When implementing an application system in a distributed computing environment, several architectural questions arise such as, how and where computing resources are distributed, and how the communication among computing resources should be implemented. To simplify the process of making these choices, we have developed a distributed computing model. This model classifies distributed processing systems into seven categories based on the location of data storage and the style of processing between client and server. This paper describes our model and its use in planning the infrastructure of a new system for one of our customers.