Application of the Four Variable Model to a CAD System for Microwave Communications Devices

Mr. Yun Zou


This report studies the application of the four-variable requirements model to a CAD system for microwave communications systems (CADMCS), a complex non-real-time software package. The documentation of the complete system requirements for the CADMCS system is presented.

The four variable model is reviewed in detail. Based on the characteristics of CAD systems, the techniques to control the complexity using the well-known principles such as information-hiding, separation of concerns or divide-and-conquer are discussed. The use of well-known mathematical concepts such as vectors, vector functions, as well as geometry objects as the types of the monitored and controlled variables is demonstrated. A new classification of the monitored and controlled variables is also introduced to make the documentation easier to understand and serve as the mechanism to support a hierarchical system structure.

This work demonstrates the recursive decomposition of the monitored and controlled variables. Relational algebra has been applied to presenting and organizing the REQ (requirements) relation in the CADMCS system. The report shows how complex relations can be described in terms of simpler sub-relations using the decomposition operator of relational algebra.