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Enabling Incremental Iterative Development at Scale: Quality Attribute Refinement and Allocation in Practice

June 2015 Technical Report
Neil Ernst, Stephany Bellomo, Robert Nord, Ipek Ozkaya

This report describes industry practices used to develop business capabilities and suggests approaches to enable large-scale iterative development, or agile at scale.


Software Engineering Institute

CMU/SEI Report Number



Lengthy requirements, design, integration, test, and assurance cycles delay delivery, resulting in late discovery of mismatched assumptions and system-level rework. In response, development methods that enable frequent iterations with small increments of functionality, such as agile practices, have become popular. But such methods de-emphasize architectural analysis; they assume the emergence or existence of a stable architecture. Yet as the business goals and context evolve, the architecture must also change, which requires allocating increments of quality attribute requirements to iterations along with other business capabilities. Quality attribute requirements (also called nonfunctional requirements) are hard to separate into smaller increments since they often crosscut many aspects of the product. As a result, allocation is uneven since it is challenging to decompose them and understand their value. Working with quality attribute requirements in an incremental and iterative fashion involves solving two problems: separating high-level requirements into their constituent parts and allocating them to iterations to fulfill the requirement. Underpinning both problems is the need for measurements to show that the requirement is satisfied. This report describes industry principles and practices used to smooth the development of business capabilities and suggests some approaches to enabling large-scale iterative development, or “agile at scale.”