Robustness - Revision history

Jfromm at 19:00, 1 December 2008

2008-12-01T19:00:35Z

← Older revision		Revision as of 14:00, 1 December 2008
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	Reliability, robustness and [[Fault Tolerance\|fault tolerance]] can be achieved by		Reliability, robustness and [[Fault Tolerance\|fault tolerance]] can be achieved by
	[[Redundancy\|redundancy]] and [[Replication\|replication]].		[[Redundancy\|redundancy]] and [[Replication\|replication]].
			In his paper [http://www.institutnicod.org/Reduction/7.OntComplSys.pdf The Ontology of Complex Systems], William Wimsatt gives the following definition of robustness:

			:''Things are robust if they are accessible (detectable, measureable, derivable, defineable, produceable, or the like) in a variety of independent ways.''

	Basically, a system is robust if a certain operation or process can be achieved		Basically, a system is robust if a certain operation or process can be achieved
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	* diversity of nodes: access different redundant instances of a node		* diversity of nodes: access different redundant instances of a node
	* diversity of design/versions: reach a computational goal in different ways		* diversity of design/versions: reach a computational goal in different ways

	~~In his paper [http://www.institutnicod.org/Reduction/7.OntComplSys.pdf The Ontology of Complex Systems], William Wimsatt gives the following definition of robustness:~~

	~~:''Things are robust if they are accessible (detectable, measureable, derivable, defineable, produceable, or the like) in a variety of independent ways.''~~

	In any case, diversity and [[Redundancy\|redundancy]] are the key. There are in general		In any case, diversity and [[Redundancy\|redundancy]] are the key. There are in general

Jfromm at 18:59, 1 December 2008

2008-12-01T18:59:53Z

← Older revision		Revision as of 13:59, 1 December 2008
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	* diversity of nodes: access different redundant instances of a node		* diversity of nodes: access different redundant instances of a node
	* diversity of design/versions: reach a computational goal in different ways		* diversity of design/versions: reach a computational goal in different ways

			In his paper [http://www.institutnicod.org/Reduction/7.OntComplSys.pdf The Ontology of Complex Systems], William Wimsatt gives the following definition of robustness:

			:''Things are robust if they are accessible (detectable, measureable, derivable, defineable, produceable, or the like) in a variety of independent ways.''

	In any case, diversity and [[Redundancy\|redundancy]] are the key. There are in general		In any case, diversity and [[Redundancy\|redundancy]] are the key. There are in general

Jfromm at 20:50, 2 October 2008

2008-10-02T20:50:09Z

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			::::People err. That is a fact of life. People are not precision machinery designed for accuracy
			::::In fact, we humans are a different kind of device entirely. Creativity, adaptability, and
			::::flexibility are our strengths. Continual alertness and precision in action or memory are our
			::::weaknesses. We are amazingly error tolerant, even when physically damaged. We are extremely
			::::flexible, robust, creative, and superb at finding explanations and meanings from partial and
			::::noisy evidence. The same properties that lead to such robustness and creativity also produce
			::::errors. The natural tendency to interpret partial information -- although often our prime virtue
			:::: -- can cause operators to misinterpret system behavior in such a plausible way that the
			::::misinterpretation can be difficult to discover. - Donald A. Norman


	'''Robustness''' in the context of software systems and applications is defined as the degree		'''Robustness''' in the context of software systems and applications is defined as the degree
	to which a [[System\|system]] or component can still function in the presence of pertubations:		to which a [[System\|system]] or component can still function in the presence of pertubations:

Jfromm: New page: '''Robustness''' in the context of software systems and applications is defined as the degree to which a system or component can still function in the presence of pertubations:...

2008-10-02T20:05:58Z

New page: '''Robustness''' in the context of software systems and applications is defined as the degree to which a system or component can still function in the presence of pertubations:...

New page

'''Robustness''' in the context of software systems and applications is defined as the degree
to which a [[System|system]] or component can still function in the presence of pertubations:
faults, failures or adverse conditions. It is is associated with the resilience of a
system and the ability to maintain function despite adverse (worst case) conditions and
unfavorable changes in internal structure or external environment. A robust system
is "pertubation-resistant".
A system which can stil function in the presence of faults is called [[Fault Tolerance|fault tolerant]].
Robustness depends on the fragility and brittleness of a [[System|system]], and is a measure of
how sensitive a particular system is to changes and disturbances.
Reliability, robustness and [[Fault Tolerance|fault tolerance]] can be achieved by
[[Redundancy|redundancy]] and [[Replication|replication]].

Basically, a system is robust if a certain operation or process can be achieved
in many ways, if '''there are many ways of doing the same thing'''.
For example, there are many different ways to reach a node, because there
is more than one path to it, or there are many different ways to access
a certain node type, because there are many redundant instances.

* diversity of links: reach a node on different paths
* diversity of nodes: access different redundant instances of a node
* diversity of design/versions: reach a computational goal in different ways

In any case, diversity and [[Redundancy|redundancy]] are the key. There are in general
two different ways to increase robustness in [[Distributed System|distributed systems]]:
first [[Redundancy|redundancy]] of components, elements and nodes, and second
[[Redundancy|redundancy]] of paths, links and channels between them.
The former can be found in the [[Replication|replication]] of nodes,
the latter can be observed in the internet, if one route is blocked, then
another is taken. If there is always another way to reach the goal,
then the failure of a single node or link does not affect the function
of the system. A third method to increase robustness and [[Fault Tolerance|fault tolerance]] is
'design diversity' to protect the system against design faults:
the use of multiple functionally equivalent but diverse program versions based
on the same specification to ensure safety in critical applications and to
protect the most vital subsystems of complex systems and networks against design faults
(also known as N-Version Programming or NVP which was first proposed by Algirdas Avizienis
in 1977).

[[Category:Applied Principles]]