RuleGen is a framework written in PL/SQL that generates code to maintain data integrity constraints. Right now RuleGen implements table constraints, i.e. at most one president allowed in EMP, and database constraints, i.e. every department has at least two employees. Enforcing a data integrity constraint is done in two steps. The first step is about administering the affected rows of a transaction (inserts, updates and deletes). The second step is validating the constraint against the affected rows. If the constraint is violated an exception is raised. You can also say the first step is about WHEN the constraint is validated and the second step is HOW the constraint is validated.
There are switches to influence the runtime behavior of RuleGen like the execution model: stop on the first constraint violation or continue after the first constraint violation in order to collect a list of constraint violations (like the message stack in CDM Ruleframe). It is also possible to defer checking (in contrary to immediate checking).
A difference between CDM Ruleframe and RuleGen is the relationship with Oracle Designer. RuleGen is not integrated with Oracle Designer where CDM Ruleframe is. The definition (remember HOW and WHEN) of data integrity constraints is either done with SQL*Plus or with a small APEX application. Another difference between RuleGen and CDM Ruleframe is there is no PL/SQL coding required with RuleGen. The definition of data integrity constraints is done in SQL queries completely.
In my opinion, the functionality of RuleGen looks very promising. Keep an eye on it!