1. Ch 2 Structure of Complex System
Bassam Odeh
Bassam Odeh

2. Introduction
System Engineer raises the question of how deep that understanding of a broad knowledge needs to be in the development of a complex system
System Engineer must recognize such factors as program risks, technological performance limits, and interfacing requirements, and make trade-off analyses among design alternatives.
System building block provide an important insight by examining the structural hierarchy of modern systems.
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3. System Complexity What Makes a System Complex?
How does Complexity evolve?
What are the ways of dealing with Complexity?
Are we gaining or losing?
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4. What Characterizes Complexity?
Complex: composed of interconnected or interwoven parts.
Does not stipulate the number of interconnected parts. A complex system may consist of a small number of parts connected in complicated ways.
A large number of disconnected parts is not complex system, for example a large collection of books.
The items that distinguish a complex system from a collection of parts are the connections.
The manifestation of a complex system is the dependence upon the interfaces.
Different configurations of interfaces lead to much different systems, different arrangements of parts constitute the same collection
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5. What Makes a System Complex?
Impossible for an individual to comprehend all of the design; exceeds human intellectual capacity
Complexity is Inherent, not Accidental
Complex problem domains
Needs and requirements change and evolve
Difficulty expressing needs and requirements
Expansion of previous system
Difficulty managing development
Systems are becoming increasingly large & complex
Coordination of large team efforts very costly
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6. What Makes a System Complex (cont’d)?
Human Limitations
Fundamental single-channel processing speed limits (order: 40 bytes/sec, 5 secs/“chunk”)
Fundamental limit to parallel processing (order 7)
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7. Examples of Complexity
PC: hierarchic decomposition
Structure of plants and animals: cellular systems
Structure of matter: electrons, protons, neutrons (quarks)
Structure of business systems
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8. Subdividing Complexity
Simplification Approaches
Decomposition:
Algorithmic imperative: by progressive steps in a hierarchical process
Object-oriented: by tangible entities which exhibit well-defined behaviors
Abstraction:
Extraction of essential elements
Inherent in models and modeling
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9. Decomposition Complex Systems  decomposition
How decompose, lots of ways, pending idea?
Where do you “cut”?
Decomposition is hierarchical; what defines the levels & depths?
Align with specialties, functional vs. physical?
Every cut creates an interface
What are the characteristics of the interfaces (internal/external), complexity, testability, responsibility?
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10. Decomposition (cont’d)
Optimality
What constitutes the “best” decomposition?
What is good enough?
How do we recover from a bad choice?
What are the implications for integration & testing?
How do we handle testing of internal interfaces?
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11. Are We Gaining or Losing?
Arguably, hardware capabilities are increasing at an
exponential rate.
Software is becoming a larger part of modern systems than
it has been in the past and software is more complex
and more “opaque.”
Technology is compounding with complex systems being
embedded in other complex systems.
Systems engineering practices and procedures and products
appear to be evolving at a much slower rate.
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12. Hierarchy of Complex Systems
• Model of Complex System:
- Consists of a number of major interacting elements
- Majority of systems are developed by an integrated acquisition
process
• Definition of System Level:
- System → Subsystems → Components → Subcomponents → Parts
: System – serves as parts of more complex aggregates or super-systems and perform a significant useful service with only the aid of human operators and standard infrastructure ( e.g. highways, fueling stations, communication lines, etc)
: Subsystem- performs a closely related subset of the overall system functions
: Component- refer to a range of mostly lower level, middle of system level
: Parts- perform in combination with other parts
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13. System Design Hierarchy
Model of Complex System : System, Subsystem, Component, Parts
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14. System Engineer vs. Design Specialist
• System Engineer’s Domain:
- Extends down through the component level
- Is as detailed as a system engineer usually needs to go
- Extends across several system categories
• Design Specialist’s Domain
- Extends from the part level up through the component level
- Overlaps the domain of the systems engineers
- Is usually limited to a single technology/discipline
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15. System Engineer vs. Design Specialist
Knowledge domain of systems engineer and design specialist
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16. System Building Blocks
Methods of Functional Design
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17. System Building Blocks with Elements
• Basic building blocks of all engineered systems
. Characterized by functional and physical attributes
. Significant, performing a distinct and significant function
. Singular, within the scope of a single engineering discipline
. Common, with functions founded in a variety of system types
• Functional Building Block- elements:
- Functional equivalents of components, four classes by medium
. Signal element: sense and communicate information
. Data element: interpret, organize, and manipulate information
. Material element: provide structure and process materials
. Energy element: provide energy and power
• Physical Building Block- elements:
. Electronics, Electro-Optical, Electro-mechanical, Mechanical, Thermomechanical, Software
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18. System Decomposition External Systems Domain of the
Enterprise
System/
Functional Options
Domain of the
Systems Engineering
Subsystem
Component/
Building Blocks
Subcomponents
Domain of the
Technical Specialist
Parts
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19. Developmental Options
Derived from predecessor system
largely deductive, straightforward
may be sub-optimal
Derived from past experience with other systems
may lack appropriate experience
likely to be sub-optimal
Composed “bottom up” from Building Blocks
largely deductive
structured
weakly constrained
“Imagineering”
unstructured, inductive
unconstrained
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20. Building Blocks –The Concept
A library of commonly occurring system elements
A means for classifying system constituents according to:
functional characteristics
physical characteristics
A useful tool for modeling system architecture and its synthesis
Useful for visualizing potential architectures of system concepts
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21. Functional Categories
Signals Material
generate, modify, support, transform,
transmit, distribute shape, alter
composition, alter location
Data Energy
develop, distribute, transmit, convert, receive
analyze, store, convert
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22. Signal Functional Elements
Functional Element Physical Examples
Input signal TV camera, FAX, scanner
Transmit signal Radio transmitter, audio amplifier
Transduce signal Antenna, sonar
Receive signal TV tuner
Process signal Image processor, filter
Output signal TV display, speaker
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23. Data Functional Elements
Functional element Physical Examples
Input data Keyboard, modem
Process data CPU, parallel processor
Control system DOS, UNIX
Control Processing Word Processor, analysis program
Store data Magnetic disk
Output data Printer, display
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24. Material Functional Elements
Functional element Physical Examples
Support material Airframe, auto body
Store material Container, enclosure
React material Autoclave, smelter
Form material Milling machine, foundry
Join material Welding, riveting
Control position Auto tool feed, power steering
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25. Energy Functional Elements
Functional element Physical Examples
Generate thrust Rocket, turbojet
Generate torque Gas turbine
Generate electricity Power plant, solar cells
Control temperature Furnace, refrigerator
Control motion Transmission, power brakes
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26. System Functional Elements
Functional Element: Signal, Data, Material, Energy
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27. Physical Building Blocks
Category Component Examples
Electronic Receiver, transmitter
Electro-optic Optical sensing, fiber optics
Electro-mechanical Electric generator, data storage,
transducer
Mechanical Container, material processor,
material reactor
Thermo-mechanical Jet & rotary engine, Heating & AC
Software Operating system, applications firmware
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28. Physical Building Block
Physical Elements: Electronics, EO, EM, Mechanics, TM, Software
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29. Application of System Building Block
- Identifying actions capable of achieving operational outcomes
- Facilitating functional partitioning and definition
- Identifying subsystem and component interfaces
- Visualizing the physical architecture of the system
- Suggesting types of component implementation technology
- Helping software engineers acquire hardware domain knowledge
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30. System Environment – outside the system
- System operators, Maintenance, Housing, and Support Systems
- Shipping, Storage, and Handling
- Weather and other physical environments
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31. Current Systems and Building Blocks
Systems can generally be subdivided into three major components:
hardware, software, and human-computer interfaces (HCI).
Hardware: most hardware systems and components are already
thought of in terms of components, innovative designs may
be.
Software: most software is NOT constructed from building blocks.
A relatively new field called Patterns is an attempt to develop
software building (beyond the scope of this course).
HCI: HCI is composed of hardware and software and reflects
the comments above. Conceptually, HCI does not have
many building blocks yet.
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32. Summary of Building Blocks
Provides a structured view of the necessary knowledge base for systems engineers
Provides a mechanism for deductive decomposition of functional architectures to components
Provides a structured view of a wide variety of systems
Provides ingredients for modeling system architecture
Provides a strong link to the concept of object-oriented design
Building Blocks are fundamental to the concept of modularization, which in turn, is fundamental to successful system design.
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33. System Environment- Example
-System operators, Maintenance, Housing, and Support Systems
-Shipping, Storage, and Handling, Weather and physical environments
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34. System Interface and Interactions
System Interface are a critical systems engineering:
- Effect interactions between components
- Require identification, specification, coordination, and control
- Require that test interfaces be provided for integration and
maintenance
- Include elements that connect, isolate, or convert interactions
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35. System Interface - Example
Functional Interface and Physical Interfaces
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36. Chapter 2 Summary
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37. Complex Systems
Complex Systems may be represented by a hierarchical structure in that they are composed of parts, subcomponents, components, and subsystems
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38. Systems Engineer Domain
The domain of systems engineering:
Extends down through the component level
Is detailed as a systems engineer usually needs to go
Extend across several system categories
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39. Design Specialist Domain
The domain of the design specialist
Extend from the part up through the component level
Overlaps the domain of the systems engineer
Is usually limited to single technology/discipline
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40. System Building Blocks – Component Level
System Building Blocks are at the level of components and are:
The basic building blocks of all engineered systems
Characterized by both functional and physical attributes
Significant, performing a distinct and significant function
Singular, within the scope of single engineering discipline
Common, with functions found in a variety of system types
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41. Functional Elements Categories
Functional elements are functional equivalents of components and are categorized into four classes by operating medium:
Signal elements, which sense and communicate information
Data elements, which interpret, organize, and manipulate information
Material elements, which provide structure and process material
Energy elements, which provide energy or power
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42. Physical Components Categories
Components are physical embodiment of functional elements, which are categorized into six classes by materials of construction:
Electronics
Electro-Optical
Electromechanical
Mechanical
Thermo-mechanical
Software
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43. System Building Blocks Benefits
System building blocks models can be useful in:
Identifying actions capable of achieving operational outcomes
Facilitating functional partitioning and definition
Identifying subsystem and component interfaces
Visualizing the physical architecture of the system
Suggesting types of component implementation technology
Helping software engineers acquire hardware domain knowledge
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44. System Environment
The system environment, that is everything outside the system that interacts with it, includes:
System operator (part of the system function but outside the delivered system)
Maintenance, housing, and support systems
Shipping, storage, and handling
Weather and other physical environments
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45. Interfaces Critical Systems Engineering Concern
Interfaces are a critical systems engineering concern, which:
Effect interactions between components
Require identification, specification, coordination, and control
Require that test interfaces be provided for integration and maintenance
Include elements that connect, isolate, or convert interaction
Bassam Odeh