Design
The design phase decides how the system will operate in terms of the hardware,
software, and network infrastructure that will be in place; the user interface, forms,
and reports that will be used; and the specific programs, databases, and files that
will be needed. Although most of the strategic decisions about the system are made
in the development of the system concept during the analysis phase, the steps in the
design phase determine exactly how the system will operate. The design phase has
four steps:
1. The design strategy must be determined. This clarifies whether the system will
be developed by the company’s own programmers, whether its development will
be outsourced to another firm (usually a consulting firm), or whether the company
will buy an existing software package.
2. This leads to the development of the basic architecture design for the system that
describes the hardware, software, and network infrastructure that will be used. In
most cases, the system will add to or change the infrastructure that already exists
in the organization. The interface design specifies how the users will move
through the system (e.g., by navigation methods such as menus and on-screen
buttons) and the forms and reports that the system will use.
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3. The database and file specifications are developed. These define exactly what
data will be stored and where they will be stored.
4. The analyst team develops the program design, which defines the programs that
need to be written and exactly what each program will do.
This collection of deliverables (architecture design, interface design, database
and file specifications, and program design) is the system specification that is used
by the programming team for implementation. At the end of the design phase, the
feasibility analysis and project plan are reexamined and revised, and another
decision is made by the project sponsor and approval committee about whether to
terminate the project or continue. (See Figure 1-3.)
Implementation
The final phase in the SDLC is the implementation phase, during which the system
is actually built (or purchased, in the case of a packaged software design and
installed). This is the phase that usually gets the most attention, because for most
systems it is the longest and most expensive single part of the development process.
This phase has three steps:
1. System construction is the first step. The system is built and tested to ensure
that it performs as designed. Since the cost of fixing bugs can be immense, testing
is one of the most critical steps in implementation. Most organizations
spend more time and attention on testing than on writing the programs in the
first place.
2. The system is installed. Installation is the process by which the old system is
turned off and the new one is turned on. There are several approaches that may
be used to convert from the old to the new system. One of the most important
aspects of conversion is the training plan, used to teach users how to use the new
system and help manage the changes caused by the new system.
3. The analyst team establishes a support plan for the system. This plan usually
includes a formal or informal post-implementation review, as well as a systematic
way for identifying major and minor changes needed for the system.