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Ultra Large Scale Systems

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Ultra Large Scale Systems, York EngD programme, 2010 Slide 1
Ultra Large Scale Systems
Ian Sommerville

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Ultra Large Scale Systems, York EngD programme, 2010 Slide 2
Objectives
• To discuss the notion of ULSS systems
• To intro...

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Ultra Large Scale Systems, York EngD programme, 2010 Slide 3
Acknowledgements
• Much of the material in this presentation ...

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Ultra Large Scale Systems

  1. 1. Ultra Large Scale Systems, York EngD programme, 2010 Slide 1 Ultra Large Scale Systems Ian Sommerville
  2. 2. Ultra Large Scale Systems, York EngD programme, 2010 Slide 2 Objectives • To discuss the notion of ULSS systems • To introduce the SEI study report on ULSS
  3. 3. Ultra Large Scale Systems, York EngD programme, 2010 Slide 3 Acknowledgements • Much of the material in this presentation has been derived from: • Ultra-large Scale Systems – Linda Northrop, Software Engineering Institute, Pittsburgh – Presented at the St Andrews Workshop on Socio-technical Systems, September 2009.
  4. 4. Ultra Large Scale Systems, York EngD programme, 2010 Slide 4 From LSCITS to ULSS • At around the same time as the LSCITS research and training initiative was being considered in the UK, a related study was underway looking at issues around ultra large scale systems • LSCITS: 5-10 year perspective • ULSS: 10-20 year perspective • ULSS study was about identifying research requirements rather than doing research. • Completely independent initiatives but considerable overlap in conclusions
  5. 5. Ultra Large Scale Systems, York EngD programme, 2010 Slide 5 ULSS Report • ULSS report, published in 2006 • Report of a study commissioned by US DoD on the future of software • Identifies what is meant by an ULSS • Identifies research areas and challenges
  6. 6. Ultra Large Scale Systems, York EngD programme, 2010 Slide 6 Societal problems • Society is facing major problems and challenges – Climate change – Ageing populations in developed countries – Feeding a growing world population – Power for a developing world – Safety and security – Managing megacities • Without doubt, these problems can only be addressed using large and complex software systems • However, these are ‘wicked problems’ – we cannot specify them in detail so an evolutionary approach to systems engineering is essential
  7. 7. Ultra Large Scale Systems, York EngD programme, 2010 Slide 7 Ultra large scale systems • A ULS System has unprecedented scale in some of these dimensions: • lines of code • amount of data stored, accessed, manipulated, and refined • number of connections and interdependencies • number of hardware elements • number of computational elements • number of system purposes and user perception of these purposes • number of routine processes, interactions, and “emergent behaviors” • number of (overlapping) policy domains and enforceable mechanisms • number of people involved in some way
  8. 8. Ultra Large Scale Systems, York EngD programme, 2010 Slide 8 ULSS • ULS systems will be interdependent webs of software- intensive systems, people, policies, cultures, and economics. • ULS systems are systems of systems at internet scale • The boundary between a ULSS and an LSCITS is a very blurred one. In some cases, it may be appropriate to think of these terms as synonymous but the general implication in the report is that ULSS have all of the characteristics of an LSCITS but at an even larger scale – The purpose of an ULSS is typically broader than that of an LSCITS and a ULSS will normally include many LSCITS
  9. 9. Ultra Large Scale Systems, York EngD programme, 2010 Slide 9 Do ULSS exist? • My reading of the report is that it envisages a ULSS as a web of interconnected automated systems. The ULSS report assumes that these systems do not yet exist. • However, what about: – The World Wide Web – International air traffic control – Portfolio of applications in a major multinational company across several continents
  10. 10. Ultra Large Scale Systems, York EngD programme, 2010 Slide 10 ULSS and SoS • Purpose vs Opportunism – SoS are integrated and built to fulfil specific purposes – ULSS have no single well-defined purpose (although they may be created to support from broad goal such as safe air traffic management or intercontinental power management). From ULSS, more specific systems are created to tackle individual problems • Centralisation vs Decentralisation – SoS have a single centralised authority and an agreed purpose e.g. the Navy are the authority for SoS on a warship – ULSS have no centralised authority and no agreement amongst stakeholders on the purpose of the system
  11. 11. Ultra Large Scale Systems, York EngD programme, 2010 Slide 11 Scale changes everything • Characteristics of ULS systems arise because of their scale. – Decentralization – Inherently conflicting, unknowable, and diverse requirements – Continuous evolution and deployment – Heterogeneous, inconsistent, and changing elements – Erosion of the people/system boundary – Normal failures – New paradigms for acquisition and policy • These characteristics may appear in today’s systems and systems of systems, but in ULS systems they dominate. • These characteristics undermine the assumptions that underlie today’ssoftware engineering approaches.
  12. 12. Ultra Large Scale Systems, York EngD programme, 2010 Slide 12 Today’s approaches • The Engineering Perspective - for large scale software-intensive systems • largely top-down and plan-driven • requirements/design/build cycle with standard well-defined processes • centrally controlled implementation and deployment • inherent validation and verification • The Agile Perspective - proven for smaller software projects • fast cycle/frequent delivery/test driven • simple designs embracing future change and refactoring • small teams and retrospective to enable team learning • tacit knowledge • Today’s approaches are based on perspectives that fundamentally do not cope with the new characteristics arising from ultra-large scale. • The mentality of looking backward doesn’t scale.
  13. 13. Ultra Large Scale Systems, York EngD programme, 2010 Slide 13 Systems as buildings
  14. 14. Ultra Large Scale Systems, York EngD programme, 2010 Slide 14 ULSS as cities
  15. 15. Ultra Large Scale Systems, York EngD programme, 2010 Slide 15 Are ULSS like cities? • Cities (in developed countries) are controlled entities – There is an elected local city government that is responsible for coordinating work on utilities, managing disruption to citizens, approving plans for development, etc. – Cities only work successfully because of this local government – they have not just evolved. – Without this central control, cities were dangerous places with high crime levels, dangerous buildings, uncontrolled development, high levels of disease and poverty, etc. • Who will play the role of the ‘city council’ for ULSS? • Will the lack of such a role hinder the development of ULSS?
  16. 16. Ultra Large Scale Systems, York EngD programme, 2010 Slide 16 Socio-technical ecosystems • Socio-technical ecosystems include – People, organizations, and technologies at all levels with significant and often competing interdependencies. – There will be competition for resources. – There will be organizations and participants responsible for setting policies. – There will be organizations and participants responsible for producing ULS systems. – There will need to be local and global indicators of health that will trigger necessary changes in policies and in element and system behavior.
  17. 17. Ultra Large Scale Systems, York EngD programme, 2010 Slide 17 Central challenges of ULSS • Design and evolution • Orchestration • Monitoring and assessment • Organizational integration • Regulation and control
  18. 18. Ultra Large Scale Systems, York EngD programme, 2010 Slide 18 Design and Evolution • Specific challenges in ULS system design and evolution stemming directly from the characteristics of ULS systems: – Economics and industry structure – Social activity for constructing computational environments – Legal issues – Enforcement mechanisms and processes – Definition of common services supporting the ULS system – Rules and regulations – Agility – Handling of change – Integration – User-controlled evolution – Computer-supported evolution – Adaptable structure – Emergent quality
  19. 19. Ultra Large Scale Systems, York EngD programme, 2010 Slide 19 Orchestration and control • Orchestration and control refers to the set of activities needed to make the elements of a ULS system work together in reasonable harmony to ensure continuous satisfaction of mission objectives. • Orchestration is needed at all levels of ULS systems and challenges us to create new ways for – Online modification – Maintenance of quality of service while providing necessary flexibility – Creation and execution of policies and rules – Adaptation to users and contexts – Enabling of user-controlled orchestration
  20. 20. Ultra Large Scale Systems, York EngD programme, 2010 Slide 20 Monitoring and assessment • The effectiveness of ULS system design, operation, evolution, orchestration, and control has to be evaluated. • There must be an ability to monitor and assess ULS system state, behavior, and overall health and well being. • Challenges include – Defining indicators – Understanding why indicators change – Prioritizing the indicators – Handling change and imperfect information – Gauging the human elements
  21. 21. Ultra Large Scale Systems, York EngD programme, 2010 Slide 21 Reductionist view of research
  22. 22. Ultra Large Scale Systems, York EngD programme, 2010 Slide 22 Post-reductionist research
  23. 23. Ultra Large Scale Systems, York EngD programme, 2010 Slide 23 ULSS research areas • Human interaction • Computational emergence • Design • Computational engineering • Adaptive system infrastructure • Adaptable and predictable system quality • Policy, acquisition and management
  24. 24. Ultra Large Scale Systems, York EngD programme, 2010 Slide 24 Conclusions • There is an unstoppable trend toward increasing scale in many systems important to our society. • Scale changes everything. Manifestations of scale and its attendant complexity arise in many disciplines, and can be understood as a phenomenon in its own right. • New, interdisciplinary perspective and new research in building ultra large-scale systems is long overdue. • “Since computation has moved over the past twenty years decisively closer to people, interfaces with social sciences such as Psychology and Sociology, besides Economics, have become increasingly important” – Christos H. Padadimitriou, in “Algorithms, Games, and the Internet”
  25. 25. Ultra Large Scale Systems, York EngD programme, 2010 Slide 25 Conclusions • What you call a system (system of systems, ULS system, complex net-centric system, LSCITS) is really unimportant. • It is important that ULS system characteristics are recognized. – These characteristics undermine the assumptions we make in most current technical, management, and acquisition approaches. – The ULS system perspective is helpful in understanding some of the current technology and management shortcomings and issues with system of systems.

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