Cfengine, or the "configuration engine" is a very high level language
for building expert systems which administrate and configure large
computer networks. Cfengine uses the idea of classes and a primitive
form of intelligence to define and automate the configuration of
large systems in the most economical way possible. Cfengine is
designed to be a part of computer immune system.

Cfengine 3 is operationally backwards compatible with Cfengine 2, but the
language is not. Cfengine 3 is not a drop-in replacement for Cfengine 2.