I am completely lost.

Also I am using a vision only machine. Is it realistic to think that I can write an entire working program just using a DXF file and not an actual part?

Anything is possible if you have the time!

Anyways, it's not probable to have a perfectly good, working program, first try, without any CMM involvement. You have to adjust lighting parameters, focus, and the like.
It's do-able, don't get me wrong.

I've never used DXF with PC-DMIS, however I'm under the impression it's basically 2D CAD with point data.
Using this, you can program in every single feature you want to check, have your alignments all set up, the whole nine.

HOWEVER, you will still have to stick the part on the machine and verify it runs through correctly before you can consider it a "finished" part.
9/10 times, even IF you create a perfectly good, working program, first try, you'll have to adjust the focus, lighting, and filtering, as this is impossible without prior knowledge of how the camera will "see" the part.

It's not so much different from using a touch probe, once you get around the fact that there's not a physical tip.
Get everything programmed on your DXF as best as you can, chuck it in the CMM and hope for the best. (Obviously, run it slow first!)

As mentioned above, you will need a manual alignment in the beginning to tell the machine where the part is. From there, using the DXF nominals, it should be able to take points/scans effectively

Also I am using a vision only machine. Is it realistic to think that I can write an entire working program just using a DXF file and not an actual part?

Anything is possible if you have the time!

Anyways, it's not probable to have a perfectly good, working program, first try, without any CMM involvement. You have to adjust lighting parameters, focus, and the like.
It's do-able, don't get me wrong.

I've never used DXF with PC-DMIS, however I'm under the impression it's basically 2D CAD with point data.
Using this, you can program in every single feature you want to check, have your alignments all set up, the whole nine.

HOWEVER, you will still have to stick the part on the machine and verify it runs through correctly before you can consider it a "finished" part.
9/10 times, even IF you create a perfectly good, working program, first try, you'll have to adjust the focus, lighting, and filtering, as this is impossible without prior knowledge of how the camera will "see" the part.

It's not so much different from using a touch probe, once you get around the fact that there's not a physical tip.
Get everything programmed on your DXF as best as you can, chuck it in the CMM and hope for the best. (Obviously, run it slow first!)

As mentioned above, you will need a manual alignment in the beginning to tell the machine where the part is. From there, using the DXF nominals, it should be able to take points/scans effectively