x1 is a message/notice/memorandum about subject x2 from author x3 to intended audience x4.
Emphasis on brevity, single or identifiable subject (contrast with xatra: the emphasis in notci is on the single or cohesively focused subject, while the audience is less defined - indeed only an 'intended' audience. xatra need not have a single or focussed subject - its corresponding place is for 'content'); reminder/memo/note (= mojnoi). See also xatra, nuzba, mrilu, morji.