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[[meta copyright="Copyright © 2007 Free Software Foundation, Inc."]]
[[meta license="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
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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]].
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