How do you evaluate and compare the trade-offs among quality attributes in software design?

1 Identify the stakeholders and their concerns

The first step is to identify who are the stakeholders of the system and what are their concerns or goals regarding the quality attributes. Stakeholders can be internal or external, such as users, customers, developers, testers, managers, regulators, or competitors. Their concerns can be expressed as scenarios, questions, or preferences that reflect their expectations and needs. For example, a user might be concerned about how fast the system responds, how easy it is to use, or how secure it is from unauthorized access.

2 Define the quality attributes and their metrics

The next step is to define the quality attributes and their metrics that are relevant for the system and the stakeholders. Quality attributes are the properties or characteristics of the system that affect its behavior or performance, such as availability, reliability, security, usability, scalability, and maintainability. Metrics are the measurable or observable indicators that quantify the degree or level of the quality attributes, such as response time, error rate, throughput, user satisfaction, or defect density. You can use standard definitions and metrics from existing frameworks, such as ISO/IEC 25010, or customize them according to your context and domain.

3 Prioritize the quality attributes and their metrics

The third step is to prioritize the quality attributes and their metrics according to their importance and impact for the system and the stakeholders. You can use various techniques to rank or rate the quality attributes and their metrics, such as surveys, interviews, workshops, voting, or pairwise comparison. You can also use tools or methods to visualize or quantify the priorities, such as quality attribute utility trees, weighted scoring, or analytic hierarchy process. The result of this step is a prioritized list of quality attributes and their metrics that guide your design decisions.

5 Balance the quality attributes and their metrics

The fifth step is to balance the quality attributes and their metrics to achieve a satisfactory level of quality for the system and the stakeholders. Balancing means finding the optimal or acceptable trade-offs among the quality attributes and their metrics that meet the requirements and expectations of the stakeholders. You can use various techniques to balance the quality attributes and their metrics, such as design patterns, tactics, strategies, or principles. You can also use tools or methods to evaluate or compare the alternative design solutions, such as prototypes, simulations, experiments, or benchmarks. The result of this step is a refined and validated design solution that satisfies the quality attributes and their metrics.

6 Document and communicate the quality attributes and their metrics

The sixth and final step is to document and communicate the quality attributes and their metrics to the stakeholders and the developers. Documentation means capturing and recording the quality attributes and their metrics and their rationale, assumptions, dependencies, and trade-offs in a clear and consistent way. Communication means sharing and discussing the quality attributes and their metrics and their implications, risks, and opportunities with the stakeholders and the developers. You can use various formats and media to document and communicate the quality attributes and their metrics, such as quality attribute specification documents, quality attribute models, diagrams, reports, presentations, or reviews. The result of this step is a transparent and traceable design solution that aligns with the stakeholder concerns and goals.

7 Here’s what else to consider

This is a space to share examples, stories, or insights that don’t fit into any of the previous sections. What else would you like to add?