1. Building and Maintaining Systems

2. 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?

3. Introductory case (Microsoft)…
“Big system” development
How does this compare to small, focused projects?
How does this compare to the open source philosophy?

4. 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

5. Cost of errors, based on time of detection

6. How are these phases linked?

7. Alternative approaches for building systems
Traditional SDLC
Prototypes
Application Packages
End-user development
Let’s look at each of these in more detail…

8. 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.

9. Traditional SDLC Initiation Development Feasibility study
Economic, technical and organizational
Functional spec
Project plan
Development
Look at the diagram on the next slide…

10. Steps in Development

11. Formal development in action…
The IMS project

12. Traditional SDLC
Implementation
Is there a similar breakdown of tasks?

13. Implementation

14. Traditional SDLC
Operation and maintenance

15. Prototypes Phases Advantages & disadvantages
Used when there is not a clear picture of what is needed in a system
Iterative “quick & dirty” mockups

16. Prototype phases… INITIATION DEVELOPMENT IMPLEMENTATION
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.

17. Prototypes – iterative development

18. Application packages (COTS)
Phases
Advantages & disadvantages

19. 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.

20. Selecting an application packageB 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
0.8
1.2
2.0
1.3
2.6
1.5
0.6
SCORE
WEIGHTED SCORE

21. End-user development Phases Supporting the users
Advantages & disadvantages

22. 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.

23. Deciding which methods to use
Comparing…
Synthesizing to get the right balance…
It’s not all or nothing