As enterprises begin to increasingly conduct their businesses over multiple interconnected networks spanning many countries using large computer systems, there is a need to be able, to specify, represent and manipulate enterprise policies in these systems so as to be able to efficiently monitor and regulate enterprise processes and business transactions. A large enterprise typically comprises of hundreds of smaller units that to a large extent operate independently but within the overall goals of the enterprise. To reduce any bottlenecks or delays in everyday operations of enterprise units, it should be possible for various enterprise unit heads to create, delete or modify policies relevant to them with minimum reliance on a centralized policy administrator. However, when multiple users begin to manage enterprise policies, there is a need to identify "who can create policies on what resources" and "who should follow these policies". Also, when multiple units compete for common resources, policy conflicts may arise. It is important to detect and resolve conflicts between policies before accepting them for enforcement.  An Enterprise Policy Specification Tool (PST) is introduced in this thesis that provides a solution to the above problems. The tool is unique since it provides a model-driven policy specification language that incorporates constructs to denote the enterprise model in the specified policies. We have defined policy conflicts that can arise and provide a mechanism to detect and resolve them at the time of specification. Although our proposed model is domain independent, the implementation and testing have been carried out in the context of a Message Notification System. A Java-based partial implementation of our proposed architecture has demonstrated the feasibility of the model-based approach to policy specification