3. HOW TO PHYSICALLY DESIGN A COMPUTER
BASED INFORMATION SYSTEM
1. Purpose and objectives of the physical design phase:
• First the analyst seeks to design a system that both fulfill requirement and will be friendly to its
end users.
• Second and still very important the analysts seeks to present clear and complete specifications to
the computer programmers and technicians.
2. End users should be involve in the physical data phase:
• End users should be intimately involved in the physical design phase.
• Requirements are transformed into computer inputs, outputs, files/ databases, and program
specifications,
• The end users should at least review key components.
4. 3. Ensure physical design consistency with the business:
• The analyst’s principal concern during the design phase is to ensure that the subsequent design remains
constant with business directions.
4. Fulfill current and projected functional requirements:
• The analysts should have defined functional requirements long before systems design.
• Ensure that the design fulfills those requirements.
• Additional requirements may be introduced during the system design because a computer is used.
• Edit reports for input data and audit trails for transactions are typically added to the basic user defined
requirements.
5. Design all information system components:
1. Data and information:
Specified the content of each data and information flow . we specified the media during the media during the
selection phase. Now we need to physically design the style, organization, and format of all inputs and outputs.
2. Data stores:
We must specify format, organization, and access methods for all files and databases to be used in the computer
based system.
5. 3. End users:
The roles people must play in the new system must be specified. For instance, who will capture and
input data? Who will receive outputs?
4. Methods and procedures:
The sequence of steps and flow of control must be specified.
5. Computer equipment:
The specific hardware configurations specified during the selection phase must be considered as various
other components are designed.
6. Computer program:
Complete programming specifications must be prepared for every program that must be written or
modified.
7. Internal controls:
We must specify internal controls to ensure the security and reliability of the system.
6. HOW TO COMPLETE THE PHYSICAL
DESIGN PHASE
1. Task: design computer files and/ or databases
We must design the corresponding computer files and/or databases. Physical design goes
far beyond the simple layout of the records. Designing files and databases that are
adaptable to future requirements and expansion. Design include record size and storage
volume requirement.
2. Task: design computer outputs
In this task we must format each of those outputs. Transaction outputs will frequently be
designed as preprinted forms onto which transaction details will be printed.
3. Task: design computer inputs
Files and databases are maintained through the timely and accurate input of data. Any time
you input data you can make mistakes. We need to define editing controls to ensure the
accuracy of input data.
7. 4. Task: design the on-line user interface
The idea behind user interface design is to build an easy to learn and use dialogue
around the online input and output screens that were designed in earlier tasks. We are
trying to make it easy for the end-user to understand what the screen is displaying at
any given time.
5. Task: design methods and procedures
The general procedures to be used in the new systems were approved during the
selection phase. The internal controls from the previous tasks must be integrated into
the new systems work flow. The timing of scheduled reports and transactions
processing must be clearly specified.
6. Task: design computer program specifications
this task packages all of the specifications from the previous tasks into computer
program specifications that will guide the computer programmer’s activities during
the constructive phase of the systems development lifecycle.
8. 7. Task: present and review the design
Before the design can be presented, you need to prepare two or more
components.
1. An implementation plan
That presents A proposed schedule for the construction and delivery phases
2. A final cost-benefit analysis
That determines if the design is still feasible. Given the design
specifications and implementations plan you should be able to make much
more refined estimates for the remaining costs.
9. DESIGN BY PROTOTYPING
• Analyst are turning into increasing number to a modern, engineering based
approach called prototyping
• A prototype according to a dictionary is an original or model on which something
is patterned and or a first full scale and usually functional form of a new type or
design of a construction.
• Engineers build prototypes of engines, machines, automobiles, and the like prior
to building actual products.
• Prototypes allow them to isolate problems in both requirements and designs.
10. PROTOTYPING APPROACH
ADVANTAGES
• Prototyping encourages and requires active end users participation. This increases
end users morale and support for the project.
• Interaction and change are a natural consequence of system development that is
end users tend to change their mind. It has often been said that end users don’t
fully know their requirements until they see implemented. If so prototyping
endorses this philosophy.
• An approved prototype is working equivalent to a paper design specification with
one exception. Errors can be detected much earlier.
• Prototyping can increase creativity through quicker user feedback that can lead to
better solutions.
11. • Prototyping accelerates several phases of the lifecycle, possibly bypassing the programmer. In fact
prototyping consolidates parts of phases that normally occur one often the other. These phases includes
the following:
1. Definition:
Each prototype can change not only the design, but the actual requirements until the end users accept
requirements. In many cases requirements can be defined more quickly with this approach.
2. Design:
Screen and report layouts can be very quickly changed until end users accept their designs.
3. Construction:
The very act of prototyping requires construction also known as programming. The analyst
programs if it’s even possible to use that them the prototype.
12. PROTOTYPING APPROACH
DISADVANTAGES
• Prototyping encourages a return to the code implement and repair life cycles that
used to determine information systems.
• There are numerous design issue snot addressed by the prototyping
• Prototyping often leads to premature commitment to a physical design. On other
words the selection phase gets shortchanged.
• When prototyping the scope and complexity of the system can quickly expand
beyond original plans. This can easily get out of control.
• Prototyping often suffers from slower performance then their third generation
language counterparts.
13. PROTOTYPING LANGUAGES AND TOOLS
• Building prototypes makes so much sense that you may wonder why we didn’t always do it.
• This reason is simple the technology wasn’t available.
• Traditional languages like COBOL, FORTRAN, basic, Pascal, and c don’t lend themselves to prototyping.
• Prototyping must be developed and modified quickly, neither of which is possible with third generation
languages.
Simple prototyping tools:
Ads/on-line
Application factory
Datatrive
Focus
Ideal
natural
Intellect
14. RAPID VERSUS SYSTEM PROTOTYPING:
RAPID PROTOTYPING
• Rapid prototyping allows you to create and test input designs, output designs,
terminal dialogues, and simple procedures.
• The technology of rapid prototyping is unique in that it is not built around a
complete applications generator or 4gl
• And instead of being built around a DBMS, it is built around a computerized
data or a project dictionary.
• This dictionary may be a part of a case ( computer- assisted systems
engineering).
15. SYSTEM PROTOTYPING
• System prototyping requires the use of a true fourth- generation language
applications generator. The only difference is that they are completed via
prototyping. The process goes something like this:
1. A prototype databases would be designed, using whatever constraints are
imposed by the 4GL/ AG’s underlying databases.
2. The following task could occur in parallel or in any sequence:
a) Prototype outputs can be created using the report generator of the 4GL/AG.
Reports generator allow new reports to be quickly defined.
16. SYSTEM PROTOTYPING
b) Prototype inputs can be created and generated using the screen
or report generator of the 4GL/ AG. Screens can be changed to
form a dialogue.
3. Once the inputs and outputs are completed, they would be integrated
around some sort of user friendly shell. The most common shell
consists of menus and submenus.
