Theoretical and empirical validation of software trustworthiness measure based on the decomposition of attributes

From the perspective of attribute decomposition, there are a variety of software trustworthiness metric models. However, little attention has been paid to using more rigorous methods and to performing theoretical validation. Axiomatic methods formalise the empirical understanding of software attributes through defining ideal metric properties. They can offer precise terms for the software attributes' quantification. We have utilised them to assess software trustworthiness on the basis of attribute decomposition, presented four properties, constructed a software trustworthiness measure (STMBDA for short). In this paper, we extend the set of properties, introduce two new properties, namely non-negativity and proportionality, and perfect substitutability and expectability. We verify the theoretical rationality of STMBDA by demonstrating that it conforms to the new property set and the empirical validity by evaluating the trustworthiness of 23 spacecraft software. The validation results show that STMBDA is able to effectively assess the spacecraft software trustworthiness and identify weaknesses in the development process.