Can the SwiftUI document architecture Take a file as read-only; never to be written out Take files too large for memory (multi-MB, or even GB) I wouldn't want the system to read a gigabyte size file into memory by default. If the system can use a memory-mapped Data as the representation, that'll be something I can make do. It would be even better if I could tell the system that I'll handle all the reading, all I need from it is a reference to the file's location on disk.

Instead of a .sdef file (or older formats) made in advance and stored in an app’s bundle, I wonder if the script dictionary can be set soon after the app opens? I seen related API, with a note that the scripting file reader ultimately calls that API. I grok about 90% of that API, but I’m not sure it’s possible.