Which of the following is not an IREB validation quality criteria for specification content?

The validation quality criteria for specification content as defined by the IREB are essential for ensuring that requirements are clearly defined and can be reliably used in software development. Among these criteria are verifiability, necessity, and completeness of the document, each playing a significant role in the quality of requirements.

Verifiability ensures that the requirements can be tested or measured to confirm that they are met. Necessity refers to the idea that each requirement is essential for the system being developed, meaning that it should deliver value and not just be included without purpose. Completeness of the document indicates the need for the specification to cover all necessary aspects without leaving gaps that could lead to misinterpretations or incomplete implementations.

Understandability, while an important attribute of effective communication, is not strictly categorized as one of the validation quality criteria by IREB. It focuses more on how easily the requirements can be comprehended by stakeholders rather than their quality in terms of technical specifications or testing. Therefore, the correct choice highlights that understandability, although important, does not fit within the specific framework of IREB verification criteria.