$ U \meet W $ is a natural companion of $ U \sub W $ being its logical dual
(recall that $ U \sub W $ means $ (\lall u \in U)\ u \in W $)
and is already being used successfully in the context of a constructive
({\ie} intuitionistic and predicative) approach to point-free topology
\cite{Sam00}.
$ U \meet W $ is a natural companion of $ U \sub W $ being its logical dual
(recall that $ U \sub W $ means $ (\lall u \in U)\ u \in W $)
and is already being used successfully in the context of a constructive
({\ie} intuitionistic and predicative) approach to point-free topology
\cite{Sam00}.