 In this video, we'll be giving an outline to what we mean by the term complex engineered system. Like all systems, technologies can be simple linear systems or complex non-linear systems. To understand the difference, we'll firstly discuss the classical characteristics of simple linear systems before moving on to itemize the defining features to complex engineered systems with some examples. In the previous module, we've talked about and defined technology as automated systems for solving some given environmental constraint. As such, they are physical systems that automatically act out an algorithm for solving a problem. A screwdriver is a system that automates part of the process that is required to overcome the physical constraints needed to put a screw into a material. A bridge is an automatic system for solving the problem of getting from one side of a river to another. These are examples of simple linear systems. To illustrate some of the characteristics to linear technologies, we'll take a common household toaster as an example. Firstly, linear systems are composed of a finite amount of interacting components. Our toaster may have a maximum of a few hundred components. Thus, it is possible to itemize and describe each component in the system. Because of this, it is often possible to define a fixed boundary for these simple systems. They are what we call well-bounded. By this, I mean that we can tell exactly what is part of the system and what is not. We can put our toaster in a box and say that what is in the box is part of the toaster and what is outside the box is not part of the toaster. This may sound like a trivial observation, but it is certainly not always the case that we can actually do this. And it is typically only with these simple linear systems that we can really define a fixed meaningful boundary. Linear systems have a relatively low level of connectivity between the components and with other systems in their environment. Added to this, components interact in a well-defined linear fashion. There is a limited amount of interactions in our toaster, and it is often possible for us to draw direct cause and effect interactions between any two components that are connected. Also, we can define and quantify exactly the operational inputs and outputs to the toaster. A single source of electricity and bread goes in, with toast coming out. And there is a single simple parameter to the system's operation. One dial for varying how well we want our toast cooked. Next, linear systems are homogeneous, meaning the system performs one single function and all components are designed towards that same function. Our toaster makes toast. You can't use it to cook omelettes or make telephone calls with it. A corollary to this is that these systems are monolithic, meaning that all subsystems and components are all constrained by one top-down design pattern. Individual components have a well-defined function that is constrained within strict operating parameters governed by the system's overall design. One engineering team designed our toaster. They designed the whole system, choosing each component in order to optimize the functioning of the whole system. Because of this, these simple engineered systems are well-defined engineered objects and they are expected to be well-behaved in their functioning, meaning they operate in a standardized, routine and predictable fashion. Complex engineered systems are qualitatively different from these linear technologies. To help illustrate this, we'll take the classical example of a city. Firstly, complex engineered systems are open systems, meaning that they have such a high level of interaction with their environment that their boundary is not well-defined. Added to this, they are composed of a very many elements. We may be talking about millions, billions, or even too many components for us to be able to quantify in any meaningful way. And it may be very difficult to say which of these components are part of the system and which are not. For example, metropolitan areas may span large geographical areas as different urban centers morph into each other. We might draw lines on a map in order to define jurisdiction, but from an engineering perspective, these are largely arbitrary. Asking how many components there are in the system is again a somewhat arbitrary question. For all intensive purposes, it is essentially infinite. We cannot itemize each component in the system. Added to this, components are leaving and joining, coupling and decoupling from the system in a dynamic fashion. Metropolitan areas provide critical services that a whole region or country's infrastructure is dependent upon. They are deeply interconnected and interdependent on their environment. At this critical level of connectivity and interdependence, the system becomes more open than closed and it is defined less by its boundary and more by the flow of resources through the system. As opposed to simple systems where components interact in a linear fashion. In complex systems, components interact in a non-linear pattern. Processes don't just take place from start to finish independently along one sequential process. Instead, many different processes and functions are taking place within a parallel architecture. They interact across and between processes and domains in a networked fashion. A metro area is a composite of many overlapping parallel infrastructure systems from transportation and water supply to electrical power grid and the telecommunications networks. The components in the system are not just interacting across domains but also across scales. Complex engineered systems are what are called systems of systems. They have a multi-layered hierarchical structure as elements form part of subsystems which form part of larger systems which in turn form part of the whole system of systems. A subway train is part of the mass transit system which is part of the transportation system which in turn combines with many other systems to form the whole urban environment. What is important when we're looking at the whole system is how these different subsystems interrelate. That is, do they interact in a constructive or destructive fashion. For example, is the airport in our metropolis built right beside a major residential area resulting in noise pollution. A destructive relation that reduces the functionality of the whole system. Processes that were designed in isolation to function in a linear fashion lack integration with other systems in their environment. We get a dead-end effect and the production of waste that will be destructive to some other subsystem. For example, when we build large tarmac surfaces that can't absorb rainwater the result is a high level of runoff that needs to be dealt with by the wastewater system. This is often the case when we use a reductionist design paradigm it results in a focus on the individual components without full regard for how these components interrelate to give us the functionality of the whole system. Thus we often end up with optimal solutions on the micro level but sub-optimal solutions on the macro scale. When components interact in a constructive fashion we get synergies. They complement and enable each other. We can think about the use of greenways and parks to absorb carbon emissions in a city. The coordination between consumers and producers of electricity on a smart grid or the schedule coordination between different modes of transportation. These are examples of synergies. Through synergies we get the emergence of new levels of organization and global functionality. Ultimately, all of this technology and infrastructure that constitutes our metro area is about delivering a material quality of life to the citizens. Most of these infrastructure systems users don't own. They just have access to the service. Material quality of life is not a single product or thing. It is about everything working together so that we get the emergence of a seamless set of services enabling end users to live a high material quality of life. And these different types of relations and interactions are a defining factor in whether the infrastructure system can deliver this emergent macro scale functionality that everybody wants. Synergies within complex engineered systems require both intelligent design and the use of information technology to coordinate different systems in real time. Next, we'll talk about networks. Unlike our toaster that was a homogeneous system these complex engineered systems are not. As mentioned, they're really composite entities made up of many different elements and subsystems heterogeneous components that were never really designed to work together. The system is distributed out. No one is really in control and the whole thing is really just a network of connections. Our metro area is the product of thousands or even millions of different actors. Businesses deciding what projects to invest in public administrators deciding which projects to support citizens choosing where to live and where to send their children to school. All of these different actors and subsystems are only loosely associated with each other. Think about the internet of things where many billions of devices from smartphones to tractors to hospitals couple and decouple from the system dynamically and operate under their own internal logic. These complex engineered systems are really networks that link up many heterogeneous subsystems and components and this helps to emphasize the important fact about autonomy that is the components are largely autonomous they're not fully constrained by the system. This runs very much contrary to our traditional idea of engineering where control over the entire system is thought to be a prerequisite with systems designed in a top-down fashion. But this is not how the internet was created nor electrical power grids nor our metro area they all started small and evolved to become the complex systems they are today. Evolution is a process of development that acts on all technologies on all scales. The electrical power grid is a good example since its inception in the industrial age electrical grids have evolved from local systems that served a particular geographical area to wider expansive networks that incorporate multiple areas typically covering whole nations. At no point was there the option to simply build the whole national electrical infrastructure from scratch as a homogeneous system. The US power transmission grid for example, consists of about 300,000 km of line operated by approximately 500 companies and through distributed generation it is rapidly evolving into a next generation smart grid that will expand the number of producers drastically making for many, many actors acting and reacting to each other's behaviour as the entire system evolves over time. It is an example of what is called a complex adaptive system. So this is an outline to what we mean when we use the term complex engineered system. There are large technologies composed of many diverse subsystems that are densely interacting in a non-linear fashion to create a multi-tiered network system that evolves over time. To give some other examples we could cite airports, logistics networks, telecommunications networks, enterprise information systems, IoT platforms and the internet itself, hospitals and healthcare systems, the global air transportation network and all types of infrastructure systems from mass transit to water supplies.