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<p>New page: This page contains the basic principles and properties in applied system theory relevant to build distributed and complex applications. Many of the basic principles in applied system the...</p> <p><b>New page</b></p><div>This page contains the basic principles and properties in <br /> applied system theory relevant to build distributed and complex <br /> applications. Many of the basic principles in applied system theory are<br /> at the same time also the basic problems in many<br /> [[Distributed System|distributed systems]]:<br /> <br /> * [[Availability]] - an application is able to run 24/7 (non-stop 24 hours per day and seven days a week)<br /> * [[Fault Tolerance]], [[Failover]] - an application is able to handle faults and errors gracefully<br /> * [[Flexibility]] - an application is able to react to changes<br /> * [[Robustness]] - an application can function in the presence of pertubations: faults, failures or adverse conditions<br /> * [[Scalability]] - an application can scale up and down to match demand<br /> <br /> For large-scale system which are very complex or very distributed <br /> these properties are of course desirable, but not easy to achieve.<br /> Many [[Self-Organization|self-organizing systems]] that can be <br /> observed in nature seem to be [[Fault Tolerance|fault tolerant]], <br /> [[Scalability|scaleable]], [[Robustness|robust]] and [[Adaptation|adaptive]]. Unfortunately, <br /> these systems in nature have also drawbacks, they are more or less unpredictable, <br /> unreliable, and uncertain as well (and sometimes even incomprehensible <br /> due to their high [[Complexity|complexity]]).<br /> <br /> The main characteristics of natural [[Self-Organization|self-organizing systems]]<br /> are [[Autonomy|autonomy]] and [[Redundancy|redundancy]] - they are made of many redundant <br /> agents or actors. Such systems have usually many different <br /> [[Self-Star Properties|Self-* Properties]], they can heal <br /> and protect themselves and recover automatically.<br /> Therefore the above properties are typically tried to achieved with the help of <br /> * [[Redundancy]] and [[Replication]]<br /> * [[Self-Star Properties|Self-* Properties]], esp. self-management<br /> * Automated [[Recovery]]<br /> <br /> One obvious way to achieve fault-tolerance and scalability is to design for <br /> failure and for scalability, that is expect failures and increasing workload at <br /> any time. In general the design of desirable system properties like [[Robustness|robustness]],<br /> [[Fault Tolerance|fault tolerance]] and [[Scalability|scalability]] seems currently<br /> to be an art.<br /> <br /> [[Category:Applied Principles]]</div>

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