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11. APPROACHES TO SYSTEMS-BUILDING. Learning Objectives. Appraise system building alternatives Compare strengths, weaknesses of approaches Assess solutions to problems created by approaches Describe tools, methodologies of systems development *. System Lifecycle.

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Presentation Transcript
slide1

11.

APPROACHES TO

SYSTEMS-BUILDING

learning objectives
Learning Objectives
  • Appraise system building alternatives
  • Compare strengths, weaknesses of approaches
  • Assess solutions to problems created by approaches
  • Describe tools, methodologies of systems development

*

system lifecycle
System Lifecycle
  • Project definition:is there a problem? Can it be solved with a project?
  • System study:analyze problems in existing systems; Define objectives evaluate alternatives
  • Design:logical & physical specifications for systems solution
  • Programming:develop software code

*

system lifecycle4
System Lifecycle
  • Installation:construct, test, train, convert to new system
  • Post-installation:on-going evaluation, modifications for improvement to meet new requirements

These steps are necessary for large, complex systems & projects

*

system lifecycle5
System Lifecycle
  • Can be costly, time consuming
  • May encourage freezing specifications early in development
  • May not be suitable for small, less structured systems

*

alternative system building approaches
Alternative System-building Approaches
  • Prototyping
  • Application software packages
  • End-user development
  • Outsourcing

*

prototyping
Prototyping

Process of building experimental system to demonstrate, evaluate approach; Users refine needs

  • Prototype:preliminary working version of information system for demonstration, evaluation purposes
  • Iterative process

*

application software packages
Application Software Packages

Prewritten, pre-coded application software, commercially available for sale or lease

  • Geared to common requirements (significant few; Canned functions)
  • Customization:modification of software to meet organization’s needs (trivial many; Use programming tools)
  • Must weigh costs / benefits

*

selected examples of application programs
Selected Examples Of Application Programs

Accounts receivable; Bond & stock management; Computer-aided design (CAD) ; document imaging;E- mail; Enterprise.Resource planning (ERP); Groupware; Health care; Hotel.Management; Internet telephone; Inventory control; Job costing; Library systems; Life insurance; Mailing labels; Mathematical / statistical modeling; Order processing; Payroll; Process control;Tax accounting; Web browser;Word processing; Banner

*

effects of customizing software on total implementation costs

10

8

6

TOTAL IMPLEMENTATION

COSTS

4

2

0

0.5

1

2

3

4

5

% LINES OF CODE CONVERTED

Effects Of Customizing Software On Total Implementation Costs
end user development
End-user Development

End-users develop information system themselves, with little help from technical specialists; Using 4th generation tools

(Part III of this course)

*

end user development12
End-user Development

Strengths:

  • Improved requirements determination
  • Increased user involvement & satisfaction
  • Reduced application backlog

*

end user development13
End-user Development

Weaknesses:

  • Relatively inefficient
  • Slow transaction processing
  • May carry high/hidden cost
  • Nonprocedural approach makes it difficult for others to understand or update

Managers are not really programmers; Take them away from their REAL work.

*

outsourcing
Outsourcing

Contracting:

  • Computer center operations
  • Telecommunications networks
  • Application development

To external vendors (allow others to hold you by your throat?)

*

system building methodologies
System Building Methodologies
  • Structured methodologies (ER approach to SDLC)
  • Object-oriented software development (BMIS 342)
  • Computer aided software engineering (CASE, BMIS 342)
  • System analysis and design (BMIS 444)

*

structured methodologies
Structured Methodologies

Top down, step by step, each step builds on previous

  • Structured analysis
  • Structured design
  • Structured programming
  • Flowcharts

*

structured analysis
Structured Analysis
  • Defines system inputs, processes, outputs
  • Partitions system into subsystems or modules
  • Logical, graphical model of information flow
  • Data flow diagram:graphical display of component processes, flow of data

*

slide18

SYMBOLS FOR DATA FLOW DIAGRAMS (DFD):

DATA FLOW

PROCESS

SOURCE

OR SINK

FILE

slide19

CUSTOMER

FILE

PAYMENT

FILE

DATA FLOW DIAGRAM:

GENERATE

BALANCE

GENERATE

BILL

GENERATE

REPORT

CUSTOMER

MANAGER

structured analysis20
Structured Analysis
  • Data dictionary:controlled definitions of descriptions of all data, such as variable names & types of data
  • Process specifications:describes logic of processes at module level

*

slide22

PROCESS A

SEQUENCE

PROCESS B

R

TRUE

PROCESS E

TRUE

PROCESS D

PROCESS C

S

SELECTION

ITERATION

Program flowchart:

slide23

1

START

2

READ

PRINT

>$10,000

REPORT

PROCESS A

<$10,000

2

MORE?

PROCESS B

1

END

PROGRAM FLOWCHART:

object oriented software development
Object - Oriented Software Development
  • De-emphasizes procedures (“what needs to be done” rather than “how to do it”)
  • Shifts focus from models & data toobjects, which combine data & procedures
  • “Reusable” objects

Reduces development time & cost

*

software engineering
Software Engineering
  • The establishment and use of sound engineering principles in order to obtain economically software that is reliable and works efficiently on real machines
  • Engineering: solution based on theoretical knowledge
software re engineering
Software Reengineering
  • Salvages & upgrades aging software
  • Delays expensive replacement
  • Reverse engineering:converting existing programs, files, database for use in new applications

*

software reengineering
Software Reengineering
  • Revise design & program specifications
  • Forward engineering:use revised materials to generate new, structured code; Structured & maintainable system

*