Corresponding to the targets of the SnT interdisciplinary research centre for Security, Reliability and Trust, the SCE Reliability Focus is on interconnected information and communication technology in complex technical environments. It is especially coping with uncertainty due to varying physical properties, disturbances, non-perfect implementation with typical several errors per kilo-line throughout all code involved, and generally limited knowledge about partsystems. It addresses that, with its rising share of value creation and complexity, also failures are increasingly related to software functionality.

The technology cultures in informatics and engineering basicly differ in their approaches of sequential definition versus equational approximation of dynamics. Whereas reliable automata in technical context are established RTD fields. e.g. in mechanical engineering for railway security and in electrical engineering for electricity supply security, information science is developing widely independent. Programs as completely known math-objects, carry the temptation to construct them in a proven correctly way. Weaknesses appear in implementations due to imperfectness of tools, components, and interactivity models. Hence, reliable systems engineering focuses at relating design efforts to the achievable quality.

Continuous complexity and discrete complexity are merging in software systems embedded in techno-physical contexts. Further to the use of numeric, graphic and symbolic computing, engineering increasingly profits from informatics' synthesis strengths in creating complex networked functionalities, e.g. in large-scale open software projects, using advanced configuration/compatibility tools, interface wrapping, middleware etc. Complexity management in the engineering culture has its strengths in analysis of and dealing with uncertainties due to tolerances of dimensions and dynamics, in compensation of disturbances and in design robustness against bounded property variations, failures and bugs.

In logical as well as in continuous realtime computing, interconnected dynamics demand for design that ensures coupled stability and overall dynamic properties against

• structure variations, e.g. by component failure in powergrid-configurations (extrasystem)
• unknown partsystem structure/order (intrasystem)