Systems are sets of entities, physical or abstract, comprising a whole where each component interacts with or is related to at least one other component and they all serve a common objective. The scientific research field which is engaged in the interdisciplinary study of universal system-based properties of the world is general system theory, systems science and recently systemics. This field investigates the abstract properties of matter and mind, and their organization, searching for concepts and principles which are independent of the specific domain, substance, and type of system, and of the spatial and/or temporal scales of its existence.
Systems science can be viewed as ... "a metalanguage of concepts and models for interdisciplinary use, still now evolving and far from being stabilized. This is the result of a slow process of accretion through inclusion and interconnection of many notions, which came and are still coming from very different disciplines. The process started more than a century ago, but has gathered momentum since 1948 through the pioneering work of Norbert Wiener, John von Neumann, Ludwig von Bertalanffy, Heinz von Foerster and W. Ross Ashby, among many others" (Charles François, 1999).
An immune system is a collection of mechanisms within an organism that protects against infection by identifying and killing pathogens and tumor cells. It detects a wide variety of pathogens, such as viruses and parasitic worms and distinguishes them from the organism's normal cells and tissues. Detection is complicated as pathogens adapt and evolve new ways to successfully infect the host organism.
Systems engineering techniques are used in complex projects: from spacecrafts to chip design, from robotics to creating large software products to building bridges, Systems engineering uses a host of tools that include modeling & simulation, requirements analysis, and scheduling to manage complexity.