DDSSEC12 — Built-in Access Control: interpretation of enable_read/write_access_control

The check_create_participant entry of "Table 63 - Actions undertaken..." in the case where is_access_protected is true and all topic entries in Governance have enable_read_access_control and enable_write_access_control both true specifies that check_create_participant returns false. Thus the participant can't be created and this configuration won't be usable.

If the intent of enable_read/write_access_control is to defer to the Permissions document to determine both readability and write-ability of this participant (for the given topic) it would seem like this case should be supported and allowed by check_create_participant.

As part of resolving this issue we should also address DDSSEC12-85, meaning state whether a <default> clause should always be present.

Clarify interpretation of enable_read/write_access_control

Clarify behavior as suggested in issue description