1. Complex Systems Engineering SwE 488 System of Systems - SoS

2. System of systems
System: a collection of components organized to accomplish a specific function or set of functions (IEEE)
System-of-Systems: “a set or arrangement of systems that results when independent and useful systems are integrated into a larger system that delivers unique capabilities” [DoDDef. Acq. Guidebook 2004]
Emergent behavior, Evolutionary Development, Operational Independence of the Elements, Managerial Independence of the Elements, Geographic Distribution [Maier1996]

3. System of Systems – Intuitive sense
Intuitive sense of meaning of systems of systems
An arrangement of systems that enables achievement of a bigger and more interesting function than cannot be achieved by any of the component systems alone
This is insufficiently sophisticated to enable meaningful discussion of systems of systems design methods
I provide illustrations to enable thinking about the issues

4. Systems of Systems (example 1)
Prime system 4
Prime system 3
Prime system 1
Airport
Many systems arranged to give
meaning, purpose and
effectiveness to each system
Design of each complements the
others – deliberate development of
emergence
Prime system 2

5. System of Systems (example 2)
Traffic in a well ordered system
Users adhere to rules of use
Infrastructure design complements
Rules of use
Density of users
Outcome is orderly traffic

6. System of Systems (example 3)
Traffic in a poorly ordered system
Users do not adhere to rules of use
Design does not match actual use patterns
Outcome – 10 lane car park with 60mph limit!
Superficially similar to example 2

7. System of Systems (example 3)
Traffic in a poorly ordered system
Users do not adhere to rules of use
Design does not match actual use patterns
Outcome – 10 lane car park with 60mph limit!
Superficially similar to example 2
The cause of
the trouble

8. System of Systems (example 4)
Military expeditionary force
Army personnel and equipment delivered to a site by
Navy ship, all supported by
Air Force assets providing transport, support and surveillance
Assets not specifically designed to support each other
But within one nation it is reasonable to expect (at time of acquisition) that they may need to inter-operate
Coalition of nations
Not reasonable at time of acquisition to expect inter-operation
Potential issues of secrecy preventing design for interoperability – so the coalition is ‘come as you are’

9. So … What is A System of Systems?
A System of Systems (SoS) is a “super-system” made up of elements – each of which is itself a complex, independent system -- that interact to achieve a common goal.
SoS elements (i.e., the systems) can and do operate independently.
An SoS evolves – functions are added/removed/changed with experience.
An SoS exhibits emergent behavior not attributable to any element (system).
An SoS is geographically distributed – elements exchange information only.
-- Are These SoS? --
YES
YES
Systems-of-systems should be distinguished from large but monolithic systems by the independence of their components, their evolutionary nature, emergent behaviors, and a geographic extent that limits the interaction of their components to information exchange . ...
... Five principal characteristics are useful in distinguishing very large and complex but monolithic systems from true systems-of-systems.
Operational Independence of the Elements: If the system-of-systems is disassembled into its component systems the component systems must be able to usefully operate independently. The system-of-systems is composed of systems which are independent and useful in their own right.
Managerial Independence of the Elements: The component systems not only can operate independently, they do operate independently. The component systems are separately acquired and integrated but maintain a continuing operational existence independent of the system-of-systems.
Evolutionary Development: The system-of-systems does not appear fully formed. Its development and existence is evolutionary with functions and purposes added, removed, and modified with experience.
Emergent Behavior: The system performs functions and carries out purposes that do not reside in any component system. These behaviors are emergent properties of the entire system-of-systems and cannot be localized to any component system. The principal purposes of the systems-of-systems are fulfilled by these behaviors.
Geographic Distribution: The geographic extent of the component systems is large. Large is a nebulous and relative concept as communication capabilities increase, but at a minimum it means that the components can readily exchange only information and not substantial quantities of mass or energy.
Mark W. Maier, Architecting Principles for Systems-of-Systems, UA Huntsville, NO
Major League Baseball
Hardware
Oughta Be
International Air Travel
Joint Theater Ops
From INCOSE

10. Source: Monica Farah-Stapleton, IEEE SOS conference, 2006
Army SOS Perception

11. Emergence
EmergenceMacro level behaviors (patterns) that cannot be predicted from studying the micro level behaviors in isolation
Or the Whole is greater than the sum
Complex Systems of Systems composed of a (1) large number of entities, with (2) non-trivial interaction networks (not too simple or too complete) , whose (3) impacts on one another are non-linear, and whose overall behavior tends to display emergent characteristics

12. Characteristics of Emergence
System-level properties exist only at the system level as it functions, being
different from and existing beyond the constituent element, or subsystem,
properties.
System-level properties are not held by any of the isolated elements.
System-level properties are irreducible. They simply cannot be understood, explained, or inferred from the structure or behavior of constituent elements or their local properties.
Understanding cause–effect relationships can only be established through
retrospective interpretation. This renders traditional reduction-based analytic techniques incapable of useful predictions of emergent system-level behavior.

13. Principles of emergence
Condition of Emergence
An avalanche condition, or a critical state, has to exist prior to the occurrence of emergence.
Emergent behavior is inversely proportional to the degree of bondage between systems
– The more tightly the component systems are coupled
the less likely that the global emergent behavior will
prevail.
– Emergent behaviors do not arise in closed hierarchically structured systems.

14. Principles of Emergence (2)
Emergent behavior is non-linear
– Emergent behavior is more than the sum of added component systems.
– the output is not proportional to the inputs.
• Emergent behavior is self-organized
– Self-organization is a process in which the internal organization of a system, normally an open system, increases in complexity without being guided or managed by an outside source.
– This is a bottom-up process.

15. Examples of Emergence From Nature
• Crickets tend to synchronize their mating calls - calling all at once at the same speed.
Seasonal birds fly in large groups that seem to behave as one.
• The individual ants do not know about coordinated foraging; the hive as a whole knows.
consciousness is an emergent property of brains.

16. Computing Examples Ethernet capture effect Router Synchronization
Router periodically exchange protocol messages in huge amount
Floyd and Jacobson showed that in a network with “many apparently independent periodic processes ... these processes can inadvertently become synchronized”
The process is abrupt and large random components were needed to avoid synchronization
Ethernet capture effect
If A and B simultanously send packets collision will occur, Suppose that A chooses a smaller back off than B.
A always win because it reset timer and send and B get Worse
little extra delay was needed to insert to win
George Candea. Predictable Software – A Shortcut to Dependable Computing? Technical report, Stanford University, March

17. Misconfigured Load Balancer
multi-tiered distributed application, with numerous clients
Load balancer spread the load evenly and also detect the failure of App server
At some point, the system stops responding to requests.
the application servers are no longer responding to the load balancer within its configured timeout, and the load balancer ends up declaring both application servers dead.
one could argue that someone chose the wrong timeout for the load balancer, but that error might not have been obvious when the system was first tested

18. Internet Protocol
No IP router knows the complete topology of interconnections for the Internet or even the configuration of local interconnections in its own neighborhood
Configuration on router and bandwidth changes continuously
Still IP is reliable and efficient
Each IP router along the path of a message decides which of its immediate neighbor routers will constitute the next hop without knowledge of routers or likely paths beyond that immediate neighbor
IP routing emerges as reliable despite of incomplete, imprecise, and outdated information;

19. What is not Emergence
Single-component bugs that break the whole system
When critical part of system stop working
Inherently inefficient algorithms
Replicated file system that contacts replicas serially rather than in parallel will likely have sub-optimal performance.
Insufficient resources:
CPU, memory, network latency and bandwidth, storage capacity, latency, and bandwidth

20. Some research Questions
1.What is different about the nature of the SoS problem domain in contrast to more traditional problem domains? 2. How do philosophical, methodological, and axiomatic perspectives influence effectiveness in dealing with emergence in the SoS problem domain? 3. Given that emergence is going to occur in SoS, what are the implications for designing methodologies (approaches) that will enhance effectiveness in dealing with emergence? 4. What are the primary considerations that a designer of SoS should think about with respect to effectively dealing with emergence? 5. How might we assess the degree to which emergence is going to be problematic in an SoS effort? 6. What guidance for emergence might we give an engineering team getting ready to engage in an SoS problem?

21. Q & A