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Lecture 11: System Design

and Development

K S Rajan

IIIT, Hyderabad

A Synthesis

1. WHAT are the boundary conditions and constraints imposed by the

User on a system, product, or service in terms of missions within a

prescribed OPERATING ENVIRONMENT?

2. Given the set of boundary conditions and constraints, HOW does

the User envision deploying, operating, and supporting the system,

product, or service to perform its missions within specific time

limitations, if applicable?

3. Given the deployment, operation, support, and time constraints

planned for the system, product, or service, WHAT is the set of

outcome-based behaviors and responses required of the system to

accomplish its missions?

4. Given the set of outcome-based behaviors and responses required

of the system to accomplish its mission, HOW is the deliverable

system, product, or service to be physically implemented to perform

those missions and demonstrate?

Design and Development Practices

• System Development Strategies Practices

• System Specification Practices

• System Design and Development Practices

• Decision Support Practices

• System Verification and Validation Practices

• System Deployment, Operations, and

Support Practices

System Flow – a perspective System Development Phase

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• System Design Process Strategy

– highly iterative, topdown/bottom-up/lateral process

• Select the right Implementation approach

– Level of understanding of the problem and solution

spaces.

– The maturity of the SPS requirements.

– Level of risk.

– Critical operational or technical issues (COIs/CTIs).

– Eg: Waterfall, Incremental Development, and Spiral

Development

Engineering Design Strategy

SITE

System Integration, Test and

Evaluation (SITE) “V” Model

System Development Spiral Another Design Framework

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System Development Models

1. The Waterfall Development Model

2. The Evolutionary Development Model

3. The Incremental Development Model

4. The Spiral Development Model

Waterfall Model

Evolutionary Developmental

Models

Dr. Boehm notes the following points:

• Fallacy 1: The Evolutionary Development Model

is difficult to delineate from the build, test, and fix

approaches “whose spaghetti code and lack of

planning were the initial motivation for the

“waterfall model.”

• Fallacy 2: The Evolutionary Development Model

stemmed from the “often unrealistic” assumption

that the system would always provide the

flexibility to accommodate unplanned evolution

paths.

Spiral Developmental Model

Incremental Development StrategySystem Specification Practices

Requirements that bound the User’s solution space subject to -

technology,

cost,

schedule,

support, and

risk constraints.

Specification requirements have to be analyzed, derived, developed, and reviewed.

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Specification DevelopmentRequirements vs. Operational

States

System Design and Development

Practices

Need to understand -

• the operational utility, suitability, effectiveness,

and availability requirements;

• formulation of domain solutions;

• selection of a system architecture;

• configuration identification;

• system interface design;

• standards and conventions; and

• design and development documentation.

Approaches

Organizations and SEs employ a number of

approaches to development of specifications.

Typical approaches include:

1. Feature-based approach

2. Reuse-based approach

3. Performance-based approach

4. Model-based approach

Decision Support Practices

• statistical variation influences on system

design;

• system performance budgets and margins;

• system reliability, availability, and

maintainability;

• system modeling and simulation; and

• trade study analysis of alternatives

System Verification and Validation

Practices

1. Is the system being designed and

developed RIGHT—in accordance with

the contract requirements and

2. Does the system satisfy the user’s

operational needs?

• Technical reviews

• System integration, test, and evaluation

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System Deployment, Operations, and

Support PracticesSE and System Analyst work doesn’t end with Operationalization of the System. He further needs to

1. Assess mission outcomes and performance

2. Suggest corrective actions

3. Study it for future systems and capabilities requirements

• Check How a system is deployed including site selection, development, and activation;

• Identify Key considerations for System integration into a higher level system;

• Address how system deficiencies are investigated – a basis for acquisition requirements for new systems, products, or services; and

• Investigate key engineering considerations that must be translated into specification requirements for new systems.