Chapter 12_ Building and Maintaining Systems by hcj

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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?
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
 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
How are these phases linked?
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?
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
 Initiation
   – Feasibility study
      • Economic, technical and organizational
   – Functional spec
   – Project plan
 Development
  – Look at the diagram on the next slide…
Steps in Development
Formal development in action…
 The IMS project
Traditional SDLC
 Implementation
   – Is there a similar breakdown of tasks?
Implementation
Traditional SDLC
 Operation and maintenance
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…
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
Application packages (COTS)
 Phases
 Advantages & disadvantages
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
                                  A   B   C    A       B      C
APPLICATION FEATURES     WEIGHT   SCORE        WEIGHTED SCORE
completeness             2.5      9   7   8    22.5 17.3  20.0
quality of reports       1.0      9   5   9     9.0   5.0  9.0
ease of use              2.3      5   9   6    11.5  20.7 19.6
documentation            2.8      3   9   7     8.4  25.2 19.6
TECHNICAL FEATURES
use of DBMS              2.8      8   7   3    22.4    19.6       8.4
transportability         0.8      2   5   6    1.6      4.0       4.8
expandability            1.2      4   5   5    4.8      6.0       6.0
VENDOR COMPARISON
financial strength       2.0      9   7   5    18.0    14.0   10.0
management strength      1.3      6   9   8     7.8    11.7   10.4
committment to product   2.6      4   7   9    10.4    18.2   23.4
ECONOMIC COMPARISON
purchase price           2.0      7   5   7    14.0    10.0   14.0
maintenance contract     1.5      7   7   8    10.5    10.5   12.0
consulting charges       0.6      5   6    8    3.0     3.6    4.8
conversion cost          2.3      5   3    5   11.5     6.9   11.5

Total weighted score                           155.4   172.9 167.7
End-user development
 Phases
 Supporting the users
 Advantages & disadvantages
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
 Comparing…
 Synthesizing to get the right balance…
   – It’s not all or nothing

								
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