Quality tree

A quality tree, also called a quality attribute utility tree, is a hierarchical model that decomposes a system’s overall software quality into successively refined branches. Top-level quality attributes are refined into more specific sub-characteristics, which are themselves broken down further, down to concrete scenarios at the leaves.

Standards for product quality, such as ISO/IEC 25010, propose a generic quality tree applicable to any software product, defining characteristics like reliability, performance efficiency, and maintainability, and their sub-characteristics. The quality tree for a specific system narrows this generic model down to the quality requirements that actually matter for that system, prioritized against its own context and stakeholders.

Because its leaves are concrete and testable, a quality tree is a useful tool in architecture evaluation methods, such as the Architecture Tradeoff Analysis Method (ATAM), where the tree structures discussion of trade-offs among competing qualities.