Below is a diagram showing the process of retrieving the document-list and the document. Each affinity domain has its own XCA, which again has its own registry and repositories.
When querying for a document-list, the registry is utilized, as it holds the metadata and references to the documents in the repository. When retrieving a document, the repository is used with the ID from the registry.

Diagram 1: Simplified example on a query of document, each XCA is its own affinity domain, and the response for each domain may be different (ie. some domains reject requests from certain GP-roles)