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Complex Systems Engineering
SwE 488
Complexity in Nature
Prof. Dr. Mohamed Batouche
Department of Software Engineering
CCIS – King Saud University
Riyadh, Kingdom of Saudi Arabia
[email protected]
Outline
• Introduction
• Natural Complex Systems
•Natural Ants
•Termites
•Bees
•Neurons
•Immune System
•Better defense against predators
•Complexity in Life
• Conclusion
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Introduction
3
Introduction
• "An individual ant is not very bright, but
ants in a colony, operating as a collective,
do remarkable things.
• A single neuron in the human brain can
respond only to what the neurons
connected to it are doing, but all of them
together can be Albert Einstein."
By Deborah M. Gordon (Stanford University)
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Complex Systems
• Complex systems are systems that
exhibit emergent behavior:
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Anthills
Human societies
Financial Markets
Climate
Nervous systems
Immune systems
Human societies
Cities
Galaxies
Modern telecommunication infrastructures
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Natural Complex
Systems
Bottom-up behavior:
Simple agents following
simple rules generate
complex
structures/behaviors.
Birds
Flocking
Fish School
A termite "cathedral"
mound produced by a
termite colony: a
classic example of
emergence in nature.
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Natural Complex
Systems
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NATURAL
COMPLEX SYSTEMS
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Natural Ants
• Individual ants are simple insects with
limited memory and capable of performing
simple actions.
• However, an ant colony expresses a
complex collective behavior providing
intelligent solutions to problems such as:
• carrying large items
• forming bridges
• finding the shortest routes from the nest
to a food source, prioritizing food
sources based on their distance and ease
of access.
Natural Ants
• Moreover, in a colony each ant has its prescribed task,
but the ants can switch tasks if the collective needs it.
• Outside the nest, ants can have 4 different tasks:
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•
•
•
Foraging: searching for and retrieving food
Patrolling: looking for food supply
Midden work: Sorting the colony refuse pile
Nest maintenance work: construction and clearing of chambers
• An ant’s decision whether to perform a task depends on:
• The Physical State of the environment:
− If part of the nest is damaged, more ants do nest maintenance work to
repair it
• Social Interactions with other ants
How Do Social Insects
Achieve Self-organization?
• Communication is necessary
• Two types of communication:
• Direct: antennation, trophallaxis (food or liquid
exchange), mandibular contact, visual contact, chemical
contact, etc.
• Indirect: two individuals interact indirectly when one of
them modifies the environment and the other responds to
the new environment at a later time. This is called
stigmergy.
Natural ants: How do they do it?
• How do they know which task to perform?
• When ants meet, they touch with their antennae, that are
organs of chemical perception.
• An ant can perceive the colony-specific odor that all nest
mates share.
• In addition to this odor, ants have an odor specific to their
task, because of the temperature and humidity conditions
in which it works.
• So that an ant can evaluate its rate of encounter with ants
of a certain task.
• The pattern of interaction each ant experiences influences
the probability it will perform a task.
Natural ants: How do they do it?
• How can they manage to find the shortest path?
"The best possible way for ants to find anything
is to have an ant everywhere all the time, because
if it doesn't happen close to an ant, they are not
going to know about it. Of course there are not
enough ants in the colony, so the ants have to
move around in a pattern that allows them to
cover space efficiently"
Natural ants: How do they do it?
• They establish indirect communication system based on the
deposition of pheromone over the path they follow.
• An isolated ant moves at random, but when it finds a pheromone trail,
there is a high probability that this ant will decide to follow the trail.
• An ant foraging for food deposits pheromone over its route. When it
finds a food source, it returns to the nest reinforcing its trail.
• So, other ants have greater probability to start following this trail and
thereby laying more pheromone on it.
• This process works as a positive feedback loop system because the
higher the intensity of the pheromone over a trail, the higher the
probability of an ant start traveling through it.
Natural ants: How do they do it?
• The pheromone concentration
on trail B will increase at a
higher rate than on A, and
soon the ants on route A will
choose to follow route B
• Since the route B is
shorter, the ants on this
path will complete the
travel more times and
thereby lay more
pheromone over it.
• Since most ants will no longer
travel on route A, and since
the pheromone is volatile,
trail A will start evaporating
• Only the shortest route will
remain!
Natural ants:
(1)
•
Experiments
(2)
(3)
(1) Ants finished all
using the same path
(each one of the 2 paths,
50% of times)
• (2) Ants use the short
path
• (3) Ants get to find the
shortest path
(1)
(2)
Shortest path discovery
Ants get to find the shortest path after few minutes
…
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slides from EVALife
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Adaptive Path
Optimization
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slides from iridia.ulb.ac.be/~mdorigo
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Adaptive Path
Optimization
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Adaptive Path
Optimization
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slides from iridia.ulb.ac.be/~mdorigo
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Adaptive Path
Optimization
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slides from iridia.ulb.ac.be/~mdorigo
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TERMITES
CONSTRUCTION
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Termite Constructions
Termite mounds are often built
on a huge scale:
millions of builders
 thermoregulation, defence, agriculture, climate
control, créches, graveyards, even optimal
acoustic properties !!!!

What is more astonishing is that
the termites which construct these
nests are blind !!!


Termites
Cone-shaped outer walls
and ventilation ducts
Brood chambers in
central hive

Spiral cooling vents

Support pillars
Basic Mechanism
of Construction
(Stigmergy)
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Worker picks up soil granule
Mixes saliva to make cement
Cement contains pheromone
Other workers attracted by
pheromone to bring more
granules
• There are also trail and queen
pheromones
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Fig. from Solé &
Goodwin
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Termite Mounds
• Giant African fungus-growing
termites
build
a
high-rise
termitarium from dried mud-pellets,
which can be up to 26 feet high and
about
10ft
across.
These
‘skyscrapers’ are well ventilated
inside by a network of tunnels with
fresh air being drawn in through
nest walls and warm air rising from
below escapes outside through tall
‘chimneys,’ minute holes in the hard
surface.
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BEES
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Bees
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Colony cooperation
Regulate hive
temperature
Efficiency via
Specialization: division
of labour in the colony
Communication : Food
sources are exploited
according to quality
and distance from the
hive
Bees Colony
Three members of the colony
Worker
Queen
Drone
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Social behavior in Honey
Bees is highly organized
The Caste system is when a society has distinct groups
in the population that are designed for a particular
role.
Termites, ants and honey
bees have a caste system
which results in great
efficiency in food
collection, reproduction
and child rearing.
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Queen lays egg
in a brood cell
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Worker feeds
hatched larva
3 Larva
grows
4 Worker caps
cell
5
6
Larva spins
cocoon and
becomes
pupa
Adult bee
leaves cell
Communication is
important in a social
group!!
Worker honey bees communicate
by performing dances. The dance
performed indicates the direction
and distance of a good food
source.
Waggle Dance
Round Dance
The Round Dance
The Figure Eight or
Waggle dance
Indicates a food
source less than
90m away
Indicates a food
source more than
90m away with
direction
Waggle dance
Two components of the waggle dance
1. Straight run which indicates the
direction of the food according to
the angle of the waggle run on the
vertical surface. If the bee waggles
directly up the surface, then the
food source is directly toward the
sun. If the bee waggles directly
down the surface, then the food
source is directly away from the
sun. If the food source was located
90 degrees to the right of the sun,
the bee would waggle 90 degrees to
the right.
2. the speed at which the dance is
repeated indicates how far away the
food is
OUR BRAINS
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Our Brains
• ~100Bn neurons, each
with 10K neighbours
• 1000 trillion synapses
for a 3-year-old child
• Developmentally plastic
into adulthood
• + Chemical processes

Language, logic, emotion, cognition,
memory, learning, motor control,
consciousness, etc.
The Human Brain
• Made up of billions of neurons, each of which exhibits very simple
behavior, and single-bit memory. Some stochastic characteristics.
• Assessment: the top-level system (the brain, three pounds) displays
an infinitely sophisticated and complicated behavior: language,
visual, aural, and tactile I/O, the arts, culture, emotions, as well as
logical thought and processing. Robust, adaptive, innovative.
• A thorough scientific examination of the individual neurons would
not predict the behavior of billions of them working together.
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Typical Neuron
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IMMUNE SYSTEM
(COMPLEX ADAPTIVE SYSTEM)
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IMMUNE SYSTEM
(COMPLEX ADAPTIVE SYSTEM)
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Virus vs. Bacteria
• Colds are caused by a
virus, which is a nonliving
particle
that
contains
genetic
material, and hijacks
your cells to reproduce.
• Bacteria
are
living
organisms that can
reproduce on their own.
How does the body fight
infection/foreign invaders?
The Body has three lines of Defense:
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The Skin (Provides Physical and
Chemical barriers)
•
Nonspecific Immune Response
•
Specific Immune Response
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Nonspecific Immune Response
These are defenses the body uses no matter what
the invader may be. These defenses include:
• Phagocytosis – done by Macrophages
• Natural Cell Killers
• Inflammation - caused by release of Histamine from
leukocytes
• Fever – caused by histamines. The fever (high temp) kills
invaders by denaturing their proteins.
Macrophage: A phagocytic cell found in the liver, spleen, brain and
lungs. Travels to all areas of the body to find and eat pathogens.
Inflammatory Response
Inflammatory Response
Specific Immune
Response
This is a specific
response to a specific
pathogen/antigen.
• The response involves
the creation of
Antibodies
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Major players
• The major players in the immune system
include:
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•
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Macrophage (Phagocyte)
T cells (helper, cytotoxic, memory)
B cells (plasma, memory)
Antibodies
Some vocabulary:
• Antibody: a protein
produced by the human
immune system to tag and
destroy invasive microbes.
• Antigen: any protein that
our immune system
recognizes as “not self.”
(Infected cell, tagged
microbes, Cancer cell)
Antigen recognition
• Cells of the immune system are “trained” to
recognize “self” proteins vs. “not self” proteins.
• If an antigen (“not self”) protein is encountered by a
macrophage, it will bring the protein to a helper Tcell for identification.
• If the helper T-cell recognizes the protein as “not
self,” it will launch an immune response.
The Pathway of Specific Immune Response
Step 1
Pathogens eaten by
Macrophage
Step 2
Displays portion of
Pathogen on surface
Step 3
Pathogens
Helper-T cell
recognizes Pathogen
Helper T cells
• Helper T-cells have receptors for recognizing
antigens. If they are presented with an antigen,
they release cytokines to stimulate B-cell
division.
• The helper T-cell is the key cell to signal an
immune response. If helper T-cells are
disabled, as they are in people with AIDS, the
immune system will not respond.
Activates Cytotoxic
Activates B- Cell
T- Cell
Memory T-Cell
Kills Infected Cells
Memory B-Cell
Antibodies
B cells
• B-cells in general produce antibodies. Those
with antibodies that bind with the invader’s
antigen are stimulated to reproduce rapidly.
• B-cells differentiate into either plasma cells or
memory B-cells. Plasma cells rapidly produce
antibodies. Memory cells retain the “memory” of
the invader and remain ready to divide rapidly
if an invasion occurs again.
Clonal Selection
Role of antibodies
• Antibodies released into the blood stream will
bind to and deactivate the antigens that they
are specific for.
• Antibodies may disable some microbes, or cause
them to stick together (agglutinate). They “tag”
microbes so that the microbes are quickly
recognized by various white blood cells.
“Killer” T cells
• While B-cells divide and differentiate, so do
T-cells.
• Some T-cells become cytotoxic, or “killer” Tcells. These T-cells seek out and destroy any
antigens in the system, and destroy microbes
“tagged” by antibodies.
• Some cytotoxic T-cells can recognize and
destroy cancer cells.
Bring invader to helper T Cell
Lunch an immune response
Killer T Cell
Plasma cells rapidly produce
antibodies.
Calling a halt
• When the invader is destroyed, the helper
T-cell calls a halt to the immune
response.
• Memory T-cells are formed, which can
quickly divide and produce cytotoxic Tcells to quickly fight off the invader if it is
encountered again in the future.
Immune Response Summary
Displays copy of
antigen on surface
of cell
Antigen
Macrophage
Antibody Immunity
Helper T - Cell
Cellular Immunity
Active Cytotoxic T-Cell
Kills Infected Cells
Memory T- Cell
Active B - Cell
Plasma Cell
Antibodies
Deactivates Antigens
Memory B-Cell
Better defense against predators
(Cooperation & Co-Evolution)
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Avoiding Predation
• More compact aggregation
• predator risks injury by attacking
• Confusing predator by:
• united erratic maneuvers (e.g. zigzagging)
• separation into subgroups (e.g., flash expansion &
fountain effect)
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Flash Expansion
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Fig. from Camazine & al., Self-Org. Biol. Sys.
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Flash Expansion
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Fig. from Camazine & al., Self-Org. Biol. Sys.
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Fountain Effect
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Fig. from Camazine & al., Self-Org. Biol. Sys.
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Fountain Effect
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Fig. from Camazine & al., Self-Org. Biol. Sys.
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Fountain Effect
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Fig. from Camazine & al., Self-Org. Biol. Sys.
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Fountain Effect
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Fig. from Camazine & al., Self-Org. Biol. Sys.
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COMPLEXITY OF LIFE
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The Hydrologic Cycle
The Carbon Cycle
The Nitrogen Cycle
Conclusions
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Conclusions
• We can learn from nature and take advantage of
the problems that she has already solved.
• Many simple individuals interacting with each other
can make a global behavior emerge.
• Techniques based on natural collective behavior
are interesting as they are cheap, robust, and
simple.
• They have lots of different applications.
 Think Biology, Emergence, Complex Systems …
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References
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References
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2011.
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2011 .
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Pearson Education, Inc., 2006.
• Braha D., Minai A. A., Bar-Yam, Y. (Editors), Complex Engineered Systems, Springer,
2006
• Gibson, J. E., Scherer, W. T., How to Do Systems Analysis, John Wiley & Sons, Inc.,
2007.
• International Council on Systems Engineering (INCOSE) website (www.incose.org).
• New England Complex Systems Institute (NECSI) website (www.necsi.org).
• Rouse, W. B., Complex Engineered, Organizational and Natural Systems, Issues
Underlying the Complexity of Systems and Fundamental Research Needed To Address
These Issues, Systems Engineering, Vol. 10, No. 3, 2007.
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computing, Wiley, 2009.
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