On 06/02/2025 09:02 GMT Denny Vrandečić dvrandecic@wikimedia.org wrote:
News in Types: Kleenean
In order to get back into creating more Types, we have kicked the year off with implementing the Type proposal for Kleenean values https://www.wikifunctions.org/wiki/Wikifunctions:Type_proposals/Kleenean. This is used to represent values for a three-valued logic https://en.wikipedia.org/wiki/Three-valued_logic#Kleene_and_Priest_logics. Unlike Boolean logic, which has two values (True and False), the Kleenean logic has three values: True, False, and Maybe.
I do find this interesting, from the rather arcane-seeming angle of implication for the Kleenean values (aka lifted Booleans). There appear to be two different versions of "maybe" implication. Back in 2017, as a Wikimedian in Residence, I wrote a blogpost attempting to explain one of those in operational terms:
https://moore.libraries.cam.ac.uk/meet-your-wikimedian-residence/unknown
Charles