The SEI approach using model-based engineering permits error modeling on an architecture specification early and often throughout the development life cycle. These error models capture the results of failure modes and effects analysis (FMEA) and hazard analysis.
System designers know that software faults may cause failure in many forms, from loss of life and equipment to loss of specific functionality, which hinders mission effectiveness. So, they want to ascertain and demonstrate a level of confidence in the system, expressed perhaps in an availability measure such as a mean time between failures (MTBF) number.
But can they predict how a system will perform when migrated to complex, new environments—such as an integrated modular avionics (IMA) architecture? In an IMA architecture, dedicated processors are replaced by virtual machines in a partitioned environment that can run applications concurrently.
Or, can they gain insight into how choices made to improve reliability affect other critical qualities of the architecture, such as latency, CPU and bus utilization, and scheduling? Can they systematically evaluate each change prior to system integration and test?
Using model-based engineering tools, methods, and techniques the SEI has developed an approach for dependency analysis that applies fault and repair models to system architecture. This approach
The SEI provides technical assistance and guidance to transform the architectural design process from one based on human evaluation to one based on automated analysis.
This analysis includes
Analysis of a system architecture model offers a better way to predict the behavior of quality attributes. The SEI approach to model-based engineering allows analysis
|Reliability Analysis Concern||SEI Approach||SEI Answer|
|Fault tolerance||YES||Error modeling captures FMEA results|
|Availability||YES||Error modeling supports fault tree analysis and MTBF|
|Hazard identification/risk analysis||YES||Designer can evaluate effects of partitioning and assess how other quality attributes might be affected (such as in end-to-end latency)|
The SEI uses the Architecture Analysis and Design Language (AADL) to document a system architecture and provide a platform for multiple analyses. AADL, an international industry standard, supports multiple analyses from a single architectural model, enables modeling and analysis throughout the life cycle, and provides analysis of runtime behavior such as availability, performance, and security.
The AADL error model annex supports mixed-fidelity modeling that makes it easier to modify architecture specifications and automatically regenerate reliability models at different levels of fidelity. The annex also enables improved traceability between architecture specifications and the generated models and analysis results.
The SEI offers the Open Source AADL Tool Environment (OSATE) set of analysis plug-ins for use with AADL models. The OSATE error model plug-in implements the AADL error model annex. This SEI-developed plug-in includes
AADL also can be used with
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