Ultra-large-scale system (ULSS) is a computer science , software engineering, and systems engineering software. The scale of these systems gives rise to many problems: they will be developed and used by many stakeholders across multiple organizations, often with conflicting purposes and needs; they will be constructed from heterogeneous parts with complex dependencies and emergent properties; they will be continuously evolving; and software, hardware and human failures will be the norm, not the exception. The term ‘ultra-large-scale system’ was introduced by Northrop and others to describe challenges facing the United States Department of Defense . The term has subsequently been used to discuss challenges in many areas, including the computerization of financial markets.  The term ‘ultra-wide-scale system’ (ULSS) is sometimes used interchangeably with the term ‘large-scale complex IT system’ (LSCITS). These two terms were described in the US and the latter in the UK.
The term ultra-large-scale system was introduced in a report from the Software Engineering Institute at Carnegie Mellon University by Linda Northrop and colleagues.   The report explains that software intensive systems are reaching a set of stored values, accessed, manipulated, and refined; numbers of connections and interdependencies among components and numbers of hardware elements). When systems become ultra-large-scale, traditional approaches to engineering and management will no longer be adequate. The postponement Argues que le problem is no longer of engineering systems orsystem of systems , goal of engineering “socio-technical ecosystems”.
In 2013, Linda Northrop and her team conducted a review of the 2006 study and the reality of 2013. In summary, the discussion concludes that (a) ULS systems are in the midst of society and the changes of society. institutions are significant; (b) The 2006 original research team was probably too conservative in their report; (c) Recent technologies have exacerbated the pace of scale growth; and (d) There are great opportunities. 
At a similar time to the publication of the report by Northrop and others, a research and training initiative has been initiated in the UK on Large Scale Complex IT Systems . Many of the challenges recognized in this initiative have been identified as those of the ultra-large scale systems.  Greg Goth  quotes Dave Cliff , director of the UK initiative’re Saying “The ULSS proposal and the LSCITS proposal Were written Entirely indépendamment, yet we cam to very similar conclusions about what needs to be done and about how to do it “. A difference pointed out by Ian Sommerville  [ dead link ]is that the UK initiative began with a 5 to 10 year vision, while that of Northrop and her co-authors was much longer term. This is a different perspective on ultra-large-scale systems. For example, Richard Gabriel’s perspective is that of ultra-large-scale systems, which are desirable in the fields of software design and systems engineering.  On the other hand, Ian Sommerville’s perspective is that they are already emerging (for example in air traffic control), the key problem being that they are adequately engineered .  [ dead link ]
Characteristics of an ultra-large-scale system
Ultra-large-scale systems have the characteristics of systems of systems (systems that have: operationally independent sub-systems, managerially independent components and sub-systems, evolutionary development, emergent behavior, and geographic distribution). But in addition to these, the Northrop report  argues that a ULSS will:
- Have decentralized data, development, evolution and operational control
- Address inherently conflicting, unknowable, and various requirements
- Evolve with different capabilities being deployed
- Contain heterogeneous, inconsistent and changing elements
- Erode the people system boundary. People will not just be users, but the elements of the system and their overall emergent behavior.
- Encounter failure as the norm, rather than the exception, with it being extremely unlikely that all components are functioning at any one time
- Require new paradigms for acquisition and policy, and new methods for control
The Northrop report ULS systems will necessarily become decentralized in a variety of ways, developed and used by a wide variety of stakeholders with conflicting needs, and evolving continuously. The realities of software and hardware will be fundamentally integrated into the design and operation of ULS systems. require ULS systems will place demands on software acquisition, production, deployment, management, documentation, usage, and evolution practices. ”
Domains in which ultra-large-scale systems are emerging
The term ultra-large-scale system was introduced by Northrop and others  to discuss challenges faced by the United States Department of Defense in engineering software intensive systems. In 2008 Greg Goth wrote that although Northrop’s report focused on the US military’s future requirements, “its description of how the fundamental principles of software design will change in a global economy … is finding wide appeal”.  The term is now used to discuss problems in several domains.
The Northrop report argues that “the US Department of Defense (DoD) has a goal of information dominance … this goal depends on more complex systems of systems, sensors, decision nodes, weapons, and warfighters connected through heterogeneous wired and wireless networks These systems will be far larger than the size of today’s systems by … They will be ultra-large-scale systems. ” 
Following the flash crash , Cliff and Northrop  [ dead link ] -have argued “The very high degree of interconnectedness in the global markets means clustering That Entire trading systems, Implemented and managed separately by independent organisms, can rightfully be regarded as significant are entities in the larger global super-system… the sheer number of human agents and computer systems connected to the global financial-markets system-of-systems is so large that it is an instance of an ultra-large-scale system, and that largeness -of-scale has significant effects on the nature of the system “.  [ dead link ]
Kevin Sullivan has stated that the US healthcare system is “clearly an ultra-large-scale system”  and that building national scale cyber-infrastructure for healthcare “demands not just a rigorous, modern software and systems at the cutting edge of our understanding of information processing systems and their development and deployment in complex socio-technical environments “. 
Other domains, such as transmission systems, energy transmission systems (for example smart grids), and large enterprises.
Fundamental gaps in our current understanding of software and software development at the scale of ULS systems presents profound impediments to the technically and economically effective achievement of significant gains in core functionality. These gaps are strategic, not tactical. They are unlikely to be adequately addressed. Rather, we require a broad conception of both the nature of such systems and new ideas for how to develop them. We will need to look at them differently, not just as systems or systems of systems, but as socio-technical ecosystems. We will face fundamental challenges in the design and evolution, orchestration and control, and monitoring and assessment of ULS systems. These challenges require breakthrough research. 
ULSS research in the USA
The Northrop report  proposed a ULS systems research agenda for an interdisciplinary portfolio of research in at least the following areas:
Human interaction – People are key participants in ULS systems. Many problems in complex systems today stem from failures at the individual and organizational level. Understanding ULS system behavior will depend on the viewpoint of a person with a socially constituted computational process. This research involves anthropologists, sociologists, and social scientists conducting detailed socio-technical analyzes of user interactions in the field, with the goal of understanding how to construct and evolve such socio-technical systems effectively.
Computational emergence – ULS systems must satisfy the needs of participants at multiple levels of an organization. These participants will often behave opportunistically to meet their own objectives. Some aspects of ULS systems will be “programmed” by properly incentivizing and constraining behavior rather than by explicitly prescribing. This research area explores the use of methods and tools based on economics and game theory (eg, mechanism design) to ensure globally optimal ULS system behavior by exploiting the strategic self-interests of the system’s constituencies. This research area also includes exploring the evolution of cognitive limits of human development.
Design – Current Design Theory, Methods, Notations, Tools, and Practices. This research area broadens the traditional technology-centric definition of design to include people and organizations; social, cognitive, and economic considerations; and design structures such as design rules and government policies. It involves researching and designing ULS systems from all of these points of view and from many levels of abstraction, from the hardware to the software to the people and organizations in which they work.
Computational engineering – New approaches will be required to enable the control of systems and systems for design analysis, design, and operation.It will be defined in many languages, each with its own abstractions and semantic structures. This research area focuses on evolving the expressiveness of representations to accommodate this semantic diversity. ULS systems will evolve as a result of the complexity of ULS systems evolve.
Adaptive system infrastructure – ULS systems require an infrastructure that allows organizations to be distributed in parallel to develop, select, deploy, and evolve system components. This research area integrates integrated development environments and runtime platforms that support the decentralized nature of ULS systems. This research also focuses on technologies, methods, and theories that will enable ULS systems to be developed in their deployment environments.
Adaptable and predictable system quality – ULS systems will have to operate in a robust manner with failures, overloads, and attacks. These systems must be robust in the presence of adaptations that are not centrally controlled or authorized.
Traditional traditional traditional,,,,,,,,,,,,,,,,,, U U U U U U U U U U U U U U U. This research area focuses on maintaining the quality of a continuous system, continually failures, and attacks. It also includes identifying, predicting, and controlling new indicators of system health (akin to the US gross domestic product) that are needed because of the scale of ULS systems.
Policy, acquisition, and management – Policy and management frameworks for ULS systems, organizational, technical and operational policies at all levels. Rules and policies must be developed and automated to enable fast and effective local action while preserving global capabilities. This research area focuses on transforming acquisition strategies and processes to accommodate the rapid and continuous evolution of ULS systems by treating suppliers and supply chains as well as the essential components of a ULS system.
The proposed research does not supplant current, important software research aims rather significantly expands its horizons. Moreover, because it is focused on systems of the future, the SEI team purposely avoided couching descriptions in terms of today’s technology. The envisioned outcome of the proposed research is a spectrum of technologies and methods for developing these systems of the future, with national-security, economic, and societal benefits that extend far beyond ULS systems themselves.
ULSS research in the UK
The UK’s research program in Large-Scale Complex IT Systems  has been concerned with issues regarding ULSS development and considers that an LSCITS (Large-scale complex IT system) shares many of the features of a ULSS.
- System of systems
- Complex adaptive system
- Systems theory
- Systems design
- Software architecture
- Sociotechnical systems
- ^ Jump up to:a b c d e f g h Northrop, L., et al. “Ultra-Large-Scale Systems: The Software Challenge of the Future” , Carnegie Mellon Software Engineering Institute, Ultra-Large-Scale Systems Study Report (2006)
- ^ Jump up to:a b c Cliff, D., and Northrop, L. “The Global Financial Markets: An Ultra-Large Scale Systems Perspective” , briefing paper for UK Government Office for Science Foresight project on The Future of Computer Trading in the Financial Markets (September 2011) Archived December 26, 2011 at the Wayback Machine .
- Jump up^ Ultra Wide Scale Systems Website
- Jump up^ Northrop, Linda. “Does Scale Really Matter? Ultra-Large-Scale Seven Years Systems After The Study” (PDF) . Software Engineering Institute, Carnegie Mellon University . Retrieved 19 May 2014 .
- ^ Jump up to:a b c Sommerville I Ultra Large Scale Systems Read Slides on Systems Engineering for LSCITS
- ^ Jump up to:a b Goth G. “ultra Systems: Refining Software Engineering?” IEEE Software, March / April 2008 [ dead link ]
- Jump up^ Gabriel, RP,Beyond Human Abilities Design, Transcript of Wei Lun Reading at the Chinese University of Hong Kong, 16 November 2007Archived23 April 2009 at theWayback Machine.
- ^ Jump up to:a b Sullivan, K. Cyber-Social Systems Approach to the Engineering of Ultra-Large-Scale National Health Information Systems. National Institute of Medicine, 19 August 2011
- Jump up^  Archived3 November 2011 at theWayback Machine.