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					Chapter Twelve


   Approaches to Systems-Building
The Traditional Systems
Lifestyle
   The systems lifecycle is a traditional
    methodology for developing an
    information systems that partitions the
    systems development process into formal
    stages that must be completed sequentially
    with a very formal division of labor
    between end users and information systems
    specialists.
Stages of the System Lifecycle
   Project Definition
   Systems Study
   Design
   Programming
   Installation
   Post-Implementation
Alternative System-Building
Approaches
   Prototyping
   Application Software Packages
   End-User Development
   Outsourcing
Prototyping
   Prototyping – the process of building an
    experimental system quickly and
    inexpensively for demonstration and
    evaluation so that users can better
    determine information requirements.
   Prototype – The preliminary version of an
    information system for demonstration and
    evaluation purposes.
Steps in Prototyping
   1. Identify the user’s basic requirements.
   2. Develop and initial prototype.
   3. Use the prototype and determine how
    well it meets the end-user’s needs.
   4. Revise and enhance the prototype.
Advantages of Prototyping
   most useful when there is uncertainty
    regarding requirements.
   It is valuable for developing the end-user
    interface.
   Encourages end-user development in the
    process.
Disadvantages of Prototyping
   Prototyping is better suited for small
    applications. Large systems would have to
    be subdivided in order to prototype and it
    would have to occur one at time.
   Rapid prototyping can gloss over essential
    steps in the process.Mgmt might view a
    working prototype as ready go and ignore
    the necessary testing process.
Application Software Packages
   A set of prewritten, precoded application
    software programs that are commercially
    available for sale or lease.
       Many examples AR, Email, Doc Imaging, etc
   ASP are good because they are already pretested
    and can be implemented almost immediately.
   ASP can be bad if you have a low level of
    customization. Also if you do have to
    customize—if you have to do a lot, it might be
    better to create your own.
End-User Development
   The development of information systems by end
    users with little or no formal assistance from
    technical specialists.
       See figure 12-5 page 379
   Mgmt Benefits
       Improved requirements determination
       Increased user involvement and satisfaction
       Reduced application backlog
   Challenges
       Poses challenges because it occurs outside of
        traditional methods.
       Control of data is lost, particular when users create
        their own data files, they get hard to access
Outsourcing
   The practice of contracting computer center
    operations, telecommunications networks,
    or applications development to external
    vendors.
   When to use outsourcing
       To reduce costs of offload some of the work
        of the IS dept.
       When the firm’s IS capabilities are limited,
        ineffective, or inferior
Outsourcing Cont.
   When to use outsourcing
       To improve the contribution of IT to business
        performance.
       To create new sources of revenue and profit, to
        leverage increasing IT costs.
   Solution Centers
       Facility operated by a commercial vendor which
        provides clients with models for solving common IS
        Problems
   Why not Outsource?
System Building Methodologies
   Development methodology – a collection
    of methods, one or more for every activity
    within every phase of a development
    project.
   Structured methodology – refers to the fact
    that techniques are carefully drawn up,
    often step-by-step, with each step building
    on a previous one
Structured Methodologies
   Structured Analysis
       Method for designing inputs, process, etc in a logical
        form
   Structured Design
       A discipline, encompassing a set of rules for
        designing a system from the top down in a
        hierarchical fashion
   Structured Programming
       A discipline for organizing and coding programs that
        simplifies the control paths, uses basic control
        structures and modules that have one entry and one
        exit.
Limitations of Structured
(Traditional) Methods
   They can be inflexible
   They can be time-consuming
   If any changes need to occur then many
    steps are involved
   They are function-oriented instead of data-
    oriented.
Object-Oriented Software
Development
   An approach to software development that
    deemphasizes procedures and shifts the
    focus from modeling business processes
    and data to combining data and procedures
    to creating objects.
Computer-Aided Software
Development
   The automation of step-by-step
    methodologies for software and systems
    development to reduce the amount of
    repetitive work the developer needs to do.
Rapid Application Development
   Process for developing systems in a very
    short time period by using prototyping,
    fourth-generation tools, and close
    teamwork among systems specialists.
   Related to JAD – joint application
    development- same thing except end-users
    are involved in JAD
Software Reengineering
   A methodology that addresses the problem
    of aging software by salvaging and
    upgrading it so that the users can avoid a
    long and expensive replacement project.
Reverse Engineering
   The process of converting existing
    programs, files, and databases into
    corresponding design-level components
    that can then be used to create new
    applications.
   Forward Engineering
       The final step in reengineering when revised
        specs are used to generate new structured
        code for a maintainable system.
Concluding Questions
   Why is selecting a system development
    approach important?
   Who should participate in the process?

				
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posted:9/15/2012
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