The area of mathematics/computer security that the problem will be from is an area known as Non-Interference. For the development of highly secure systems, it is crucial that all information flows through the system are understood. In particular, covert channels or unexpected information flows can be particularily damaging to a secure system which is attempting to maintain a high level of confidentiality. (For example, a top secret process should not under normal situations be able to send or otherwise signal any information to a secret process.) Non-Interference is a mathematical technique that allows a system model to be analyzed for these kinds of information. Traditionally these non-interference techniques or theorems have been stated in a hierarchical (POSet based) fashion. That is, they have emphasized a military approach where information is labelled "top secret" or "secret" and no information from "top secret" is allowed to flow to "secret". Recently there have been attempts to generalize this approach, to allow information to flow between processes in a non-hierarchical (non partially ordered set) way. The problem will be to examine this new framework, and to work some small examples to gain an understanding of this approach and to validate whether or not in can be used to actually analyze real systems.