[[!meta copyright="Copyright © 2007, 2008 Free Software Foundation, Inc."]] [[!meta license="""[[!toggle id="license" text="GFDL 1.2+"]][[!toggleable id="license" text="Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.2 or any later version published by the Free Software Foundation; with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. A copy of the license is included in the section entitled [[GNU Free Documentation License|/fdl]]."]]"""]] The Collaborative International Dictionary of English v.0.48 defines a mechanism as: > The series of causal relations that operate to produce an > effect in any system; as, the mechanism of a chemical > reaction. This is, a mechanism is a function that produces some result. As mechanisms determine the type of result, they necessarily impose some [[policy]] (rules). Mechanisms that are referred to as policy-free are those that minimally impose policy. A process can be used to encapsulate a program instance. On [[Unix]], a process is associated with a UID. This UID, in part, determines what the process is authorized to do. On a [[microkernel]], the policy that controls what resources a process may access are realized separately. This may achieved through the use of UIDs, however need not. Thus, the processes mechanism on such microkernels impose less policy than on Unix. A process is not policy free as it is possible to use other mechanisms to encapsulate a program instance, e.g., [[SFI]] and tainting ala [[Asbestos]].