1. 1 Introduction to Complex Systems: How to think like nature Russ Abbott Sr. Engr. Spec. Rotn to CCAE 310-336-1398 Russ.Abbott@Aero.org  1998-2007. The Aerospace Corporation. All Rights Reserved. Design: platforms and levels of abstraction

2. 2 Complex systems: How to think like nature Unintended consequences. Emergence: what’s right and what’s wrong with reductionism. Design: levels of abstraction/platforms. Evolutionary processes, genetic algorithms, and entities as nature’s memes. Wisdom of crowds: hierarchy, autonomy, commons, C2. Externalizing thought Feasibility ranges (vs. engineering margins) Simulations: floor and noticing emergence. Computer Science vs. Engineering

3. 3 Complexity typically involves multiple autonomous components Poincare showed a century ago that the three-body gravitational problem has no general solution. Distributed software is the most difficult to write. Making effective use of multi-core computers will be the computing challenge of the next decade. Recall the ants and termites; the snake control authority and the snake farmers. All are multi-agent. Command and Control (or organization management) is still more art than science. All this contrasts with monolithic top-down control. Wikipedia commons When multiple autonomous entities interact within an environment, one often gets emergent results. Systems of that sort tend to be called complex. } Imagine having to program the Game of Life. Derogatory terms in the complex systems world Power to the edge!

4. 4 Try it out File > Models Library > Biology > Termites Click Open

5. 5 Three tabs Interface tab: control the model. To run most models, press setup and then go. Press go again to stop the run. Information tab: documentation about the model Procedures tab: the model in NetLogo code Online guide: http://ccl.northwestern.edu/netlogo/docs/

6. 6 Termite rules Wander about aimlessly (randomly) until you bump into a wood chip. –If you are not holding a wood chip Pick up the new chip. Move away from your current location. Go back to wandering about aimlessly. –If you are holding a wood chip Put down your held chip in a nearby empty space. Move away from your current location. Go back to wandering about aimlessly. Net effect: wood chips are deposited near other wood chips, eventually forming a single pile. Wikipedia commons Run the program and watch what happens. Exercise: prove that this will always happen

7. 7 Reading the code: the Procedures tab to go search-for-chip find-new-pile put-down-chip end to search-for-chip ifelse pcolor = yellow [ set pcolor black set color orange fd 20 ] [ wiggle search-for-chip ] end to find-new-pile if pcolor != yellow [ wiggle find-new-pile ] end to put-down-chip ifelse pcolor = black [ set pcolor yellow set color white get-away ] [ rt random 360 fd 1 put-down-chip ] end to get-away rt random 360 fd 20 if pcolor != black [ get-away ] end to wiggle fd 1 rt random 50 lt random 50 end

8. 8 Group-level emergence Both the termite and ant models illustrate emergence (and multi- scalarity). In both cases, individual, local, low-level rules and interactions produce “emergent” higher level results. –The wood chips were gathered into a single pile. –The food was brought to the nest. Ant and termite colonies may seem different from E. coli because we see them as groups of individual entities, often called agents. But emergence as a phenomenon is the same. In both cases we can explain the design of the system, i.e., how the system works. In Evolution for Everyone, David Sloan Wilson argues that all biological and social elements are best understood as both groups and entities. http://evolution.binghamton.edu/dswilson/

9. 9 Breeding groups/teams Chickens are fiercely competitive for food and water. Commercial birds are beak-trimmed to reduce cannibalization. Breeding individual chickens to yield more eggs compounds the problem. Chickens that produce more eggs are more competitive. Instead Muir bred chickens by groups. At the end of the experiment Muir's birds' mortality rate was 1/20 that of the control group. His chickens produced three percent more eggs per chicken and 45% more eggs per group. Traditional evolutionary theory says there is no such thing as group selection, only individual selection. Bill Muir (Purdue) demonstrated that was wrong. Evolutionary processes are fundamental to complex systems Wikipedia commons http://www.ansc.purdue.edu/faculty/muir_r.htm

10. 10 Emergence demystified As we said earlier, emergence is simply the consequence of a design, i.e., components interacting. The design might be –naturally arising, i.e., created and forged by evolution –man-made. It might relate components of what would normally be considered an entity. –The emergent property is at the entity level. –In might be mechanical, e.g., a clock with lots of gears. Or, it might relate “agents” interacting as part of what would normally be considered a collective. –The emergent property is at the collective level. Emergence doesn't necessarily imply a complicated system. Emergence: the existence of a phenomenon that can be described independently of its implementation.

11. 11 One more—because it’s so famous File > Models Library > Social Science > Segregation Click Open

12. 12 Credited with being the first agent-based model Reasonable micro-level preferences produce macro-level segregation. Each agent wants the percentage of like agents to be as indicated in %-similarity wanted. –Similar agents/total agents. Empty neighbors ignored. Starts out at ~50% similar since scattered at random. But some are unhappy. They move to a random empty spot. Repeat until all agents happy. Easier to see if more agents. Set number to 2500 agents. 30%-similarity-wanted produces 75% similarity. 40%-similarity-wanted produces 80% similarity. Try this. Set %-similarity-wanted to 75%. (Ethnic cleansing!) At about 2% unhappy, set it to 76%. Switch back and forth. An artifact of the model.

13. 13 Lots of artifacts Counts only 8 neighbors. Can mitigate clustering (and produce stripes at 30%-similar-wanted) by adding one line. to update-turtles ask turtles [ ;; in next two lines, we use "neighbors" to test the eight patches ;; surrounding the current patch set similar-nearby count (turtles-on neighbors) with [color = [color] of myself] set other-nearby count (turtles-on neighbors) with [color != [color] of myself] set total-nearby similar-nearby + other-nearby set happy? similar-nearby >= ( %-similar-wanted * total-nearby / 100 ) and other-nearby >= ( %-similar-wanted * total-nearby / 200 ) ] end Sets non-similar requirement to be half as many as similar requirement. Want a separate slider for %-other-wanted?

14. 14 More emergence: a satellite in a geostationary orbit The satellite is fixed with respect to the earth as a reference frame. But nothing is tying it down; no cable is holding it in place. Wikipedia commons period of the orbit = period of the earth’s rotation Mechanism: ?Function: ?Purpose: ? This example is typical of complex system mechanisms. Multiple independent or quasi-independent processes — which are not directly connected causally — interact within an environment to produce a result. In some ways the simplest possible complex system.

15. 15 4.2.4.2. Logical Analysis The design approach resulting from Logical Analysis: –Partitions a system into self-contained, cohesive, logical groupings of interchangeable and adaptable elements to enable ease of change, achieve technology transparency, and mitigate the risk of obsolescence; and –Uses rigorous and disciplined definitions of interfaces and, where appropriate, defines the key interfaces within a system by widely supported standards (including interface standards, protocols, and data interchange language and standards) that are published and maintained by recognized standards organizations. Traditionally, the Department of Defense has used functional analysis/allocation. However, other approaches, such as behavioral analysis, timeline analysis, object-oriented analysis, data-flow analysis, and structured analysis, may also apply. Defense Acquisition Guidebook

16. 16 4.2.4.5. Integration Integration is the process of incorporating the lower-level system elements into a higher-level system element in the physical architecture. –The plan or strategy for the Integration process, including the assembly sequence, may impose constraints on the design solution. –An assembled system element, also developed with the technical and technical management processes, may include fixtures for hardware or compilers for software. Integration also refers to the incorporation of the final system into its operational environment and defined external interfaces. Interface Management plays an important role with Integration, and iteration between the two processes will occur. Defense Acquisition Guidebook

17. 17 What one has at the end How does one know one can build these pieces? What enables the interfaces? What holds it all together? The unasked questions

18. 18 The unasked questions How do we come up with the pieces? –Do we invent them ab initio? This would be pure top-down engineering. We don’t do that. –We generally copy and modify something done already. –If possible we use standard parts. How do we know they can talk to each other? –They are assumed to be embedded in a framework that enables communication. –The framework may be very primitive, e.g., a world that can support wires. But there is an assumed framework. What holds it all together? –Again, they are assumed to be embedded in a framework. Bottom-up One can’t avoid bottom-up design.

19. 19 Bottom-up doesn’t mean That one gives up abstractions. –Emergence provides abstractions That one gives up components –Instances of emergence (entities) are components. That one gives up design –Emergence is the result of design

20. 20 Bottom-up does mean That one builds up from what exists That one factors out commonalities. E.g., the creation of subprograms was a factoring out of the practice of factoring out pieces of code. It moved that piece of functionality to a lower level of abstraction. That one creates and uses platforms. –The DNA-to-protein mechanism is a platform. –It is used to generate lactase in the same way it generates lots of other proteins. –It is extended with switches to make it more controllable. How does mail get delivered? –Postal service doesn’t have its own fleet or airplanes –It has its own fleet of cars, but it doesn’t build its own roads.

21. 21 More emergence: E. coli (again) E. coli has genes to produce lactase, which digests lactose. But it should produce lactase only when lactose is present. Imagine that you were asked to design a system that would produce a product only under certain conditions. How would you do it?

22. 22 A (quasi-top-down) functional analysis solution Lactose sensor How does one know one can build these pieces? What enables the interfaces? What holds it all together? The unasked questions Lactase production system Switch Off On Is it really top-down?

23. 23 Let lactose flip its own switch Lactose Repressor Lactose itself binds to the repressor, pulling it out of the way. lacYlacAlacX RNAP Repressor Three lac genes RNA polymerase can’t bind to DNA. Transcription blocked. lacYlacAlacX RNAP lac operon It’s often said that a first step in systems engineering is to agree on the system boundaries. What are the system boundaries in this case? It’s often said that a first step in systems engineering is to agree on the system boundaries. What are the system boundaries in this case? See movie http://www.biologycorner.com/bio4/notes/gene-expression.php.http://www.biologycorner.com/bio4/notes/gene-expression.php How does one know one can build these pieces? What enables the interfaces? What holds it all together? The unasked questions Nature is notoriously bottom-up Lactose Repressor lacYlacAlacX RNA polymerase can now bind to DNA. Transcription enabled. The genes are expressed. RNAP

24. 24 How does Aerospace deliver internal mail between El Segundo and Chantilly? El Segundo mail routes (carts) Chantilly mail routes (carts) LAX ↔ IAD (commercial aircraft) Aerospace USPS (trucks) Sort & route Many interlinked processes. The various systems provide platforms for each other. Infrastructure A system of (many!) systems. Aerospace, USPS, commercial airlines, airports, traffic, road maintenance, … A system of (many!) systems. Aerospace, USPS, commercial airlines, airports, traffic, road maintenance, …

25. 25 Designing an organism First arose in evolutionFunction Three billion years ago, in early prokaryotic organisms Energy metabolism, biosynthesis of 60 building blocks, DNA replication, DNA → RNA → protein, membranes, trans-membrane transport Two billion years ago, in early eukaryotic cells (with cell nuclei) Microfilaments and microtubules, cytoskeletons, motor proteins for internal transport, motility by cilia and ruffling, sexual reproduction One billion years ago, in early multi-cellular organisms Multi-cell signaling, cell adhesion, cell specialization Near pre-Cambrian, in animals with early body axes Complex developmental patterning, complex cell competence, additional specialized cell types, body plan and compartments. Everything elseDone mainly with gene switches.

26. 26 Use software as example of bottom-up Components (data bases) Libraries (math library) Platforms (languages, operating systems, browsers, messaging systems, … )

27. 27 Exploratory behavior Blood vessels. Nerve cells. Microtubules. In all these examples (and others), large numbers of variations are generated, which explore various parts of a space. Some establish themselves as a result of finding a stabilizing area. Others die back. The established ones become a basis for further development. Evolution may be reformulated in these terms. What gets established is the process of reproduction. The same picture can be painted of markets. What gets established is the transmission of product from producer to consumer and of payment from consumer to producer. An environment is innovative when it supports such exploration and process establishment.

28. 28 Evolution as exploratory processes Normally one thinks of evolution as random generation followed by selection. This view thinks of evolution as random exploration followed by establishment. What gets established are processes—which are then available to be built upon. Processes required energy to run them. –May be intrinsic (rapid transit; users pay for service) or extrinsic (freeway system; users provide the service for themselves). But essentially the same process: transportation. –Generally require a skeleton on which to operate.

29. 29 The V-model of systems engineering Validate the system Verify the system Verify Integrate and test Design and develop

30. 30 The implicit and unexplained steps Validate the system Verify the system Verify Integrate and test Design and develop

31. 31 The two sides are very different Work product: Designs and plans, i.e., abstractions. Work product : The physical product The result is the entire product. Not important how it is put together, only that it is. But the process of putting the pieces together is often quite delicate. Some pieces can’t be added before others are in place. Timing and ordering (inside- to-out or outside-to-in) are often critical in developmental processes. The result is the entire product. Not important how it is put together, only that it is. But the process of putting the pieces together is often quite delicate. Some pieces can’t be added before others are in place. Timing and ordering (inside- to-out or outside-to-in) are often critical in developmental processes. Finished designs include all levels. Not important the order in which the design elements are developed, only that they work. Each portion of the design is generally based on existing experience and known capabilities. Bottom-up and incremental from experience, not necessarily from structure. Finished designs include all levels. Not important the order in which the design elements are developed, only that they work. Each portion of the design is generally based on existing experience and known capabilities. Bottom-up and incremental from experience, not necessarily from structure.

32. 32 Design artifacts. Also used for maintenance Construction: process common resources/platforms Building Elevations, building plans, schedules, etc. Follow the plans to build the building: foundation and skeleton inward to details. Electrical/heating/plumbing/etc. built into walls. Major system Design documents. “Snap” components together to integrate: from details outward to entire system? Communication networks built as subsystems. Biological organism DNA. HOX genes control the developmental process. (Evo-devo: evolution mainly modifies development—slow.) “Run” the DNA to build the organism: skeleton inward to details. Internal connective systems (circulation and nerves) grow by exploration. Social, economic, ecological systems: Wikipedia Evolving (disorganized) descriptions of code, conventions, and practices. Often in people’s minds. Continually re-design and re-build all levels of the system while in use. The two sides of the V merge. Platforms (the wiki, website, and social structure) are the most stable elements. Install and test the carpets for durability. Buy and test the visible electrical and plumbing fixtures: lighting, sinks, faucets, etc. Buy and paint the drywall. Test for wear-resistance, cleanability, etc.. Nail the drywall to the studs wall-by-wall. Test for sturdiness, shear strength. Plug the walls together to make rooms. Verify the rooms: kitchen, bedroom, etc. Install items (stove, sinks, toilets, showers, lighting, etc.) in rooms. Test. Plug the rooms together to make floors. Verify the floors: main, living quarters, etc. Plug the floors together to make the building. Verify the building’s structural integrity. Build the plumbing network of pipes. Test the pipes. Build the electrical network of wires. Test the wires. Build the heating and air-conditioning network of ducts. Test the ducts. Wire/plumb the plumbing and electrical fixtures into their respective networks. Test. Pour the foundation. Test. Insert the plumbing, electrical, and heating/AC networks into the building. Verify. Attach the building to the foundation. Validate the building. Install and test the carpets for durability. Buy and test the visible electrical and plumbing fixtures: lighting, sinks, faucets, etc. Buy and paint the drywall. Test for wear-resistance, cleanability, etc.. Nail the drywall to the studs wall-by-wall. Test for sturdiness, shear strength. Plug the walls together to make rooms. Verify the rooms: kitchen, bedroom, etc. Install items (stove, sinks, toilets, showers, lighting, etc.) in rooms. Test. Plug the rooms together to make floors. Verify the floors: main, living quarters, etc. Plug the floors together to make the building. Verify the building’s structural integrity. Build the plumbing network of pipes. Test the pipes. Build the electrical network of wires. Test the wires. Build the heating and air-conditioning network of ducts. Test the ducts. Wire/plumb the plumbing and electrical fixtures into their respective networks. Test. Pour the foundation. Test. Insert the plumbing, electrical, and heating/AC networks into the building. Verify. Attach the building to the foundation. Validate the building.

33. 33 RedesignApplied at what level?Reconstruction Building New design elements derived from previous design elements and other developments in the world. Current building if new design is consistent with current design. Next building if new design requires restart. Remodel. Gut and rebuild? Tear back to usable framework. How far? What can be saved? Major system New design elements derived from previous design elements and other developments in the world. Current building if new design is consistent with current design. Next building if new design requires restart. Remodel. Gut and rebuild? Tear back to usable framework. How far? What can be saved? Block/version n+1 includes how much of block/version n? Biological organism “Run” the DNA to build the organism: skeleton inward to details. Internal connective systems (circulation and nerves) grow by exploration. Current entity if new design is consistent with current design, i.e., can be learned. Next entity if new design requires restart, i.e., new DNA. Social, economic, ecological systems: Wikipedia Continually re-design and re-build all levels of the system while in use. The two sides of the V merge. Platforms (the wiki, website, and social structure) are the most stable elements. Current culture if new design is consistent with current design. Next culture if new design requires restart.

34. 34 Types of dependencies/transformations Current generation: structure, maintenance, enhancement. –Depends on other design elements. A satellite depends on solar cells. –Capability depends on ability to adjust/extend current design: learning, training, ability to upload new modules, housekeeping maneuvers, … –Redesign without rebuilding: Wikipedia, anything that is backward compatible keeps current version of whatever the backwards compatibility supports. Next generation. –Version n+1 of a product/system. Possible to modify any part/level of the design as long as the rest can be adjusted to fit. –Exaptation of pre-existing design elements. Next generation. Bat wings, inner ear bones. Both resulted from modifying the developmental processes. The ability to talk was built upon breathing. Bacteria take control of inset hosts. Not clear how it works, but perhaps due to rigid control structures in insects. Wifi bridge depends on USB port for power. –Core-to-semiconductor memory. Platform.

35. 35 Advantage of an explicitly manipulable design New design elements are generally derived from previous design elements and must almost always make use of existing design elements. The new elements can be at any level, although the more basic the level, the more difficult it may be to use existing elements. A house can move from plaster to dry wall. It can replace fireplaces to central heat—and then central air. It can move from bricks to framing. It can move from high-usage to low-flush toilets. Some of these can be done to the existing house. Others require a completely new house. The change to the design does not necessarily parallel the change to the house in terms of the amount of change made (in terms of number of characters). That’s one of the benefits of a platform. It can be redesigned both above and below it. And if it’s a useful platform, it will encourage both productive use and productive re-implementation. Can go from pony express to airplane with virtually no change elsewhere.

36. 36 Modifications Biology: There is a programmable construction process that can be changed. But not on existing entities. Buildings: once built, the earlier the component, the harder to change. System: like buildings. Society: can always create more core elements and switch from one to another. Why is there so much flexibility? –Because we operate on more platforms than anyone else, from reality to symbolism.

37. 37 Designing a spacecraft Structures Attitude control Thermal control Energy access (solar panels) Internal communication (for housekeeping functions, etc.). Bus. External communication Payload and payload processing If each of these were designed separately, i.e., really top-down, where would the satellite be?

38. 38 The difference between an interface and an API Interface - ICDAPI – conceptual model Specification levelLow level (signals)High level (functions) Communication levelLow: syntactic signalsHigh: semantic symbols StructureHard-wired; rigidLoose; flexible CouplingTight—because low levelLoose—because high level Example: OSI stackPhysical layerApplication layer Example: directionsSequence of left-right turns Map with pointers to start and end and highlighting over route. AdaptabilityFragile/brittleRobust/adaptable Moral: use the right layer for the message. Every layer is needed. Don’t use an interface when you need an API. Moral: use the right layer for the message. Every layer is needed. Don’t use an interface when you need an API. Similar to the reductionist blind spot. Unable to find an ICD description to pick on