Hello Eloisa, Gwyneth, Erik,
as you've noticed, QLM implements various measures of a surface spin (some better tested than others). Unfortunately the references to the corresponding formalisms are scattered around, but here's a primer:
This information seems to be missing from the thorn documentation. Would it be possible to add it (even the primer that Eliosa provided) to it? Either directly for those that have commit rights or as a pull request on bitbucket?
Yours, Roland