Heuristics to Perform Molecular Decomposition of Large Mission-Critical Information Systems

The molecular approach has been introduced at the beginning of the Deserec project to decrease the complexity of managing large mission-critical information systems. Actually it consists in a meta-model based on the fact that gathering relevant information systems components together into molecules makes the administration of such complex systems easier. On the one hand, a global and synthetic view of the system is provided. No needs for entering technical details to understand the global situation assess the risks, and decide a reconfiguration. On the other hand, the molecule view simplifies the simulation of the system behavior and its vulnerability analysis. Obviously, such a modeling necessarily implies approximations in the computation of performance or dependability metrics. Thatpsilas the reason why it turns out that it is essential to clearly depict the principles and the rules that lead the system administrator to a given molecule breakdown. Next to these cutting-up rules we'll try to identify relevant metrics for each type of molecule so that reconfigurations decisions may be taken at the molecule level.This paper intends to first recall the key principles of the molecule approach and then give rules and principles on how to address the system decomposition in a safe and efficient way.