Prioritizing Non-Functional Requirements and Influencing Factors for API Quality Framework: An Industry Approach

Application Programming Interface (API) management is currently a trending research area; however, APIs require careful attention to Non-Functional Requirements (NFRs) to ensure system performance, maintainability, security, and resiliency. The software industry struggles to maintain API quality, especially NFRs, due to a focus on functional aspects in standards like the OpenAPI Specification (OAS). Similarly, standards, such as ISO/IEC 25010:2023, evaluate the quality of general software but offer limited guidance on addressing API challenges. Based on the industry perspective, this paper prioritizes the most critical quality attributes and their influencing factors for APIs, supporting the development of a Non-Functional Requirement Quality Framework for APIs (NFRQF-API). We adopted ISO/IEC 25010 as our reference standard and surveyed industry experts. Eleven NFRs are added in the survey, including nine from ISO/IEC 25010 and two additional attributes, Observability and Resiliency, identified through the literature review. A structured survey tool has been validated, pilot-tested, and distributed to 38 API practitioners, with data analyzed through IBM Statistical Package for the Social Sciences (IBM SPSS). SPSS demonstrates strong internal consistency (α > 0.7) across items within each group. Additionally, Maintainability (4.29) and Resiliency (4.20) have been identified as core NFRs, while Interaction Capability (3.18), Flexibility (3.18), and Safety (2.93) have lower scores based on their mean calculation. The remaining six NFRs are moderately significant, highlighting their ongoing importance. These findings, based on NFR classification, establish a solid foundation for developing a Quality Framework for APIs aligned with modern Software engineering requirements. The article supports researchers and practitioners to build a strong understanding towards NFR prioritization, which is a crucial step for API quality management.