information systems definedsmall enterprise characteristicsInformation needs of the small enterprisethe systems development life cyclecomputer information system componentsthe role of the analystmethodologies, tools, and techniquesthe enhanced SDLCportfolio project

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section IIntroduction

Systems definition

• a set of entities, real or abstract, comprising a whole where each component interacts with or is related to at least one other component.

• Any object which has no relation with any other element of the system is not part of that system but rather of the system environment.

• A subsystem then is a set of elements, which is a system itself, and a part of the whole system.

• In other words . . .

Systems definition

• A system is composed of regularly interacting or interrelating groups of activities/parts which, when taken together, form a new whole. In most cases this whole has properties which cannot be found in the constituent elements.. . .

Systems definition example

Systems definition exampleCar as a System

• Car– Propulsion (engine)

• Fuel• Electrical

– Control• Braking• Steering• Acceleration

– Signal

– Safety• Starting• Seatbelts• Air bags

– Comfort• Temperature• Entertainment

– Radio

– TV / Video

– Monitoring• Speedometer• Odometer• Temperature• Oil

The concept of a system

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How do the “rules” change

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How do the “rules” change

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Systems definition exampleSystem: An interrelated set of components, with an identifiable boundary, working together for some purpose

General System Depiction

Environment: Everything external to a system that interacts with the system.

General System Depiction

Boundary: The line that marks the inside and outside of a system and that sets off the system from its environment.

General System Depiction

Components: An irreducible part or aggregation of parts that make up a system, also called a subsystem..

General System Depiction

Interrelationship: Dependence of one subsystem on one or more subsystems.

General System Depiction

Input: Whatever a system takes from its environment in order to fulfill its purpose.

General System Depiction

Output: Whatever a system returns to its environment in order to fulfill its purpose.

General System Depiction

Interfaces: Point of contact where a system meets its environment or where subsystems meet each other.

Information Systems Defined

• An information system is a well-coordinated collection of resources that gather and transform data into information products and services that help the enterprise perform its designed functions

• An information system hierarchy associates different classifications of information systems with different audiences

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Information System Hierarchy

Information Systems Defined

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Three significant trends influence the evolution of information systems and provide opportunities for the entrepreneurial systems analyst:

• The emergence of small enterprise computing• The Internet as a dominating technology• The maturation of application software

Small Enterprise Characteristics

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The following small enterprise characteristics influence the analyst’s work:

• Owner participation• Economic constraints• Competitive pressures

Information Needs of the Small Enterprise

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The following are common information needs of any enterprise:

• Production and inventory• Personnel• Financial reporting• Marketing, sales, and service• Customer relations

Computing Terminology

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TECHNOTE 1-1

Several software products are integral to the analyst’s work:

•Off-the shelf application software

•Software suites

•Computer assisted systems engineering (CASE)

•Object-oriented application software

The Systems Development Life Cycle

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The systems development life cycle (SDLC) consists of five major phases:

• Analysis• Design• Development• Implementation• Maintenance

The Circular SDLC

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The Recurring SDLC

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Information System Components

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There are six major information system components:

• People• Procedures• Software• Hardware• Networks• Data

Reference Figure 1-7: Information System Components

Software Classifications

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TECHNOTE 1-2

System Software•Operating systems

•Firmware

•Utility

Application Software•Horizontal

•Vertical

•Turnkey

Customizable Software•Third-generation programming languages

•Fourth-generation programming language (4GL)

•Object-oriented programming language

•4GL products

The Role of the Analyst

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• An agent of change• A problem-solving strategist• A group facilitator

• Four Sets of Analytical Skills– Systems Thinking– Organizational Knowledge– Problem Identification– Problem Analyzing and Solving

The Blurred Proportional SDLC

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Methodologies, Tools, and Techniques

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• CASE Tools• Systems Architect• Alternatives to CASE

technologies (VISIO)

The Enhanced SDLC

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The enhanced SDLC embodies several important concepts:

• The recurring nature of the SDLC• The blending of several phases of the SDLC• The influence of the user throughout the SDLC• The addition of many powerful tools to assist

the analyst

The Enhanced SDLC

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Chapter Summary (1/3)

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• Small enterprise, PC-based computing should rely on proven systems theory and techniques

• The small enterprise approach presents special advantages for an introductory study of systems analysis

• The systems development life cycle provides a framework for creating a small enterprise information system

Chapter Summary (2/3)

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• There are five phases of the SDLC:• Analysis• Design• Development• Implementation• Maintenance

• There are six components of an information system• People• Procedures• Software• Hardware• Networks• Data

Chapter Summary (3/3)

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• A systems analyst is:– An agent of change– A problem solving strategist– A group facilitator

• Characteristics of a System – Components– Interrelated Components– Boundary– Purpose– Environment– Interfaces– Input– Output– Constraints