Complex systems are defined as systems with many interdependent parts which give rise to non-linear and emergent properties determining the high-level functioning and behavior of such systems. Due to the interdependence of their constituent elements and other characteristics of complex systems, it is difficult to predict system behavior based on the ‘sum of their parts’ alone. Examples of complex systems include bee hives, bees themselves, human economies and societies, nervous systems, molecular interactions, cells and living things, ecosystems, as well as modern energy or telecommunication infrastructures. Arguably one of the most striking properties of complex systems is that conventional experimental and engineering approaches are inadequate to capture and predict the behavior of such systems.

To complement the conventional experimental and engineering approaches, computer-based simulations of complex natural phenomena and complex man-made artifacts are increasingly employed across a wide range of sectors. Typically, such simulations require computing environments which meet very high specifications in terms of processing units, primary and secondary storage, and communication. Supercomputers constitute the de facto technology to deliver the required specifications. Acquiring, operating and maintaining supercomputers involve considerable costs, which many organizations cannot afford. The working assumption of the QosCosGrid project is that a grid could be enhanced by suitable middleware to provide features and performance characteristics that resemble those of a supercomputer. We refer to such a grid as quasi-opportunistic supercomputer. The QosCosGrid projects aim is to develop such a system.