13. A method, operative within a federated environment in which a token service fulfills requests by executing a module chain comprising a set of modules, comprising: defining a custom module to include one or more name-value pairs, wherein a given name-value pair has a value that may be validated against a rule; responsive to receipt of a token, initiating processing of the module chain that includes the custom module within a computing entity; during processing of the custom module within the computing entity, attempting to validate the value of a name-value pair based on the rule, wherein the rule is determined during the processing of the custom module based on one or more invocation parameters of the module chain; and returning a response.
13. A method, operative within a federated environment in which a token service fulfills requests by executing a module chain comprising a set of modules, comprising: defining a custom module to include one or more name-value pairs, wherein a given name-value pair has a value that may be validated against a rule; responsive to receipt of a token, initiating processing of the module chain that includes the custom module within a computing entity; during processing of the custom module within the computing entity, attempting to validate the value of a name-value pair based on the rule, wherein the rule is determined during the processing of the custom module based on one or more invocation parameters of the module chain; and returning a response. 15. The method as described in claim 13 wherein the token is received upon a user of a first entity attempting a federated single sign-on (F-SSO) to the federated environment.