International Symposium on Software Composition

Ultra-large-scale systems

Ultra-large-scale system (ULSS) is a term used in fields including Computer Science, Software Engineering and Systems Engineering to refer to software intensive systems with unprecedented amounts of hardware, lines of source code, numbers of users, and volumes of data. 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-large-scale system' (ULSS) is sometimes used interchangeably with the term 'large-scale complex IT system' (LSCITS). These two terms were introduced at similar times to describe similar problems, the former being coined in the USA and the latter in the UK.

In 2013, Linda Northrop and her team conducted a talk to review outcome of the 2006 study and the reality of 2013. In summary, the talk concluded that (a) ULS systems are in the midst of society and the changes to current social fabric and 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 was being initiated in the UK on Large-scale Complex IT Systems. Many of the challenges recognized in this initiative were the same as, or were similar to those recognized as the challenges of ultra-large-scale systems. Greg Goth quotes Dave Cliff, director of the UK initiative as saying "The ULSS proposal and the LSCITS proposal were written entirely independently, yet we came to very similar conclusions about what needs to be done and about how to do it". A difference pointed out by Ian Sommerville 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 seems to have led to there being two slightly different perspectives on ultra-large-scale systems. For example, Richard Gabriel's perspective is that ultra-large-scale systems are desirable but currently impossible to build due to limitations in the fields of software design and systems engineering. On the other hand, Ian Sommerville's perspective is that ultra-large-scale systems are already emerging (for example in air traffic control), the key problem being not how to achieve them but how to ensure they are adequately engineered.

The Northrop report states that "the sheer scale of ULS systems will change everything. ULS systems will necessarily be decentralized in a variety of ways, developed and used by a wide variety of stakeholders with conflicting needs, evolving continuously, and constructed from heterogeneous parts. People will not just be users of a ULS system; they will be elements of the system. The realities of software and hardware failures will be fundamentally integrated into the design and operation of ULS systems. The acquisition of a ULS system will be simultaneous with its operation and will require new methods for control. In ULS systems, these characteristics will dominate. Consequently, ULS systems will place unprecedented demands on software acquisition, production, deployment, management, documentation, usage, and evolution practices."

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 argued that "the U.S. Department of Defense (DoD) has a goal of information dominance Ĺ this goal depends on increasingly complex systems characterized by thousands of platforms, sensors, decision nodes, weapons, and warfighters connected through heterogeneous wired and wireless networks. Ĺ These systems will push far beyond the size of today's systems by every measure Ĺ They will be ultra-large-scale systems.

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 engineering effort, but an approach at the cutting edge of our understanding of information processing systems and their development and deployment in complex socio-technical environments".

Fundamental gaps in our current understanding of software and software development at the scale of ULS systems present profound impediments to the technically and economically effective achievement of significant gains in core system functionality. These gaps are strategic, not tactical. They are unlikely to be addressed adequately by incremental research within established categories. Rather, we require a broad new 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.

Policy, acquisition, and management – Policy and management frameworks for ULS systems must address 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 policies and processes to accommodate the rapid and continuous evolution of ULS systems by treating suppliers and supply chains as intrinsic and essential components of a ULS system.

The proposed research does not supplant current, important software research but 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.