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   Implementation Approaches
 Big   bang
  – Code entire system and test in an unstructured
 Top-down
  – Start by implementing modules on top of
    hierarchy and test by coding stubs
 Bottom-up
  – Start by implementing modules on bottom of
    hierarchy and code drivers to test
 Threads
  – Implement and test a minimal set of modules
    implementing a function
     Implementation Approaches
    Advantages and Disadvantages
   Big bang advantages      Big bang disadvantages
    – None                    – Difficult to debug
                              – Much throwaway code
                              – Critical and peripheral
                                modules not distinguished
                              – User does not see product
                                until very late in the
                                development cycle
     Implementation Approaches
    Advantages and Disadvantages
   Top-down advantages             Top-down disadvantages
    – Separately debugged            – Stubs must be written
      modules                        – Low-level, critical
    – System test by                   modules built last
      integrating previously         – Testing upper-level
      debugged modules                 modules is difficult
    – Stubs are easier to code
      than drivers
    – User interfaces are top-
      level modules
     Implementation Approaches
    Advantages and Disadvantages
   Bottom-up advantages          Bottom-up disadvantages
    – Separately debugged          – Drivers must be written
      modules                      – Upper-level, critical
    – System test by                 modules are built last
      integrating previously       – Drivers are more difficult
      debugged modules               to write than stubs
    – Testing upper-level          – User interfaces are top-
      modules is easier              level modules
           Implementation Plan
 Specifies which implementation strategy will
  be employed
 Divides the project into phases
 Specifies a schedule for each phase including
  the following steps for each phase:
  –   Coding
  –   Unit testing
  –   Integration of units
  –   Integration testing
       Activities Involved In
       Implementation Phase
 1) Conduct system Test
 2) Prepare Conversion Plan
 3) Install Databases
 4)Train Users
 5)Convert to New System
     1.Conduct System Testing
 In this test software packages and in – house
  programs have been installed and tested, we need
  to conduct a final system test. All software
  packages, custom- built programs, and many
  existing programs that comprise the new system
  must be tested to ensure that they all work
 This task involves analysts, owners, users, and
     2.Prepare Conversion Plan
 On successful completion of system test, we can
  begin preparations to place the new system into
  operation. Using the design specifications for the
  new system, the system analyst will develop a
  detailed conversion plan. This plan will identify
 Database to be installed, end – user training and
  documentation that needed to be developed, and a
  strategy for converting from the old system to the
  new system.
    2.Prepare Conversion Plan
 The  conversion plan may include one of the
  following commonly used installation
 1) Abrupt Cut-over
 2) Parallel Conversion
 3) Location Conversion
 4) Staged Conversion
            3.Install Databases
 In the previous phase we built and tested the
  database. To place the system into operation we
  need fully loaded databases. The purpose of this
  task is to populate the new systems databases with
  existing database from the old system.
 System builders play a primary role in this
                 4.Train Users
•   Converting to a new system necessitates that
    system users be trained and provided with
    documentation that guides them through using the
    new system. Training can be performed one on
    one; however group training is preferred.
•   This task will be completed by the system analysts
    and involves system owners and users.
           5.Convert to New System
 Conversion to the new system from old system is a
  significant milestone. After conversion, the ownership of
  the system officially transfers from the analysts and
  programmers to the end users. The analyst completes this
  task by carrying out the
 conversion plan Recall that the conversion plan includes
  detailed installation strategies to follow for converting
  from the existing to the new production information
 This task involves the system owners, users, analysts,
  designers, and builders
            User Acceptance Testing
 Goal: Demonstrate system is ready for
  operational use
   – Many tests can be taken from integration testing
   – Acceptance test is performed by the client, not by the
 Majority of all bugs in software is typically found by the
  client after the system is in use, not by the developers or
  testers. Therefore two kinds of additional tests:
           User Acceptance Testing
 Alpha   test:
  – Sponsor uses the software at the developer’s site.
  – Software used in a controlled setting, with the
    developer always ready to fix bugs.
 Beta test:
 Conducted at sponsor’s site (developer is not
 Software gets a realistic workout in target
  environ- ment
 Potential customer might get discouraged
                 Data Conversion
 Data  Conversion is defined as the changing of the
  data structure to accommodate new or different
  needs for the data
 Explanation:
  Different operating systems have different application
  software, and each application normally has its own
  internal way of saving data. There are some standards
  such as CSV files for databases and RTF files for word
  processing text, however, these are few and far between
  and often only save the basic information rather than the
  full structure.
                  Data Conversion
   Simple Data Conversion
   Simple data conversion can be defined as the
    transferring of files between different operating
    systems or backup routines without converting the
   Examples:

   Transferring data from Unix backup tapes to a
    Windows compatible CD. Unix systems use a line
    feed and no carriage return. In this case the line
    feed would be changed to a carriage return.
   Transferring data between different PC backups
              Change Management
   Computer based systems are dynamic.As the
    business Environment changes, there is a need
    of some changes to the information
    system.The changes occur not only during the
    study,design,and development phases of the
    life cycle of the system. In this process there
    are two two elements that are essential to the
    management of change.
   They are
   1) The performance review board, which can
    make management – level decisions about
    system modifications
   2) Baseline documentation, which can be
    referred to, to determine the extent and impact
    of proposed modifications.
            Change Management
In addition to the conduct of post –installation
And periodic reviews, the PRB also must evaluate
  requests for modifications of the operational
  system.some requests will be planned.others will
  be unplanned.some will be extremely
  significant.The PRB should not be involved on a
  continuing daily basis, but only when
  requirements for system modification rise above a
  certain threshold of importance.

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