It is a specific Goal modeling method; another is i*.
[1] KAOS stands for Knowledge Acquisition in automated specification[2] or Keep All Objectives Satisfied.
[3] The University of Oregon and the University of Louvain (Belgium) designed the KAOS methodology in 1990 by Axel van Lamsweerde and others.
[4] It is taught worldwide at the university level[5] for capturing software requirements.
There is lack of evidence that KAOS is used in the industry[6] and as of February 2023, the only tool supporting it is Objectiver, written by the same group[7] behind the KAOS methodology, with the latest release 3.0c47 dated at March 9th, 2012.