Requirements validation is the process of checking that requirements actually define the system that the customer really wants. It overlaps with analysis as it is concerned with finding problems with the requirements. Requirements validation is important because errors in a requirements document can lead to extensive rework costs when these problems are discovered during development or after the system is in service. The cost of fixing a requirements problem by making a system change is usually much greater than repairing design or coding errors. The reason for this is that a change to the requirements usually means that the system design and implementation must also be changed. Furthermore, the system must then be re-tested.
During the requirements validation process, different types of checks should be carried out on the requirements in the requirements document. These checks include:
- （Validity checks）: A user may think that a system is needed to perform certain function. However, further thought and analysis may identify additional or different functions that are required. Systems have diverse stakeholders with different needs and any set of requirements is inevitably a compromise across the stakeholder community.
- （Consistency checks） : Requirements in the document should not conflict. That is, there should not be contradictory constraints or different descriptions of the same system function.
- （Completeness checks） : The requirements document should include requirements that define all functions and the constraints intended by the system user.
- Realism checks: Using knowledge of existing technology, the requirements should be checked to ensure that they can actually be implemented. These checks should also take account of the （budget and schedule） for the system development.
- Verifiability: To reduce the potential for dispute between customer and contractor, system requirements should always be written so that they are verifiable. This means that you should be able to write a set of tests that can demonstrate that the delivered system meets each specified （requirement） .
需求验证是确保需求精准匹配客户真实诉求的关键环节，其核心价值在于大幅降低项目返工成本——需求文档的错误若在开发阶段或系统上线后才发现，修复成本远高于设计、编码阶段的错误，因为需求变更会牵连系统设计、实现及全流程重测。需求验证需开展多维度检查：一是有效性检查，要确认需求真正契合各利益相关方的实际需求，由于系统涉及不同诉求的干系人，需求本质是多方诉求的平衡结果，需避免需求偏离用户真实需要；二是一致性检查，需保障需求文档内无矛盾，同一系统功能的描述、约束不能出现冲突，防止开发方向混乱；三是完整性检查，要确保需求覆盖用户预期的所有功能与约束，无内容遗漏，为开发提供全面指导；四是现实性检查，需结合现有技术能力，同时重点考量项目的预算与时间进度，确保需求在资源限制下具备可落地性；五是可验证性检查，所有需求需具备可验证性，即能通过设计对应测试用例，验证交付系统是否满足需求，这是减少供需方纠纷、保障需求可执行的重要前提。
本题考察的是需求验证（Requirements Validation）的检查方法。
语境定位：原句为 “____ A user may think that a system is needed to perform certain function.”。空后 A user may think that a 是判断本空的关键。
答案判断：从语法看，这里需要名词或名词短语；从语义看，应填“有效性检查，确认需求是否真正反映客户想要的系统”。因此应选 Validity checks。
选项辨析：
A. Security checks：是关于系统安全性的检查，与确认用户真实需求无关。
B. Validity checks：有效性检查用于确认需求是否真正代表了用户的真实需求，符合题干描述，符合语境。
C. Consistency checks：用于发现需求之间是否矛盾，而不是判断用户是否需要，错误。
D. Completeness checks：是检查需求是否完整，与题干描述不符。
因此，选项 B 正确。