Compliance and regulatory constraints are critical non-functional requirements that define the legal, safety, and operational boundaries within which a system must function. Documenting these is of the highest importance because they are mandatory and non-negotiable. These constraints directly influence fundamental aspects of the system's architecture, data management, security protocols, and user accessibility. Failure to adhere to these requirements can result in severe legal penalties, significant financial loss, and damage to an organization's reputation, making them a primary consideration in the system definition phase.

A. Preferred vendor relationship is a business or procurement preference, not a core technical requirement that defines the system's necessary functions or constraints.

C. Employee training schedule is part of the project's implementation and rollout plan, which is formulated after the system has been designed and built.

D. Office seating arrangements are a logistical or facilities management concern and are entirely unrelated to the technical specifications of a system.

1. University Courseware:

Sommerville, I. (2011). Software Engineering (9th ed.). Pearson. In Chapter 4, "Requirements Engineering," the text classifies requirements, stating, "Non-functional requirements... may be derived from the need to conform to standards or legislation" (p. 86). It emphasizes that these constraints, such as data protection laws, are often more critical than individual functional requirements.

2. Official Vendor Documentation:

HPE Aruba. (2022). Aruba Secure Zero Trust and SASE Validated Solution Guide. In the "Customer Requirements" section, "Security and compliance" is listed as a key requirement category. The guide details how the solution must align with corporate security policies and external compliance mandates, demonstrating its foundational importance in the design process (p. 11).

3. Peer-reviewed Academic Publications:

Glinz, M. (2007). On Non-Functional Requirements. 15th IEEE International Requirements Engineering Conference (RE'07), pp. 21-26. This paper categorizes non-functional requirements into different kinds, explicitly identifying "legal and regulatory requirements" as a critical type of constraint that the system must adhere to. (DOI: 10.1109/RE.2007.56)