A requirements architecture is a collection of views that represent the requirements from different perspectives and levels of abstraction. A requirements architecture helps to assess the completeness and coherence of the requirements, as well as to identify any gaps, overlaps, or inconsistencies among the requirements. A requirements architecture also helps to communicate the requirements to different stakeholders and to facilitate the solution design and testing. A requirements architecture is different from a requirements traceability matrix, which is a tool that shows the relationship between requirements and other artifacts, such as test cases, design elements, or business objectives; a business knowledge model, which is a representation of the business concepts, rules, and relationships that are relevant to the business need or the solution; and a solution design, which is a description of how the solution will meet the requirements and deliver the expected value.
References:
CCBA Handbook, page 18
[BABOK Guide], page 54
[Business Analysis for Practitioners: A Practice Guide], page 63
[Business Analysis: The Question and Answer Book], page 30