1. A computer-implemented method executed by one or more computing devices for specifying a legality expression for use in a system for processing said legality expression, said method comprising: selecting, by at least one of the one or more computing devices, at least one digital data element from a legality expression language, including at least one of, a duty element specifying an obligation that a principal must perform an act, a ban element specifying a prohibition that a principal must not perform an act, and a claim element specifying an assertion that a principal does perform an act; determining, by at least one of the one or more computing devices, at least one attribute value for the at least one data element; transforming, by at least one of the one or more computing devices, the at least one digital data element and the at least one attribute to create a legality expression; and recording, by at least one of the one or more computing devices, the legality expression in a form that can be interpreted by the system for processing legality expressions to thereby permit the system to enforce the legality expression.