Clark Wilson Integrity Model: Rules

Question

What is the conceptual difference between certification rules and enforcement rules in the Clark Wilson model?

Am I on a wrong path when I assume that certification rules ensure external integrity and enforcement rules ensure internal integrity?

Answer 1

I would say that the conceptual difference is one of primary functionality.

Certification Rules lay out how the system certifies that a particular data object is in a valid state (according to another set of rules). Enforcement Rules make sure that already-certified data object stays certified (maintains its integrity) as the system interacts with it.

To be more specific using Clark Wilson IM vernacular:

Certification rules specify how to guarantee that a CDI has been subjected to integrity verification procedures. Enforcement rules specify how the system must maintain the certified CDI as transactions happen.