Validity was donated by GammaStream Technologies.
From their site: Validity is a framework (Validity) and a WebObjects application (Validity Modeler) which combine to provide a powerful data validation engine and validation rule modeler. Using an EOModel as a reference point, one may assign rules to the various attributes of the entities. One may choose from any of Validity's predefined rules, or write his/her own rules in Java. The rules are stored in the Validity model file (Validity.model) inside the corresponding '.eomodeld' wrapper.
Validity has two parts: a framework and a tool (ValidityModeler).
Use tool to add validation rules to your .eomodeld.
The framework hooks into your EOs' validateFor[Insert|WO:Save|Update|Delete] methods.
Framework engine applies rules at runtime and throws an exception if a rule is broken.
Using Validity results in less validation code in your own enterprise objects.