This paper surveys some of the issues involved in building useful distributed systems involving PC's and hosts. Alternative communications techniques for micro-mainframe communication are compared. The point of view is presented that the PC user should be provided with a unified view of the heterogeneous distributed system to which he is connected. The proposed method is to formalize the notion of a service request and provide distributed services by function shipping service requests to remote nodes able to provide the service, e.g., personal computers will ship requests which they cannot satisfy locally to hosts on the network. Providing a unified view of data which allows PC application programs to access files on mainframes is an example of a service which can be built by intercepting and shipping service requests. Examples from current IBM products are used to illustrate approaches. The views presented are the authors' own, based on systems research in progress at the IBM Thomas J. Watson Research Center.

A new model of the software development process is presented and used to derive the form of the resource consumption curve of a project over its life cycle. The function obtained differs in detail from the Rayleigh curve previously used in fitting actual project data. The main advantage of the new model is that it relates the rate of progress which can be achieved in developing software to the structure of the system being developed. This leads to a more testable theory, and it also becomes possible to predict how the use of structured programming methods may alter pattems of life cycle resource consumption.