Design of complex systems: issues and challenges

Several techniques currently exist to design complex systems. The most common technique used is to divide complex systems into smaller modules (or subsystems), build the modules separately, and later integrate them. Depending on the user requirements and domain-specific and system-specific characteristics, the division is based on factors such as functionality, geographical locations (within the system), and inter-component interactions. Resulting modules have well-defined interfaces. An interface is an abstraction through which the internal details of a module are hidden from other modules. Understanding and tracking the relationships between modules is very important. This paper presents various factors that have to be considered during division of systems. Reuse is the most popular method used to build the modules. Reuse is the process of building systems from existing systems rather than building them from scratch. This concept utilizes general methods and experience of the domain life cycle from earlier product developments, which results in improved productivity, quality and efficiency, while minimizing man-hours, cost, and complexity. Abstraction, selection, customization, and integration are the four steps of this approach (Krueger, 1992). Among these, integration is the most complicated step. Fewer the modules to integrate, easier the integration, but smaller is the chance of reusability. On the other hand, smaller modules result in efficient reuse, but complex integration process. Thus, there is a tradeoff between reusability and integration. Using examples from various domains such as software engineering and health management systems, this paper discusses the concepts mentioned.