> i thought jigsaw was about compilation artifacts.
Nope, jigsaw doesn't affect compilation artifacts other than an additional module-info.class present in a .jar file.
There is an intentionally completely unspecified, Oracle/OpenJDK proprietary extension (yes) called jlink that generates different artifacts. The aritfacts are unspecified, only work with Oracle/OpenJDK, and the licensing restrictions for redistribution are unclear.
> are you saying there are is a (nontrivial) runtime component? what does it do?
1. module definitions have to be parsed into memory structures to build a runtime model of the module system
2. the runtime model built in 1. has to be validated
3. every access has to be checked if it is permitted by the module system based on the information from 1.. If it is not permitted a decision has to be taken what should be done, this can include figuring out whether it is the first such access which needs additional memory structures (this is the default). See [1] for more information.
Probably some additional things that I forgot about.
