25. The data processing system as described in claim 23 wherein the operations further include: generating an internal representation of information in the token; and evaluating the internal representation to determine if all name-value pairs expected to be in the token are contained within the token; wherein the evaluating step is performed on a name of each name-value pair.
23. A data processing system for use in a federated environment in which a token service fulfills requests by executing a module chain comprising a set of modules, comprising: a processor; computer memory holding computer program instructions that, when executed by the processor, perform the following operations: 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; during processing of the custom module, 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.