A system is an aggregation of subsystems cooperating so that the system is able to deliver the overarching functionality. System integration involves integrating existing often disparate systems. System integration is also about adding value to the system, capabilities that are possible because of interactions between subsystems.
In today’s connected world, the role of system integration engineers is becoming more and more important: more and more systems are designed to connect, both within the system under construction and to systems that are already deployed. A system integration engineer needs a broad range of skills and is likely to be defined by a breadth of knowledge rather than a depth of knowledge. System integrators are likely to encounter new and challenging problems with an input from a broad range of engineers where they pull it all together into a functioning system.