Identifying the body responsible for ensuring that a requirement is met.
Those responsible for creating ICT should usually be able to ascertain whether or not an accessibility requirement that relates to functionality that they provide has met. They can, and often will, declare how such requirements are met by declaring it in a Voluntary Product Accessibility Template (VPAT).
Third-party testers should also be able to ascertain whether an accessibility requirement has been met in most cases. However, there are some EN 301 549 requirements that third-party testers will usually be unable to test. For example, the developer of a software program will know whether or not they have met the requirements in clause 11.5 "Interoperability with assistive technology" that relate to whether the software uses platform accessibility services, but third-party testers will typically be unable to directly observe the usage of these accessibility services. It is therefore unreasonable to expect third-party testers to judge whether these clause 11.5 requirements have been met.
Issue #63 highlights that there are two requirements 11.1.3.1.1 "Info and relationships (open functionality)" and 11.4.1.2.1 "Name, role, value (open functionality)" that overlap with several of the requirements in clause 11.5. What is notable is that there is a possibility that third-party testers should in most circumstances be able to directly assess whether these two requirements have been met. Issue #63 draws attention to the difficulties in asking third-party testers to report on whether both sets of requirements are met (the writers of the software should be able to so).
There are other cases where only a subset of users is to be able to evaluate whether a requirement has been met. Previous concern has been raised about requirements related to the provision of captioning, and whether the characteristics of the captions are under user control. The ability to answer such questions will depend on whether the person answering is the provider of the captioned content or whether it is the person providing third-party content to users.