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diff --git a/hurd/ng/designprinciples.mdwn b/hurd/ng/designprinciples.mdwn new file mode 100644 index 00000000..42faa52f --- /dev/null +++ b/hurd/ng/designprinciples.mdwn @@ -0,0 +1,39 @@ +# <a name="Design_Principles"> Design Principles </a> + +A design principle is a test that lets us **reject** things. Hopefully, when combined with other design principles, it forms a basis for making coherent and consistent decisions about design goals and system features. [1] + +## <a name="Stated_design_principles"> Stated design principles </a> + +None defined yet, but there seems to be consensus that ngHurd should be a principle-driven design. + +## <a name="Potential_design_principles"> Potential design principles </a> + +Here is an incomplete list of potential design principles for the ngHurd. It is taken from [2]. I left out some principles I think do not apply or are not in question. Feel free to add more. + +### <a name="Principles_from_the_Multics_Proj"> Principles from the Multics Project </a> + +* _Economy of mechanism_: Keep the design as simple as possible. +* _Fail-safe defaults_: Base access decisions on permission rather than exclusion. +* _Least priviledge_: Components should have no more authority than they require. +* _Least common mechanism_: Minimize the amount of shared instances in the system. + +### <a name="Commonly_accepted_principles"> Commonly accepted principles </a> + +* _Separation of policy and mechanism_ +* _Least astonishment (also known as principle of least surprise):_ The system�s behavior should match what is naively expected. +* _Complete accountability_: All real resources held by an application must come from some accounted pool. +* _Safe restart_: On restart, the system must either already have, or be able to rapidly establish, a consistent and secure execution state. +* _Reproducibility_: Correct operations should produce identical results regardless of workload. + +### <a name="Principles_specific_to_EROS"> </a> Principles specific to EROS + +* _Credible policy_: If a security policy cannot be implemented by correct application of the system�s protection mechanisms, do not claim to enforce it. +* _Explicit authority designation_: Every operation that uses authority should explicitely designate the source of the authority it is using. +* _Relinquishable authority_: If an application holds some authority, it should be able to voluntarily reduce this authority. + +---- + +See also: + +* [1] <http://lists.gnu.org/archive/html/l4-hurd/2005-11/msg00120.html> +* [2] EROS: A Principle-Driven Operating System from the Ground Up |