AADL Sample Clauses

AADL. Architecture Analysis & Design Language (AADL) [7] is a language developed by the Society of Automotive Engineers (SAE), which is designed for the specification, analysis, and automated integration of real-time performance-critical (timing, safety, schedulability, fault tolerant, security, etc.) distributed computer systems. It provides a new vehicle to allow analysis of system designs (and system of systems) prior to development and supports a model-based, model-driven development approach throughout the system life cycle. AADL, like its predecessor MetaH, produces language based modeling artefacts. AADL was developed as a programming language not only to define the textual representation of software architecture but also (and more importantly) to formally define the syntax and semantics. Moreover, AADL permits textual and graphical system representation. The key specification elements of AADL are summarized in Figure 4 [8]. In AADL, components are defined through type and implementation declarations. A Component Type declaration defines a component’s interface elements and externally observable attributes (i.e., features that are interaction points with other components, flow specifications, and internal property values). A Component Implementation declaration defines a component’s internal structure in terms of subcomponents, subcomponent connections, subprogram call sequences, modes, flow implementations, and properties. Components are grouped into application software, execution platform, and composite categories. Packages enable the organization of AADL elements into named groups. Property Sets and Annex Libraries enable a designer to extend the language and customize an AADL specification to meet project or domain specific requirements. Figure 4: AADL elements [8] XXXX supports the early prediction and analysis of critical system qualities—such as performance, schedulability, and reliability. For example, in specifying and analyzing schedulability, AADL-supported thread components include the predeclared execution property options of periodic, aperiodic (event-driven), background (dispatched once and executed to completion), and sporadic (paced by an upper rate bound) events. These thread characteristics are defined as part of the thread declaration and can be readily analyzed. In [9] EAADL (Extended AADL) is presented, extended approach of AADL for embedded system product lines that allow annotating quality requirements.

AADL. AADL is an architecture description language for embedded and safety critical control systems. The approach has its focus on software and hardware integration. It provides modelling support for software, platform, and implementation design, but does not have inherent language support for other system aspects such as for environment, requirements, and functions. Instead, the AADL relies on external domain specific CASE tools such as Matlab/Simulink and ControlH to cover such aspects. Behaviours in AADL are fundamentally imperative, i.e., based on control flow description and source code modules (e.g., in Ada). The concurrency and timing aspect is supported by multitasking (e.g., preemptive RM scheme) on a platform. XXXX naturally specifies only the non-deterministic behaviour of a thread as a set of subprogram calls. For sophisticated state transition and communication, the behavioural annex is introduced to allow behaviour modelling using the non-deterministic hierarchical automaton. For safety analysis and reliability assessment, the Error Model Annex provides standard annotation for possible errors of the components and their connections in the AADL model. The error models of low-level components typically capture the results of failure modes and effects analysis (FMEA). The system error model is a composition of the error models of its components, derived from the system hierarchy, the interaction error models, and the shared computing platform resources. The system error model reflects error propagation between components based on the component dependencies in the AADL architecture model. It typically captures the results of system hazard analysis (HA). Moreover, the Error Model Annex can also model the risk mitigation methods that improve safety and reliability by specifying how components detect and mitigate errors. The resulting annotated AADL model can then be used as an input to various dependability analysis techniques for fault forecasting during different phases of the development cycle. It also enables an integrated approach that ensures consistency and completeness between hazard analysis and FMEA and the safety and reliability analyses that associate them together. For safety design, AADL/MetaH provides specific language constructs for specifying safety levels, criticalities, fault tolerance, and error handling. There is also a separate error model describing errors and their propagations.