MSAQM: A Quality Model for Mixed-Source Architecture Evaluation

Software architecture quality evaluation is an important means of assessing architectural soundness and informing the design, maintenance, and evolution of complex software systems. However, existing architecture quality evaluation approaches are largely source-agnostic, and mixed-source-specific quality concerns remain underexplored in architecture quality evaluation. They do not explicitly capture the source-related quality concerns introduced by the coexistence of autonomous and reused code. In mixed-source architectures, autonomous and reused entities often differ in how they are organized, evolved, and constrained, giving rise to concerns related to source interweaving, reduced dependency autonomy, and license-induced architectural constraints. As a result, architectures with substantially different mixed-source configurations may still receive similar quality evaluation results under source-agnostic methods. To address this limitation, we propose MSAQM, a mixed-source architecture quality model that introduces explicit source awareness into architecture evaluation. MSAQM formalizes mixed-source-specific quality concerns through three complementary attributes: Source Interweaving Degree (SID), Path Source Interference (PSI), and License Constraint Severity (LCS). Rather than replacing existing evaluators, MSAQM is designed as a plug-in layer that enhances them with mixed-source awareness while preserving their original general architecture quality evaluation capabilities. We evaluate MSAQM on representative mixed-source architecture changes. The results show that MSAQM improves the ability of existing evaluators to capture mixed-source-specific architecture quality changes while maintaining high consistency with their original assessment behavior.