Methods, systems and computer programs for verifying permissioning rights to one or more data resources associated with a data processing platform (DPP) are disclosed. An exemplary method comprises receiving an assertion statement identifying a user, a data resource and an operation performable with respect to the data resource; in response to receiving the assertion statement, generating a hierarchical representation of an access control list for the data resource identified in the statement and evaluating the hierarchical representation against a current state of permissions to determine if the received assertion statement is true or false in relation to said data resource identified in the assertion statement; in response to determining that the assertion is false, generating an error message for output.