What is an association of organizations that come together to exchange appropriate information about their users and resources called?

The correct choice is federation, which refers to an association of organizations that collaborate to share information about their users and resources while maintaining individual autonomy and control over their respective domains. In a federation, organizations establish a framework for trust, allowing them to exchange data and facilitate authenticated access across different systems or platforms. This is particularly important in scenarios involving single sign-on (SSO), where users can access multiple services without the need to repeatedly log in, streamlining the user experience.

Federations enable organizations to leverage each other's identity management systems, enhancing security and efficiency while reducing the complexity that would arise if each organization operated entirely independently. This concept is fundamental in cloud computing and various enterprise applications where collaborative data exchange is necessary.

In contrast, an identity repository is primarily a storage solution for user identities and credentials, which lacks the collaborative aspect of a federation. DAST (Dynamic Application Security Testing) is a method for identifying security vulnerabilities in applications under real-world attack conditions, and ONF (Open Networking Foundation) is related to network architecture standards rather than data sharing among organizations.