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Systems Engineering

Process Review

Mark E. Sampson

EMIS 8340

Systems Engineering Tool—applying tools to engineering systems

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SE Process

Problem Definition

FunctionalAnalysis

Systems Synthesis

Systems Analysis

DecompositionVerificationValidation

[Lacy 1992]

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Problem Definition

…includes requirement extraction, constraints, scope, environment, success criteria,…

Tools are used to capture the problem you are going to solve, what are the constraints, what are the external influencing factors, and how you know when you have arrived.

Problem Definition

FunctionalAnalysis

Systems Synthesis

Systems Analysis

DecompositionVerificationValidation

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Functional Analysis

…functional decomposition, sequence of events, interfaces,…

Tools are used to capture and analyze the functions to be performed by the system

Problem Definition

FunctionalAnalysis

Systems Synthesis

Systems Analysis

DecompositionVerificationValidation

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Systems Synthesis

…alternative development, configure components,…

Since there are an infinite number of possible solutions to a problem, tools are used to identify the constraints, and evaluate the alternatives that best meet the objectives

Problem Definition

FunctionalAnalysis

Systems Synthesis

Systems Analysis

DecompositionVerificationValidation

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Systems Analysis

…evaluate alternatives, choose solutions, optimization, sensitivity,…

Tools are used to evaluate solutions and how robust those solutions are to changing criteria

Problem Definition

FunctionalAnalysis

Systems Synthesis

Systems Analysis

DecompositionVerificationValidation

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Decomposition

…decompose requirements/functions, allocate requirements, decompose interfaces,…

Since very few systems are “single-layer”, tools help capture and decompose the system layer-by-layer as you work down through to the details

Problem Definition

FunctionalAnalysis

Systems Synthesis

Systems Analysis

DecompositionVerificationValidation

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Verification/Validation

…Verify that the correct set of requirements have been developed and validate they have been met…

Tools are used to capture, track, and document V&V efforts

Problem Definition

FunctionalAnalysis

Systems Synthesis

Systems Analysis

DecompositionVerificationValidation

System

Sub-System

Component

System

Sub-System

Component

Customer needs

CustomerValidation

Verification

The Product Development “V”

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Process vs. Methodology vs. Tools

…running arguments over functional flow, behavior diagrams, OO, structured, states, QFD,…

“…we don’t need functions, we are doing OO”

An understanding of how they fit into the SE process is necessary so we can know when, and when not to apply them.

Problem: Dental Hygiene

[Armstrong 1993]

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Methodology: Pictures

…picturing the problem space,…

• Help define environment• Actions system will take• Clarify external interfaces & boundaries

Be careful, you don’t depict the solution…

In our dental hygiene case, show what needs to be removed, not how to do it (I.e. no tooth brush, which would constrain potential solutions)

[Armstrong 1993]

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Methodology: Functional Flow

…analysis of how the system is expected to function

• Includes capture, decomposition & sequence of functions• Captures start & end conditions• Variations on partitioning,… In our dental hygiene case, shows serial & parallel tasks)

[Armstrong 1993]

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Methodology: Timelines

…used to analyze & allocatetime constraints

• Identify overlap & race conditions

In our dental hygiene case, shows sequence/timing of events)

[Armstrong 1993]

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Methodology: Requirements Allocation

…shows connections/traceability between requirements, functions, system elements

In our dental hygiene case, show requirement compliance)

[Armstrong 1993]

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Methodology: Schematic Block Diagrams

…capture & communicate potential product architecture, what makes it up, & their interactions

• Shows internal & external interfaces without pushing a particular design• Encourages looking “outside the box”

In our dental hygiene case, shows the preliminary product partitioning)

[Armstrong 1993]

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Methodology: Context Diagrams

…identifies the inputs/outputs for the system

• Helps identify constraints• Identifies stakeholders

In our dental hygiene case, shows all interests in our system

[Armstrong 1993]

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Methodology: Data Flow

…like functional flow, except emphasis on how information flows among system elements.

Helps identify data input/outputconflicts• Data dictionaries

In our dental hygiene case, shows a decomposition of monitoring brushing after meals

[Armstrong 1993]

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Methodology: Behavior Diagrams

…combine data flow and functional flow

• More thorough analysis of actions & what is being acted on in the same diagram. • Support function to system allocations

[Armstrong 1993]

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Methodology: State Diagrams

…analysis of system states or modes

• Identify lock conflicts—on, standby,…• Identify transition problems during design

In our dental hygiene case, shows the system needs to be made ready before it can be used

[Armstrong 1993]

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Methodology: Entity Relationship Diagrams

…analysis of components and how they are related to each other

• Developed for relational database development

In our dental hygiene case, shows the relationship between elements

[Armstrong 1993]

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Methodology: Object Oriented Analysis

…identify what the system will have to deal with as objects

• Similar to mission profiles, schematic block diagrams,…

In our dental hygiene case, shows objects of our dental monitoring system

[Armstrong 1993]

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Methodology: Quality Function Deployment

…qualitative requirements allocation

• bridges gap between qualitative and quantitative • Identify most important product qualities • trade study support tool to focus efforts

In our dental hygiene case, shows relationships of what’s to how’s

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Methodology Summary

• Not all methods included • Pick the tool that gives you the fits the question, not the preconceived answer you are after…ala Jeopardy

…we are going to cover a variety of these tools

[Armstrong 1993]