olemus
talitlusreeglite realiseerimise kiht tarkvara arhitektuuris
= an intermediary for data exchange between the presentation layer and the data access layer in software architecture

ülevaateid
https://objcsharp.wordpress.com/2013/07/22/what-is-a-business-logic-layer-anyway/
https://www.thinkmind.org/download.php?articleid=icsea_2015_4_10_10012
http://cdn.ttgtmedia.com/searchVB/downloads/doingobjectsinVB_ch05.pdf