(58) The principle of transparency requires that any information addressed to the public or to the data subject be concise, easily accessible and easy to understand, and that clear and plain language and, additionally, where appropriate, visualisation be used. Such information could be provided in electronic form, for example, when addressed to the public, through a website. This is of particular relevance in situations where the proliferation of actors and the technological complexity of practice make it difficult for the data subject to know and understand whether, by whom and for what purpose personal data relating to him or her are being collected, such as in the case of online advertising. Given that children merit specific protection, any information and communication, where processing is addressed to a child, should be in such a clear and plain language that the child can easily understand.
ISO/IEC 27701, adopted in 2019, added additional ISO/IEC 27002 guidance for PII controllers.
Here is the relevant paragraph to article 12(2) GDPR:
7.3.1 Determining and fulfilling obligations to PII principals
Control
The organization should determine and document their legal, regulatory and business obligations to PII principals related to the processing of their PII and provide the means to meet these obligations.
Implementation guidance
Obligations to PII principals and the means to support them vary from one jurisdiction to another.
The organization should ensure that they provide the appropriate means to meet the obligations to PII principals in an accessible and timely manner. Clear documentation should be provided to the PII principal describing the extent to which the obligations to them are fulfilled and how, along with an up- to-date contact point where they can address their requests.
The contact point should be provided in a similar way to that used to collect PII and consent (e.g. if PII are collected by email or a website, the contact point should be by email or the website, not an alternative such as phone or fax).