Building and maintaining systems
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Building and Maintaining Systems. Building and Maintaining Information Systems. Phases of information systems Alternative approaches for building information systems Traditional SDLC Prototypes Application Packages End-User Development How to choose which methods to use?.

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Building and Maintaining Systems

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Building and maintaining systems

Building and Maintaining Systems


Building and maintaining information systems

Building and Maintaining Information Systems

  • Phases of information systems

  • Alternative approaches for building information systems

  • Traditional SDLC

  • Prototypes

  • Application Packages

  • End-User Development

  • How to choose which methods to use?


Introductory case microsoft

Introductory case (Microsoft)…

  • “Big system” development

  • How does this compare to small, focused projects?

  • How does this compare to the open source philosophy?


Phases of any information system

Phases of any information system

  • Remember these? From the first chapter, and it was a mid-term question…

  • Phases (generically speaking)

    • Initiation

    • Development

    • Implementation

    • Operation and maintenance


Cost of errors based on time of detection

Cost of errors, based on time of detection


How are these phases linked

How are these phases linked?


Alternative approaches for building systems

Alternative approaches for building systems

  • Approaches

    • Traditional SDLC

    • Prototypes

    • Application Packages

    • End-user development

  • Let’s look at each of these in more detail…


What are the differences

What are the differences?

TRADITIONAL SYSTEM LIFE CYCLE

Issue addressed: Control

Summary: Go through a fixed sequence of steps with signoffs after each step and careful documents.

PROTOTYPE

Issue addressed: Knowledge

Summary: Quickly develop a working model of the system; use the model to gain experience and decide how the final system should operate.

APPLICATION PACKAGES

Issue addressed: Resources and timing

Summary: Purchase an existing information system from a vendor; customize the system if necessary.

END USER DEVELOPMENT

Issue addressed: Responsiveness

Summary: Provide tools and support that make it practical for end users to develop their own information systems.


Traditional sdlc

Traditional SDLC

  • Initiation

    • Feasibility study

      • Economic, technical and organizational

    • Functional spec

    • Project plan

  • Development

    • Look at the diagram on the next slide…


Steps in development

Steps in Development


Formal development in action

Formal development in action…

  • The IMS project


Traditional sdlc1

Traditional SDLC

  • Implementation

    • Is there a similar breakdown of tasks?


Implementation

Implementation


Traditional sdlc2

Traditional SDLC

  • Operation and maintenance


Prototypes

Prototypes

  • Phases

  • Advantages & disadvantages

    • Used when there is not a clear picture of what is needed in a system

    • Iterative “quick & dirty” mockups


Prototype phases

Prototype phases…

INITIATION

Users and developers agree to develop a prototype because they need experience with a working model before designing a final system.

DEVELOPMENT

Working iteratively with users, a prototype is developed and improved. Later, decide whether to complete the prototype or switch to a traditional life cycle.

IMPLEMENTATION

Accomplish parts of implementation along with development as users work with the prototype system. Dispel skepticism about whether the system will meet users’ needs.

OPERATION AND MAINTENANCE

May be similar to a traditional life cycle. May require less maintenance because the system fits users’ needs more accurately. May require more maintenance because the system is not constructed as well.


Prototypes iterative development

Prototypes – iterative development


Application packages cots

Application packages (COTS)

  • Phases

  • Advantages & disadvantages


Application package phases

Application package phases

INITIATION

May start with user’s or manager’s recognition of a business problem or with a sales call from a vendor.

DEVELOPMENT

The vendor develops the software, although the purchase still performs some typical development activities, such as determining detailed requirements. Development may include customization of the software and user documentation.

IMPLEMENTATION

Implementation starts by deciding exactly how the package will be used. It often relies on the vendor’s staff because they have the greatest knowledge of the system.

OPERATION AND MAINTENANCE

Operation occurs as it would with a traditional life cycle. Maintenance is different because the vendor maintains the software based on requests from customers and demands of the market.


Selecting an application package

Selecting an application package

A

B

C

A

B

C

APPLICATION FEATURES

completeness

quality of reports

ease of use

documentation

TECHNICAL FEATURES

use of DBMS

transportability

expandability

VENDOR COMPARISON

financial strength

management strength

committment to product

ECONOMIC COMPARISON

purchase price

maintenance contract

consulting charges

conversion cost

Total weighted score

WEIGHT

2.5

1.0

2.3

2.8

2.8

0.8

1.2

2.0

1.3

2.6

2.0

1.5

0.6

2.3

SCORE

9 7 8

9 5 9

5 9 6

3 9 7

8 7 3

2 5 6

4 5 5

9 7 5

6 9 8

4 7 9

7 5 7

7 7 8

5 6 8

5 3 5

WEIGHTED SCORE

22.5 17.3 20.0

9.0 5.0 9.0

11.5 20.7 19.6

8.4 25.2 19.6

22.4 19.6 8.4

1.6 4.0 4.8

4.8 6.0 6.0

18.0 14.0 10.0

7.8 11.7 10.4

10.4 18.2 23.4

14.0 10.0 14.0

10.5 10.5 12.0

3.0 3.6 4.8

11.5 6.9 11.5

155.4 172.9 167.7


End user development

End-user development

  • Phases

  • Supporting the users

  • Advantages & disadvantages


End user system phases

End-user system phases

INITIATION

Because the user will develop the information system, a formal functional specification is unnecessary.

DEVELOPMENT

The user develops the system using tools that do not require a professional level of programming knowledge. Information systems that are critical to the company or have many users require more extensive testing, documentation, and usage procedures.

IMPLEMENTATION

Implementation is simplified because the developer is the user.

OPERATION AND MAINTENANCE

End users are responsible. Long-term maintenance and technical quality become larger issues because the end users have other work to do and are not professional programmers.


Deciding which methods to use

Deciding which methods to use

  • Comparing…

  • Synthesizing to get the right balance…

    • It’s not all or nothing


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