olemus
formaalloogika haru, mis
kasutab modaalsust väljendavaid operaatoreid,
laiendades klassikalist lause- ja predikaatarvutust
modaaloperaatorite ehk modaalsustega

Wiktionary:
(logic) any formal system that attempts to deal with modalities, such as possibility and necessity, but also obligation and permission

ülevaateid
https://plato.stanford.edu/entries/logic-modal/

http://www.iep.utm.edu/modal-lo/

http://web.cecs.pdx.edu/~mperkows/PERKOWSKI_PRESENTATIONS/Perkowski.Seminar.SySc.2011.pdf

https://en.wikipedia.org/wiki/Modal_logic

https://en.wikipedia.org/wiki/Category:Modal_logic

turvarakendusi
https://www.eeict.cz/eeict_download/archiv/sborniky/EEICT_2006_sbornik/03-Doktorske_projekty/07-Informacni_systemy/10-xocena01.pdf

http://www.di.unito.it/~guido/alfieri/aucher-elal10b.pdf

http://dl.ifip.org/db/conf/forte/forte2007/Chae07.pdf

https://people.mpi-sws.org/~dg/papers/stm11-aclnew.pdf

https://eprint.iacr.org/2006/262.pdf

http://owncloud.unsri.ac.id/journal/security/logical_sec_policie.pdf