim Edwards Thanks for the response. I think I see what you're referring to. The entries with "mask", "mask add", or "mask drop" lines, right? What I'm looking for is how the GDS drawing layers are combined to make the actual mask layers. For example, the mask layer cfom (23:0) is most likely the OR of diff (65:20) and tap (65:44).

@Mitch Bailey: I have this information in a PDF, and will add it to one of my online spreadsheets. It is very hard to read, and appears to be just a dump of Calibre rules.

@Tim Edwards Thanks, I appreciate it. I'm assuming that if I write Calibre LVS/DRC rules for sky130, I can release them as open source. Just need to find someone with access to the tools for debugging.

See: https://docs.google.com/spreadsheets/d/1oL6ldkQdLu-4FEQE0lX6BcgbqzYfNnd1XA8vERe0vpE/edit#gid=2006584484 sheet "derived mask layer mappings". The source material is a big mess. I tried to clean it up as best I could.

Thanks. Looks like enough information to get started.