WHAT IS CLAIMED IS: 1. A method of providing Resource-Event-Agent (REA) model based security, the method comprising: identifying an association between a first object and a second object in an REA model; creating an association class for the association between the first object and the second object, the association class defining security between the first object and the second object. 2. The method of claim 1, wherein creating the association class for the association between the first object and the second object further comprises creating an association class object having properties, the properties of the association class object defining the security between the first object and the second object. 3. The method of claim 2, wherein creating the association class object further comprises creating one or more association class objects having properties, the properties of the one or more association class objects defining security between a first class of objects of which the first object is a member and a second class of objects of which the second object is a member. 4. The method of claim 2, wherein the second object is a securable object. 5. The method of claim 4, wherein the first object is of a particular agent type, and wherein a role for a user is defined by the particular agent type for the first object. 6. The method of claim 5, wherein the second object is a contract or agreement type object. 7. The method of claim 5, wherein the second object is a commitment type object. 8. The method of claim 5, wherein the second object is an event type object. 9. The method of claim 5, wherein the second object is a resource type object. 10. The method of claim 5, wherein the second object is an agent type object. 11. The method of claim 5, wherein identifying the association between the first object and the second object further comprises identifying a control type association between the first object and the second object. 12. The method of claim 5, wherein identifying the association between the first object and the second object further comprises identifying a custody type association between the first object and the second object . 13. The method of claim 5, wherein creating the association class for the association between the first object and the second object further comprises creating the association class in a security model. 14. The method of claim 13, wherein creating the association class in the security model further comprises creating the association class in the security model separate from the REA model. 15. The method of claim 13, wherein creating the association class in the security model further comprises creating the association class in the security model as part of the REA model. 16. The method of claim 13, wherein defining security between the first object and the second object further comprises defining permissions and rights of the first object relative to the second object. 17. The method of claim 16, wherein defining permissions and rights of the first object relative to the second object further comprises dynamically determining the permissions and rights in a security policy logic module outside of the security model. 18. A computer readable medium having computer- executable instructions for performing steps of the method of any of claims 1-17. 19. A system configured to implement the method of any of claims 1-17. 20. A system for providing security, the system comprising: a Resource-Event-Agent (REA) model configured to implement a first object, a second object, and an association between the first object and the second object; a security model configured to implement an association class for the association between the first object and the second object in the REA model, such that the association class defines security between the first object and the second object. 21. The system of claim 20, wherein the association class for the association between the first object and the second object further comprises an association class object having properties, the properties of the association class object defining the security between the first object and the second object. 22. The system of claim 21, wherein the association class object further comprises one or more association class objects having properties, the properties of the one or more association class objects defining security between a first class of objects of which the first object is a member and a second class of objects of which the second object is a member. 23. The system of claim 21, wherein the security model is separate from the REA model. 24. The system of claim 21, wherein the security model is part of the REA model. 25. The system of claim 21, and further comprising a security policy logic module coupled to the security model and configured to dynamically determine permissions and rights of the first object relative to the second object.