One version of Polk's implementation of Clark-Wilson on UNIX systems requires transaction procedures to distinguish users in order to determine which CDIs the user may manipulate. This exercise asks you to explore the implementation issues in some detail.

a. Polk suggests using multiple copies of a single TP. Show, with examples, exactly how to set this up.

b. Polk suggests that wrappers (programs that perform checks and then invoke the appropriate TPs) could be used. Discuss, with examples, exactly how to set this up. In particular, what checks would the wrapper need to perform?

c. An alternative implementation would be to combine the TPs and wrappers into a single program. This new program would be a version of the TP that would perform the checks and then transform the CDIs. How dificult would such a combination be to implement? What would be its advantages and disadvantages compared with multiple copies of a single TP? Compared with the use of wrappers?