Brittleness Analysis Of Software Architecture Based On Complex Networks

The complex systems exist widely in the nature and the societies,which have some characteristics such as numerous nodes,complicated relationships and the evolving of its architecture.As a means of the abstract representation of the complex systems,the complex networks play an important role in the study of the complex systems.During its evolvement,the complex networks will occur cascading failures even collapse because of one or some of their components or subsystems' s dysfunctions,which reflect the brittleness of the complex systems.The brittleness is a nature of the complex systems which will not disappear in the evolvement of the systems or under the external factors.This paper will combine the notion of complex systems,complex networks and the brittleness into the study of the software architecture(SA),give an analysis of its complexity and find out the brittleness points which could cause the cascading faiures and lead to the collapse of the whole system.More precisely,major focuses and innovation points of this dissertation are listed below:It is the first time that the software systems are treated as complex systems and the notion of brittleness is put into the study of the collapse of the software system.Give an experiment on a specific software architecture based on ant colony algorithm,and find out the maximum collapse path and the average path length.The "Pipes and Filters" software architecture is chosen as the object of research,the definition of the brittleness path,the Hamilton path are also given.The specific software architecture is transformed to the corresponding complex netwrok in order to give a further look at the relationships of the components of the software systems.Through the ant colony algorithm,the maximum collapse path,the average length and some other statistics are calculated.Finally,the algorithm is proved to be robust to get the statistics when some parameters are changed.Give an analysis to the system characteristics of the evolving complex networks,measure the cascading failures and find out the brittleness points.With ASCAIDA,which were composed of 122 evolving complex networks,the abnormal graphs can be found with the notion of entropy in the information field,then to the abnormal graphs,based on the node centrality,we managed to find out the brittleness points by iteratively removing the nodes with the most degrees and comparing the size of the most connected clusters and the number of the remaining links with the help of GROD(Gradually Remove Outlier Detection)algorithm.Extend the object of study to more larger complex networks,and give an analysis of the system characteristics and its brittlenss from different perspective of view.Having chosen the AS-Oregon as the object and with the singular value decomposition,we selected the trace of the adjacency matrix of the corresponding network of the complex system as a measurement of the system characteristics.We have also chosen the centrality,which includes the degree centrality,the betweenness centrality and the k-shell to measure the brittleness.The experiment showed that the k-shell played a more important role in measuring the brittleness of the complex systems.The cascading failure model of the software architecture(CFMo SA)is proposed,through which the reason and the mechanism of the failures will be clearly showed and it can give good directions to the design and maintenance of the software systems;the complexity research framework of SA(CRFo SA)is also introduced,which includes the brittleness description language of the software system,the evolvement of the software architecture,the definition of the synchromous control in software systems and etc.The framework is aimed to provide a comprehensive platform in the research of the brittleness of the software systems and lay a foundation for the study of the brittleness of SA.Give a comprehensive of the researches on the percolation in recent years.The theory of percolation and explosive percolation can be used to explain the cascading failures,the collapse of the complex systems during its operation and helps to analyse the brittleness of the software system.Different models of percolation and explosive percolation are concluded,including the ER model,the BFW model,the first order phase transition and the second order phase transition induced by the percolation and the continuity of the phase transition are introduced,finally the application of the percolation in reality is discussed.