Entries Tagged as 'Architecture '

An Introduction to the Mission Thread Workshop

Architecture , Mission Thread Workshop 2 Comments »

By Mike Gagliardi
Principal Engineer 
Software Solutions Division

Mike GagliardiIn Department of Defense (DoD) programs, cooperation among software and system components is critical. A system of systems (SoS) is used to accomplish a number of missions where cooperation among individual systems is critical to providing (new) capabilities that the systems could not provide. SoS capabilities are a major driver in the architecture of the SoS and selection of constituent systems for the SoS. There are additional critical drivers, however, that must be accounted for in the architecture that significantly impact the behavior of the SoS capabilities, as well as the development and sustainment of the SoS and its constituent systems’ architectures. These additional drivers are the quality attributes, such as performance, availability, scalability, security, usability, testability, safety, training, reusability, interoperability, and maintainability. This blog post, the first in a series, introduces the Mission Thread Workshop (MTW), and describes the role that it plays in assisting SoS programs to elicit and refine end-to-end SoS mission threads augmented with quality attribute considerations.

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AADL: Four Real-World Perspectives

Architecture , Architecture Analysis & Design Language (AADL) No Comments »

By Julien Delange 
Member of the Technical Staff

Julien DelangeMismatched assumptions about hardware, software, and their interactions often result in system problems detected too late in the development lifecycle, which is an expensive and potentially dangerous situation for developers and users of mission- and safety-critical technologies. To address this problem, the Society of Automotive Engineers (SAE) released the aerospace standard AS5506, named theArchitecture Analysis & Design Language (AADL). The AADL standard,defines a modeling notation based on a textual and graphic representation used by development organizations to conduct lightweight, rigorous—yet comparatively inexpensive—analyses of critical real-time factors, such as performance, dependability, security, and data integrity. AADL models capture both software and hardware components, as well as their interactions, including the association of a software process on a processor or the deployment of connection on a bus. The AADL standards committee, led by my colleague, Peter Feiler, who played an instrumental role in the development of AADL, meets regularly with members from around the globe who represent a wide variety of industries, from avionics to aerospace, to discuss evolving elements of the standard and to work together on action items from prior standards meetings. In this post, we present highlights from a series of podcasts that we recorded with Feiler and four members of the standards committee discussing their real-word application and experiences with AADL.

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Managing Model Complexity

Architecture , Model-Based Engineering No Comments »

By Julien Delange
Member of the Technical Staff
Software Solutions Division

Julien Delange Over the years, software architects and developers have designed many methods and metrics to evaluate software complexity and its impact on quality attributes, such as maintainability, quality, and performance. Existing studies and experiences have shown that highly complex systems are harder to understand, maintain, and upgrade. Managing software complexity is therefore useful, especially for software that must be maintained for many years. To generate the complexity metrics, tools extract applicable data—such as source lines of code, cohesion, coupling, and more—from binary or source code to analyze the software and report its complexity and quality. Several tools support these techniques and help stakeholders manage the evolution of system development, provide quality improvements, prevent lack of cohesion, and perform other tasks. To date, such approaches have been successfully used in many projects, but as system development moves toward model-based engineering, these methods, metrics, and tools might not be sufficient to manage model complexity. This blog post details the state of the art for reporting model complexity and introduces research underway at the SEI in this area.

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Code Generation with AADL: A State-of-the-Art Report

Architecture , Architecture Analysis & Design Language (AADL) No Comments »

By Julien Delange 
Member of the Technical Staff
Software Solutions Division

Dr. Julien DelangeGiven that up to 70 percent of system errors are introduced during the design phase, stakeholders need a modeling language that will ensure both requirements enforcement during the development process and the correct implementation of these requirements. Previous work demonstrates that using the Architecture Analysis & Design Language (AADL) early in the development process not only helps detect design errors before implementation, but also supports implementation efforts and produces high-quality code. Our latest blog posts anda recent webinar have shown how AADL can identify potential design errors and avoid propagating them through the development process. Verified specifications, however, are still implemented manually. This manual process is labor intensive and error prone, and it introduces errors that might break previously verified assumptions and requirements. For these reasons, code production should be automated to preserve system specifications throughout the development process. This blog post summarizes different perspectives on research related to code generation from architecture models. 

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Evolutionary Improvements of Quality Attributes: Performance in Practice

Agile , Architecture , Architecture Tradeoff Analysis Method (ATAM) , Quality Attribute Workshop No Comments »

By Neil Ernst 
Member of the Technical Staff 
Software Solutions Division

This post is co-authored by Stephany Bellomo

Neil ErnstContinuous delivery practices, popularized in Jez Humble’s 2010 bookContinuous Delivery, enable rapid and reliable software system deployment by emphasizing the need for automated testing and building, as well as closer cooperation between developers and delivery teams. As part of the Carnegie Mellon University Software Engineering Institute's (SEI) focus on Agile software development, we have been researching ways to incorporate quality attributes into the short iterations common to Agile development. We know from existing SEI work on Attribute-Driven DesignQuality Attribute Workshops, and the Architecture Tradeoff Analysis Method that a focus on quality attributes prevents costly rework. Such a long-term perspective, however, can be hard to maintain in a high-tempo, Agile delivery model, which is why the SEI continues to recommend an architecture-centric engineering approach, regardless of the software methodology chosen. As part of our work in value-driven incremental delivery, we conducted exploratory interviews with teams in these high-tempo environments to characterize how they managed architectural quality attribute requirements (QARs). These requirements—such as performance, security, and availability—have a profound impact on system architecture and design, yet are often hard to divide, or slice, into the iteration-sized user stories common to iterative and incremental development. This difficulty typically exists because some attributes, such as performance, touch multiple parts of the system. This blog post summarizes the results of our research on slicing (refining) performance in two production software systems. We also examined the ratcheting (periodic increase of a specific response measure) of scenario components to allocate QAR work.

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