Ultra-large Scale Systems (LSCITS EngD 2011)

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

Ultra Large Scale Systems

Ian Sommerville


Objectives

•  To discuss the notion of ULSS systems��

•  To introduce the SEI study report on ULSS


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.


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


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


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


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


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


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


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


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.


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.


Systems as buildings


ULSS as cities


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?


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.


Central challenges of ULSS

•  Design and evolution

•  Orchestration

•  Monitoring and assessment

•  Organizational integration

•  Regulation and control


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


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


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


Reductionist view of research


Post-reductionist research


ULSS research areas

•  Human interaction

•  Computational emergence

•  Design

•  Computational engineering

•  Adaptive system infrastructure

•  Adaptable and predictable system quality

•  Policy, acquisition and management


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”


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.

Technology

Ultra-large Scale Systems (LSCITS EngD 2011)