James Antognini wrote the Subsystem Interface paper presented at SHARE 61 that I used to build ADS Tape Protection. I implemented my subsystem as as system address space; when I found out that Antognini was going to talk about this technique, I had to attend it just to keep him honest.
The Score: Andrews - 1, Antognini - 1. He was wrong about FORCE-ability and CANCEL-ability as far as data-only address spaces were concerned. I was wrong about the presence of a JSCB. I demand a rematch!
Antognini talked about another technique that I didn't know about; I was under the impression that I couldn't do I/O from a system address space without faking certain scheduler control blocks. Turns out that you can get a system service to give you access to all the datasets represented in the MSTRJCL. Hmmm. Might be a way for me to get rid of one of my external batch utilities and integrate it with the subsystem address space. Hmmm.