Formalization of the structural complexity of software as a factor in the design assessment of its reliability

This study is devoted to one aspect of designing automated control systems for water transport facilities, such as logistics centers, container terminals, ports, ship repair yards, shipping companies, and lock navigation channels on regulated inland waterways. The problem of developing a methodology for the quantitative design assessment of the structural complexity of software under development is considered, since this complexity is a significant factor in assessing its reliability, and increasing complexity inevitably leads to various types of vulnerabilities in program code. A set of factors on which structural complexity depends is defined. A corresponding set of terms is introduced to designate these factors assuming the use of a modular development principle: module call spectrum, module alternative spectrum, module depth, module cyclicity, weighted module depth, weighted module cyclicity. The expediency of transitioning to the corresponding dimensionless indicators is justified. Building on the previously formulated multiplicative method of aggregating a general system integral indicator from a set of partial indicators, a final formula for the design indicator of structural complexity of automated control system software is provided, and a method for including it in the design assessment of the overall reliability of the control loop is proposed. A metric for vector evaluation of differences in structural complexity among alternative software products is introduced.