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Chapter 3 - Modeling and Process Modeling1 Chapter 3 – Modeling and Process Modeling By Dr. Sartuk KARASOY Middle East Technical University skarasoy@metu.edu.tr The viewgraphs are mainly courtesy of Dr. Dennis Buede. Aerospace Systems Engineering

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Chapter 3 - Modeling and Process Modeling2 Models Incomplete representation of reality Answers questions Types of questions –Definitional (inputs, outputs, functions) –Descriptive, predictive –Normative (decision making mechanism)

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Chapter 3 - Modeling and Process Modeling3 Taxonomy of Models Model Categories Model Subcategories Typical Systems Engineering Questions PhysicalFull-scale mock-up Subscale mock-up Breadboard How much? How often? How good? Do they match? QuantitativeAnalytic Simulation Judgmental How much? How often? How good? QualitativeSymbolic Textual Graphic What needs to be done? How well? By what? MentalExplanationAll of the above! Table 3.1

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Chapter 3 - Modeling and Process Modeling4 Modeling Languages Semantics: signs and symbols Syntax: way in which signs and symbols are put together “A map is not the territory that it represents.”

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Chapter 3 - Modeling and Process Modeling5 CORE System & Process Models ER --> Relationship FFBD/EFFBD --> Functional N 2 --> Interface, Data Flow Hierarchical --> Physical, Tracebility IDEF0 --> Functional, Organizational

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Chapter 3 - Modeling and Process Modeling6 Model Development Process Questions to be answered Modeling method selection Design, test and refinement Validation –Conceptual (theory and assumptions) –Operational (output behavior) –Data (inputs for design, test and use) Analogy with System Development Process

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Chapter 3 - Modeling and Process Modeling7 IDEF0 Genesis: Air Force’s Integrated Computer- Aided Manufacturing (ICAM) program Variation of Structured Analysis & Design Technique (SADT), SofTech - David Ross ICAM Definition Integrated Definition for Function Modeling (by: Air Force Wright Aeronautical Lab)

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Chapter 3 - Modeling and Process Modeling8 IDEF Family of Methods

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Chapter 3 - Modeling and Process Modeling9 IDEF0 Semantics & Syntax Model –Semantics: Collection of pages –Syntax: Hierarchical structure Page –Semantics: Boxes and arrows Boxes: Functions, processes, activities Arrows: Flow of material or data –Inputs enter from left –Controls enter from top –Outputs leave from right –Mechanisms enter from bottom –Syntax: Interaction of functions via material & data Transforms inputs into outputs Using guidance of controls As performed by mechanisms Figure 3.1, 2 ICOM

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Chapter 3 - Modeling and Process Modeling10 IDEF0 Model Answers definitive questions about the transformation of inputs into outputs by the system Establishes the boundary of the system on the context page. This boundary is explicated, if needed, as a meta description. Has one viewpoint; the viewpoint is the vantage or perspective from which the system is observed. Is a coordinated set of diagrams, using both a graphical language and natural language.

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Chapter 3 - Modeling and Process Modeling11 IDEF0 Rules & Guidelines Rules –Conservation of inputs, controls, outputs & mechanisms –Every function has a control and output Guidelines –3 to 6 functions per page arranged diagonally –Control-oriented functions placed at top left –Major output functions placed on bottom right –Arcs & functions are decomposable –Feedback is defined by arcs moving from bottom right to top left

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Chapter 3 - Modeling and Process Modeling12 Arrow Semantics Figure 3.3

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Chapter 3 - Modeling and Process Modeling13 Feedback Semantics of Functions Figure 3.4

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Chapter 3 - Modeling and Process Modeling14 IDEF0 Page Structure Page Number(s)Page Content A - 1Ancestor or external system diagram A - 0Context or system function diagram (contains A0) A0Level 0 diagram with first tier functions specified A1, A2,...Level 1 diagrams with second tier functions specified A11, A12,..., A21,... Level 2 diagrams with third tier functions specified...… Figure 3.5; Table 3.2

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Chapter 3 - Modeling and Process Modeling15 IDEF0 Functional Decomposition Figure 3.6

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