Specification based: the format has an exact interpretation of the data. OBJ is an example of this...the format describes triangles and there is only one interpretation of what that triangle could be.
Reality based: the format models real-world concepts; the correct interpretation is "as close to the real world as possible." The nav.dat file is like that.
I have been reading the OpenStreetMap Wiki and hit upon something I didn't realize: you can't use copyright to protect a derived work from a file that simply contains a list of facts!
Now I am a programmer - I am used to writing code, slapping a copyright notice up top, and assuming that it's now mine...heck, I'm the one getting carpel tunnel from typing it out. But consider the nav.dat file; it contains a giant list of frequencies for navaids. It's a fact that the BOS VOR is 112.7. Is my mentioning of that fact in this blog a derived work of the nav.dat file? Of course not, and it's a good thing too because otherwise we wouldn't be able to state facts without IP conflicts.
The OSM guys believe that they need to change their license to something weirder than the CC-BY-SA license they have now because the CC license uses copyright, you can't copyright facts, and OpenStreetMap is really just a huge collection of facts.
Now at this point I've written six paragraphs too many without the obligatory "I am not a lawyer." I am not one. And I must admit, my biggest concern with all of this is that it gets confusing and hard to interpret, and I'd be perfectly happy if there were only 3 or 4 licenses out there for everyone, you'd pick your favorite flavor, and everyone would know what it means.
Suffice it to say, it never occurred to me that a criteria of a file format might be "protectability" - that is, does the file format allow an author to specify something other than facts, so that it is elligible for copyright protection?
If you are an author, the good news is: pretty much all of our file formats would meet that criteria:
- OBJ and DSF are essentially 3-d modeling containers (DSF is just a damned wierd one).
- Images are copyrightable, so that takes care of your textures.
- Plugins are code, clearly copyrightable.
- ACF files contain, among other things, 3-d models, see the first point.
- Apt.dat would be the format most at risk of "factualization", but I think you could argue that the arrangement of bezier curves and attributes is more of an artistic 3-d model than a statement of fact.
(Oh yeah, this whole article is written from an entirely US-centric viewpoint...I am even less qualified to speak of such things outside the US than I am here at home.)