Context.In the context of Software Architecture, AADL (ArchitectureAnalysis and Design Language) is one of the latest standards (SAE StandardAS5506) used for analyzing and designing of architectures of software sys-tems. Dependability evaluation of an avionic system, modeled in AADL, isconducted using petri nets standard PNML (ISO standard ISO/IEC15909-2).A maintainability analysis of PNML dependability model is also con-ducted.

Objectives. In this study we investigate maintainability analysis of PNMLdependability model of an avionic system designed in AADL. Structural,functional, fault-tolerance and recovery dependencies are modeled, imple-mented, simulated and validated in PNML. Maintainability analysis withrespect to ‘changeability’ factor is also conducted.

Methods.This study is a semi-combination of ’case-study’ and ’implemen-tation’ research methodologies. The implementation of case-study systemis conducted by modeling the case-study system in AADL using OSATE2tool and simulating the dependability models in PNML using Wolfgangtool. PNML dependability models are validated by comparing with GSPNdependability models of previously published research.

Results. As a result of this research, PNML dependability model was ob-tained. The difficulties that influenced the research in AADL Error ModelAnnex and the OSATE2 tool are also analyzed and documented. PNMLand GSPN are compared for complexity. And maintainability analysis forPNML dependability model w.r.t ‘changeability’ factor is also an outcomeof this research. This research is recommended for software testing at ar-chitecture level as a standardized way for testing the software componentsfor faults and errors and their impact on dependable components.

Conclusions. We conclude that PNML is an ISO standard and is the al-ternative for GSPN for dependability. Also, AADL Error Model Annex isstill evolving and there is a need of availability of proper literature publiclyfor better understanding. Also, PNML dependability model possesses the‘changeability’ factor of maintainability analysis and therefore it is able toadapt changes in the architecture. Also, dependability factors of a softwarecan be tested at architecture level using the standards; AADL and PNML